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Opportunities and Challenges in High Pressure Processing of Foods
By Rastogi, N K; Raghavarao, K S M S; Balasubramaniam, V M; Niranjan, K; Knorr, D
Consumers increasingly demand convenience foods of the highest quality in terms of natural flavor and taste, and which are free from additives and preservatives. This demand has triggered the need for the development of a number of nonthermal approaches to food processing, of which high-pressure technology has proven to be very valuable. A number of recent publications have demonstrated novel and diverse uses of this technology. Its novel features, which include destruction of microorganisms at room temperature or lower, have made the technology commercially attractive. Enzymes and even spore forming bacteria can be inactivated by the application of pressure-thermal combinations, This review aims to identify the opportunities and challenges associated with this technology. In addition to discussing the effects of high pressure on food components, this review covers the combined effects of high pressure processing with: gamma irradiation, alternating current, ultrasound, and carbon dioxide or anti-microbial treatment. Further, the applications of this technology in various sectors-fruits and vegetables, dairy, and meat processing-have been dealt with extensively. The integration of high-pressure with other matured processing operations such as blanching, dehydration, osmotic dehydration, rehydration, frying, freezing / thawing and solid- liquid extraction has been shown to open up new processing options. The key challenges identified include: heat transfer problems and resulting non-uniformity in processing, obtaining reliable and reproducible data for process validation, lack of detailed knowledge about the interaction between high pressure, and a number of food constituents, packaging and statutory issues.
Keywords high pressure, food processing, non-thermal processing
Consumers demand high quality and convenient products with natural flavor and taste, and greatly appreciate the fresh appearance of minimally processed food. Besides, they look for safe and natural products without additives such as preservatives and humectants. In order to harmonize or blend all these demands without compromising the safety of the products, it is necessary to implement newer preservation technologies in the food industry. Although the fact that “high pressure kills microorganisms and preserves food” was discovered way back in 1899 and has been used with success in chemical, ceramic, carbon allotropy, steel/alloy, composite materials and plastic industries for decades, it was only in late 1980′s that its commercial benefits became available to the food processing industries. High pressure processing (HPP) is similar in concept to cold isostatic pressing of metals and ceramics, except that it demands much higher pressures, faster cycling, high capacity, and sanitation (Zimmerman and Bergman, 1993; Mertens and Deplace, 1993). Hite (1899) investigated the application of high pressure as a means of preserving milk, and later extended the study to preserve fruits and vegetables (Hite, Giddings, and Weakly, 1914). It then took almost eighty years for Japan to re- discover the application of high-pressure in food processing. The use of this technology has come about so quickly that it took only three years for two Japanese companies to launch products, which were processed using this technology. The ability of high pressure to inactivate microorganisms and spoilage catalyzing enzymes, whilst retaining other quality attributes, has encouraged Japanese and American food companies to introduce high pressure processed foods in the market (Mermelstein, 1997; Hendrickx, Ludikhuyze, Broeck, and Weemaes, 1998). The first high pressure processed foods were introduced to the Japanese market in 1990 by Meidi-ya, who have been marketing a line of jams, jellies, and sauces packaged and processed without application of heat (Thakur and Nelson, 1998). Other products include fruit preparations, fruit juices, rice cakes, and raw squid in Japan; fruit juices, especially apple and orange juice, in France and Portugal; and guacamole and oysters in the USA (Hugas, Garcia, and Monfort, 2002). In addition to food preservation, high- pressure treatment can result in food products acquiring novel structure and texture, and hence can be used to develop new products (Hayashi, 1990) or increase the functionality of certain ingredients. Depending on the operating parameters and the scale of operation, the cost of highpressure treatment is typically around US$ 0.05-0.5 per liter or kilogram, the lower value being comparable to the cost of thermal processing (Thakur and Nelson, 1998; Balasubramaniam, 2003).
The non-availability of suitable equipment encumbered early applications of high pressure. However, recent progress in equipment design has ensured worldwide recognition of the potential for such a technology in food processing (Could, 1995; Galazka and Ledward, 1995; Balci and Wilbey, 1999). Today, high-pressure technology is acknowledged to have the promise of producing a very wide range of products, whilst simultaneously showing potential for creating a new generation of value added foods. In general, high-pressure technology can supplement conventional thermal processing for reducing microbial load, or substitute the use of chemical preservatives (Rastogi, Subramanian, and Raghavarao, 1994).
Over the past two decades, this technology has attracted considerable research attention, mainly relating to: i) the extension of keeping quality (Cheftel, 1995; Farkas and Hoover, 2001), ii) changing the physical and functional properties of food systems (Cheftel, 1992), and iii) exploiting the anomalous phase transitions of water under extreme pressures, e.g. lowering of freezing point with increasing pressures (Kalichevsky, Knorr, and Lillford, 1995; Knorr, Schlueter, and Heinz, 1998). The key advantages of this technology can be summarized as follows:
1. it enables food processing at ambient temperature or even lower temperatures;
2. it enables instant transmittance of pressure throughout the system, irrespective of size and geometry, thereby making size reduction optional, which can be a great advantage;
3. it causes microbial death whilst virtually eliminating heat damage and the use of chemical preservatives/additives, thereby leading to improvements in the overall quality of foods; and
4. it can be used to create ingredients with novel functional properties.
The effect of high pressure on microorganisms and proteins/ enzymes was observed to be similar to that of high temperature. As mentioned above, high pressure processing enables transmittance of pressure rapidly and uniformly throughout the food. Consequently, the problems of spatial variations in preservation treatments associated with heat, microwave, or radiation penetration are not evident in pressure-processed products. The application of high pressure increases the temperature of the liquid component of the food by approximately 3C per 100 MPa. If the food contains a significant amount of fat, such as butter or cream, the temperature rise is greater (8-9C/100 MPa) (Rasanayagam, Balasubramaniam, Ting, Sizer, Bush, and Anderson, 2003). Foods cool down to their original temperature on decompression if no heat is lost to (or gained from) the walls of the pressure vessel during the holding stage. The temperature distribution during the pressure-holding period can change depending on heat transfer across the walls of the pressure vessel, which must be held at the desired temperature for achieving truly isothermal conditions. In the case of some proteins, a gel is formed when the rate of compression is slow, whereas a precipitate is formed when the rate is fast. High pressure can cause structural changes in structurally fragile foods containing entrapped air such as strawberries or lettuce. Cell deformation and cell damage can result in softening and cell serum loss. Compression may also shift the pH depending on the imposed pressure. Heremans (1995) indicated a lowering of pH in apple juice by 0.2 units per 100 MPa increase in pressure. In combined thermal and pressure treatment processes, Meyer (2000) proposed that the heat of compression could be used effectively, since the temperature of the product can be raised from 70-90C to 105-120C by a compression to 700 MPa, and brought back to the initial temperature by decompression.
As a thermodynamic parameter, pressure has far-reaching effects on the conformation of macromolecules, the transition temperature of lipids and water, and a number of chemical reactions (Cheftel, 1992; Tauscher, 1995). Phenomena that are accompanied by a decrease in volume are enhanced by pressure, and vice-versa (principle of Le Chatelier). Thus, under pressure, reaction equilibriums are shifted towards the most compact state, and the reaction rate constant is increased or decreased, depending on whether the “activation volume” of the reaction (i.e. volume of the activation complex less volume of reactants) is negative or positive. It is likely that pressure a\lso inhibits the availability of the activation energy required for some reactions, by affecting some other energy releasing enzymatic reactions (Farr, 1990). The compression energy of 1 litre of water at 400 MPa is 19.2 kJ, as compared to 20.9 kJ for heating 1 litre of water from 20 to 25C. The low energy levels involved in pressure processing may explain why covalent bonds of food constituents are usually less affected than weak interactions. Pressure can influence most biochemical reactions, since they often involve change in volume. High pressure controls certain enzymatic reactions. The effect of high pressure on protein/enzyme is reversible unlike temperature, in the range 100-400 MPa and is probably due to conformational changes and sub-unit dissociation and association process (Morild, 1981).
For both the pasteurization and sterilization processes, a combined treatment of high pressure and temperature are frequently considered to be most appropriate (Farr, 1990; Patterson, Quinn, Simpson, and Gilmour, 1995). Vegetative cells, including yeast and moulds, are pressure sensitive, i.e. they can be inactivated by pressures of ~300-600 MPa (Knorr, 1995; Patterson, Quinn, Simpson, and Gilmour, 1995). At high pressures, microbial death is considered to be due to permeabilization of cell membrane. For instance, it was observed that in the case of Saccharomyces cerevasia, at pressures of about 400 MPa, the structure and cytoplasmic organelles were grossly deformed and large quantities of intracellular material leaked out, while at 500 MPa, the nucleus could no longer be recognized, and a loss of intracellular material was almost complete (Farr, 1990). Changes that are induced in the cell morphology of the microorganisms are reversible at low pressures, but irreversible at higher pressures where microbial death occurs due to permeabilization of the cell membrane. An increase in process temperature above ambient temperature, and to a lesser extent, a decrease below ambient temperature, increases the inactivation rates of microorganisms during high pressure processing. Temperatures in the range 45 to 50C appear to increase the rate of inactivation of pathogens and spoilage microorganisms. Preservation of acid foods (pH ≤ 4.6) is, therefore, the most obvious application of HPP as such. Moreover, pasteurization can be performed even under chilled conditions for heat sensitive products. Low temperature processing can help to retain nutritional quality and functionality of raw materials treated and could allow maintenance of low temperature during post harvest treatment, processing, storage, transportation, and distribution periods of the life cycle of the food system (Knorr, 1995).
Bacterial spores are highly pressure resistant, since pressures exceeding 1200 MPa may be needed for their inactivation (Knorr, 1995). The initiation of germination or inhibition of germinated bacterial spores and inactivation of piezo-resistive microorganisms can be achieved in combination with moderate heating or other pretreatments such as ultrasound. Process temperature in the range 90-121C in conjunction with pressures of 500-800 MPa have been used to inactivate spores forming bacteria such as Clostridium botulinum. Thus, sterilization of low-acid foods (pH > 4.6), will most probably rely on a combination of high pressure and other forms of relatively mild treatments.
High-pressure application leads to the effective reduction of the activity of food quality related enzymes (oxidases), which ensures high quality and shelf stable products. Sometimes, food constituents offer piezo-resistance to enzymes. Further, high pressure affects only non-covalent bonds (hydrogen, ionic, and hydrophobic bonds), causes unfolding of protein chains, and has little effect on chemical constituents associated with desirable food qualities such as flavor, color, or nutritional content. Thus, in contrast to thermal processing, the application of high-pressure causes negligible impairment of nutritional values, taste, color flavor, or vitamin content (Hayashi, 1990). Small molecules such as amino acids, vitamins, and flavor compounds remain unaffected by high pressure, while the structure of the large molecules such as proteins, enzymes, polysaccharides, and nucleic acid may be altered (Balci and Wilbey, 1999).
High pressure reduces the rate of browning reaction (Maillard reaction). It consists of two reactions, condensation reaction of amino compounds with carbonyl compounds, and successive browning reactions including metanoidin formation and polymerization processes. The condensation reaction shows no acceleration by high pressure (5-50 MPa at 50C), because it suppresses the generation of stable free radicals derived from melanoidin, which are responsible for the browning reaction (Tamaoka, Itoh, and Hayashi, 1991). Gels induced by high pressure are found to be more glossy and transparent because of rearrangement of water molecules surrounding amino acid residues in a denatured state (Okamoto, Kawamura, and Hayashi, 1990).
The capability and limitations of HPP have been extensively reviewed (Thakur and Nelson, 1998; Smelt, 1998;Cheftal, 1995; Knorr, 1995; Fair, 1990; Tiwari, Jayas, and Holley, 1999; Cheftel, Levy, and Dumay, 2000; Messens, Van Camp, and Huyghebaert, 1997; Ontero and Sanz, 2000; Hugas, Garriga, and Monfort, 2002; Lakshmanan, Piggott,and Paterson, 2003; Balasubramaniam, 2003; Matser, Krebbers, Berg, and Bartels, 2004; Hogan, Kelly, and Sun, 2005; Mor-Mur and Yuste, 2005). Many of the early reviews primarily focused on the microbial efficacy of high-pressure processing. This review comprehensively covers the different types of products processed by highpressure technology alone or in combination with the other processes. It also discusses the effect of high pressure on food constituents such as enzymes and proteins. The applications of this technology in fruits and vegetable, dairy and animal product processing industries are covered. The effects of combining high- pressure treatment with other processing methods such as gamma- irradiation, alternating current, ultrasound, carbon dioxide, and anti microbial peptides have also been described. Special emphasis has been given to opportunities and challenges in high pressure processing of foods, which can potentially be explored and exploited.
EFFECT OF HIGH PRESSURE ON ENZYMES AND PROTEINS
Enzymes are a special class of proteins in which biological activity arises from active sites, brought together by a three- dimensional configuration of molecule. The changes in active site or protein denaturation can lead to loss of activity, or changes the functionality of the enzymes (Tsou, 1986). In addition to conformational changes, enzyme activity can be influenced by pressure-induced decompartmentalization (Butz, Koller, Tauscher, and Wolf, 1994; Gomes and Ledward, 1996). Pressure induced damage of membranes facilitates enzymesubstrate contact. The resulting reaction can either be accelerated or retarded by pressure (Butz, Koller, Tauscher, and Wolf, 1994; Gomes and Ledward, 1996; Morild, 1981). Hendrickx, Ludikhuy ze, Broeck, and Weemaes ( 1998) and Ludikhuyze, Van Loey, and Indrawati et al. (2003) reviewed the combined effect of pressure and temperature on enzymes related to the ity of fruits and vegetables, which comprises of kinetic information as well as process engineering aspects.
Pectin methylesterase (PME) is an enzyme, which normally tends to lower the viscosity of fruits products and adversely affect their texture. Hence, its inactivation is a prerequisite for the preservation of such products. Commercially, fruit products containing PME (e.g. orange juice and tomato products) are heat pasteurized to inactivate PME and prolong shelf life. However, heating can deteriorate the sensory and nutritional quality of the products. Basak and Ramaswamy (1996) showed that the inactivation of PME in orange juice was dependent on pressure level, pressure-hold time, pH, and total soluble solids. An instantaneous pressure kill was dependent only on pressure level and a secondary inactivation effect dependent on holding time at each pressure level. Nienaber and Shellhammer (2001) studied the kinetics of PME inactivation in orange juice over a range of pressures (400-600 MPa) and temperatures (25-5O0C) for various process holding times. PME inactivation followed a firstorder kinetic model, with a residual activity of pressure-resistant enzyme. Calculated D-values ranged from 4.6 to 117.5 min at 600 MPa/50C and 400 MPa/25C, respectively. Pressures in excess of 500 MPa resulted in sufficiently faster inactivation rates for economic viability of the process. Binh, Van Loey, Fachin, Verlent, Indrawati, and Hendrickx (2002a, 2002b) studied the kinetics of inactivation of strawberry PME. The combined effect of pressure and temperature on inactivation kinetics followed a fractional-conversion model. Purified strawberry PME was more stable toward high-pressure treatments than PME from oranges and bananas. Ly-Nguyen, Van Loey, Fachin, Verlent, Hendrickx (2002) showed that the inactivation of the banana PME enzyme during heating at temperature between 65 and 72.5C followed first order kinetics and the effect of pressure treatment of 600-700 MPa at 10C could be described using a fractionalconversion model. Stoforos, Crelier, Robert, and Taoukis (2002) demonstrated that under ambient pressure, tomato PME inactivation rates increased with temperature, and the highest rate was obtained at 75C. The inactivation rates were dramatically reduced as soon as the essing pressure was raised beyond 75C. High inactivation rates were obtained at a pressure higher than 700 MPa. Riahi and Ramaswamy (2003) studied high- pressure inactivation kinetics of PME isolated from a variety of sources and showed that PME from a microbial source was more resistant \to pressure inactivation than from orange peel. Almost a full decimal reduction in activity of commercial PME was achieved at 400 MPa within 20 min.
Verlent, Van Loey, Smout, Duvetter, Nguyen, and Hendrickx (2004) indicated that the optimal temperature for tomato pectinmethylesterase was shifted to higher values at elevated pressure compared to atmospheric pressure, creating the possibilities for rheology improvements by the application of high pressure.
Castro, Van Loey, Saraiva, Smout, and Hendrickx (2006) accurately described the inactivation of the labile fraction under mild-heat and high-pressure conditions by a fractional conversion model, while a biphasic model was used to estimate the inactivation rate constant of both the fractions at more drastic conditions of temperature/ pressure (10-64C, 0.1-800 MPa). At pressures lower than 300 MPa and temperatures higher than 54C, an antagonistic effect of pressure and temperature was observed.
Balogh, Smout, Binh, Van Loey, and Hendrickx (2004) observed the inactivation kinetics of carrot PME to follow first order kinetics over a range of pressure and temperature (650800 MPa, 10-40C). Enzyme stability under heat and pressure was reported to be lower in carrot juice and purified PME preparations than in carrots.
The presence of pectinesterase (PE) reduces the quality of citrus juices by destabilization of clouds. Generally, the inactivation of the enzyme is accomplished by heat, resulting in a loss of fresh fruit flavor in the juice. High pressure processing can be used to bypass the use of extreme heat for the processing of fruit juices. Goodner, Braddock, and Parish (1998) showed that the higher pressures (>600 MPa) caused instantaneous inactivation of the heat labile form of the enzyme but did not inactivate the heat stable form of PE in case of orange and grapefruit juices. PE activity was totally lost in orange juice, whereas complete inactivation was not possible in case of grapefruit juices. Orange juice pressurized at 700 MPa for l min had no cloud loss for more than 50 days. Broeck, Ludikhuyze, Van Loey, and Hendrickx (2000) studied the combined pressure-temperature inactivation of the labile fraction of orange PE over a range of pressure (0.1 to 900 MPa) and temperature (15 to 65C). Pressure and temperature dependence of the inactivation rate constants of the labile fraction was quantified using the well- known Eyring and Arrhenius relations. The stable fraction was inactivated at a temperature higher than 75C. Acidification (pH 3.7) enhanced the thermal inactivation of the stable fraction, whereas the addition of Ca^sup ++^ ions (IM) suppressed inactivation. At elevated pressure (up to 900 MPa), an antagonistic effect of pressure and temperature on inactivation of the stable fraction was observed. Ly-Nguyen, Van Loey, Smout, Ozean, Fachin, Verlent, Vu- Truong, Duvetter, and Hendrickx (2003) investigated the combined heat and pressure treatments on the inactivation of purified carrot PE, which followed a fractional-conversion model. The thermally stable fraction of the enzyme could not be inactivated. At a lower pressure (<300 MPa) and higher temperature (>50C), an antagonistic effect of pressure and heat was observed.
High pressures induced conformational changes in polygalacturonase (PG) causing reduced substrate binding affinity and enzyme inactivation. Eun, Seok, and Wan ( 1999) studied the effect of high-pressure treatment on PG from Chinese cabbage to prevent the softening and spoilage of plant-based foods such as kimchies without compromising quality. PG was inactivated by the application of pressure higher than 200 MPa for l min. Fachin, Van Loey, Indrawati, Ludikhuyze, and Hendrickx (2002) investigated the stability of tomato PG at different temperatures and pressures. The combined pressure temperature inactivation (300-600 MPa/50 -50C) of tomato PG was described by a fractional conversion model, which points to Ist-order inactivation kinetics of a pressure-sensitive enzyme fraction and to the occurrence of a pressure-stable PG fraction. Fachin, Smout, Verlent, Binh, Van Loey, and Hendrickx (2004) indicated that in the combination of pressure-temperature (5- 55C/100-600 MPa), the inactivation of the heat labile portion of purified tomato PG followed first order kinetics. The heat stable fraction of the enzyme showed pressure stability very similar to that of heat labile portion.
Peelers, Fachin, Smout, Van Loey, and Hendrickx (2004) demonstrated that effect of high-pressure was identical on heat stable and heat labile fractions of tomato PG. The isoenzyme of PG was detected in thermally treated (140C for 5 min) tomato pieces and tomato juice, whereas, no PG was found in pressure treated tomato juice or pieces.
Verlent, Van Loey, Smout, Duvetter, and Hendrickx (2004) investigated the effect of nigh pressure (0.1 and 500 MPa) and temperature (25-80C) on purified tomato PG. At atmospheric pressure, the optimum temperature for enzyme was found to be 55-60C and it decreased with an increase in pressure. The enzyme activity was reported to decrease with an increase in pressure at a constant temperature.
Shook, Shellhammer, and Schwartz (2001) studied the ability of high pressure to inactivate lipoxygenase, PE and PG in diced tomatoes. Processing conditions used were 400,600, and 800 MPa for 1, 3, and 5 min at 25 and 45C. The magnitude of the applied pressure had a significant effect in inactivating lipoxygenase and PG, with complete loss of activity occurring at 800 MPa. PE was very resistant to the pressure treatment.
Polyphenoloxidase and Pemxidase
Polyphenoloxidase (PPO) and peroxidase (POD), the enzymes responsible for color and flavor loss, can be selectively inactivated by a combined treatment of pressure and temperature. Gomes and Ledward (1996) studied the effects of pressure treatment (100-800 MPa for 1-20 min) on commercial PPO enzyme available from mushrooms, potatoes, and apples. Castellari, Matricardi, Arfelli, Rovere, and Amati ( 1997) demonstrated that there was a limited inactivation of grape PPO using pressures between 300 and 600 MPa. At 900 MPa, a low level of PPO activity was apparent. In order to reach complete inactivation, it may be necessary to use high- pressure processing treatments in conjunction with a mild thermal treatment (40-50C). Weemaes, Ludikhuyze, Broeck, and Hendrickx (1998) studied the pressure stabilities of PPO from apple, avocados, grapes, pears, and plums at pH 6-7. These PPO differed in pressure stability. Inactivation of PPO from apple, grape, avocado, and pear at room temperature (25C) became noticeable at approximately 600, 700, 800 and 900 MPa, respectively, and followed first-order kinetics. Plum PPO was not inactivated at room temperature by pressures up to 900 MPa. Rastogi, Eshtiaghi, and Knorr (1999) studied the inactivation effects of high hydrostatic pressure treatment (100-600 MPa) combined with heat treatment (0-60C) on POD and PPO enzyme, in order to develop high pressure-processed red grape juice having stable shelf-life. The studies showed that the lowest POD (55.75%) and PPO (41.86%) activities were found at 60C, with pressure at 600 and 100 MPa, respectively. MacDonald and Schaschke (2000) showed that for PPO, both temperature and pressure individually appeared to have similar effects, whereas the holding time was not significant. On the other hand, in case of POD, temperature as well as interaction between temperature and holding time had the greatest effect on activity. Namkyu, Seunghwan, and Kyung (2002) showed that mushroom PPO was highly pressure stable. Exposure to 600 MPa for 10 min reduced PPO activity by 7%; further exposure had no denaturing effect. Compression for 10 and 20 min up to 800 MPa, reduced activity by 28 and 43%, respectively.
Rapeanu, Van Loey, Smout, and Hendrickx (2005) indicated that the thermal and/or high-pressure inactivation of grape PPO followed first order kinetics. A third degree polynomial described the temperature/pressure dependence of the inactivation rate constants. Pressure and temperature were reported to act synergistically, except in the high temperature (≥45C)-low pressure (≥300 MPa) region where an antagonistic effect was observed.
Gomes, Sumner, and Ledward (1997) showed that the application of increasing pressures led to a gradual reduction in papain enzyme activity. A decrease in activity of 39% was observed when the enzyme solution was initially activated with phosphate buffer (pH 6.8) and subjected to 800 MPa at ambient temperature for 10 min, while 13% of the original activity remained when the enzyme solution was treated at 800 MPa at 60C for 10 min. In Tris buffer at pH 6.8 after treatment at 800 MPa and 20C, papain activity loss was approximately 24%. The inactivation of the enzyme is because of induced change at the active site causing loss of activity without major conformational changes. This loss of activity was due to oxidation of the thiolate ion present at the active site.
Weemaes, Cordt, Goossens, Ludikhuyze, Hendrickx, Heremans, and Tobback (1996) studied the effects of pressure and temperature on activity of 3 different alpha-amylases from Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus licheniformis. The changes in conformation of Bacillus licheniformis, Bacillus subtilis, and Bacillus amyloliquefaciens amylases occurred at pressures of 110, 75, and 65 MPa, respectively. Bacillus licheniformis amylase was more stable than amylases from Bacillus subtilis and Bacillus amyloliquefaciens to the combined heat/pressure treatment.
Riahi and Ramaswamy (2004) demonstrated that pressure inactivation of amylase in apple juice was significantly (P < 0.01 ) influenced by pH, pressure, holding time, and temperature. The inactivation was described using a bi-phasic model. The application of high pressure was sh\own to completely inactivate amylase. The importance of the pressure pulse and pressure hold approach for inactivation of amylase was also demonstrated.
High pressure denatures protein depending on the protein type, processing conditions, and the applied pressure. During the process of denaturation, the proteins may dissolve or precipitate on the application of high pressure. These changes are generally reversible in the pressure range 100-300 MPa and irreversible for the pressures higher than 300 MPa. Denaturation may be due to the destruction of hydrophobic and ion pair bonds, and unfolding of molecules. At higher pressure, oligomeric proteins tend to dissociate into subunits becoming vulnerable to proteolysis. Monomeric proteins do not show any changes in proteolysis with increase in pressure (Thakur and Nelson, 1998).
High-pressure effects on proteins are related to the rupture on non-covalent interactions within protein molecules, and to the subsequent reformation of intra and inter molecular bonds within or between the molecules. Different types of interactions contribute to the secondary, tertiary, and quaternary structure of proteins. The quaternary structure is mainly held by hydrophobic interactions that are very sensitive to pressure. Significant changes in the tertiary structure are observed beyond 200 MPa. However, a reversible unfolding of small proteins such as ribonuclease A occurs at higher pressures (400 to 800 MPa), showing that the volume and compressibility changes during denaturation are not completely dominated by the hydrophobic effect. Denaturation is a complex process involving intermediate forms leading to multiple denatured products. secondary structure changes take place at a very high pressure above 700 MPa, leading to irreversible denaturation (Balny and Masson, 1993).
Figure 1 General scheme for pressure-temperature phase diagram of proteins, (from Messens, Van Camp, and Huyghebaert, 1997).
When the pressure increases to about 100 MPa, the denaturation temperature of the protein increases, whereas at higher pressures, the temperature of denaturation usually decreases. This results in the elliptical phase diagram of native denatured protein shown in Fig. 1. A practical consequence is that under elevated pressures, proteins denature usually at room temperature than at higher temperatures. The phase diagram also specifies the pressure- temperature range in which the protein maintains its native structure. Zone III specifies that at high temperatures, a rise in denaturation temperature is found with increasing pressure. Zone II indicates that below the maximum transition temperature, protein denaturation occurs at the lower temperatures under higher pressures. Zone III shows that below the temperature corresponding to the maximum transition pressure, protein denaturation occurs at lower pressures using lower temperatures (Messens, Van Camp, and Huyghebaert, 1997).
The application of high pressure has been shown to destabilize casein micelles in reconstituted skim milk and the size distribution of spherical casein micelles decrease from 200 to 120 nm; maximum changes have been reported to occur between 150-400 MPa at 20C. The pressure treatment results in reduced turbidity and increased lightness, which leads to the formation of a virtually transparent skim milk (Shibauchi, Yamamoto, and Sagara, 1992; Derobry, Richard, and Hardy, 1994). The gels produced from high-pressure treated skim milk showed improved rigidity and gel breaking strength (Johnston, Austin, and Murphy, 1992). Garcia, Olano, Ramos, and Lopez (2000) showed that the pressure treatment at 25C considerably reduced the micelle size, while pressurization at higher temperature progressively increased the micelle dimensions. Anema, Lowe, and Stockmann (2005) indicated that a small decrease in the size of casein micelles was observed at 100 MPa, with slightly greater effects at higher temperatures or longer pressure treatments. At pressure >400 MPa, the casein micelles disintegrated. The effect was more rapid at higher temperatures although the final size was similar in all samples regardless of the pressure or temperature. At 200 MPa and 1O0C, the casein micelle size decreased slightly on heating, whereas, at higher temperatures, the size increased as a result of aggregation. Huppertz, Fox, and Kelly (2004a) showed that the size of casein micelles increased by 30% upon high-pressure treatment of milk at 250 MPa and micelle size dropped by 50% at 400 or 600 MPa.
Huppertz, Fox, and Kelly (2004b) demonstrated that the high- pressure treatment of milk at 100-600 MPa resulted in considerable solubilization of alphas 1- and beta-casein, which may be due to the solubilization of colloidal calcium phosphate and disruption of hydrophobic interactions. On storage of pressure, treated milk at 5C dissociation of casein was largely irreversible, but at 20C, considerable re-association of casein was observed. The hydration of the casein micelles increased on pressure treatment (100-600 MPa) due to induced interactions between caseins and whey proteins. Pressure treatment increased levels of alphas 1- and beta-casein in the soluble phase of milk and produced casein micelles with properties different to those in untreated milk. Huppertz, Fox, and Kelly (2004c) demonstrated that the casein micelle size was not influenced by pressures less than 200 MPa, but a pressure of 250 MPa increased the micelle size by 25%, while pressures of 300 MPa or greater, irreversibly reduced the size to 50% ofthat in untreated milk. Denaturation of alpha-lactalbumin did not occur at pressures less than or equal to 400 MPa, whereas beta-lactoglobulin was denatured at pressures greater than 100 MPa.
Galazka, Ledward, Sumner, and Dickinson (1997) reported loss of surface hydrophobicity due to application of 300 MPa in dilute solution. Pressurizing beta-lactoglobulin at 450 MPa for 15 minutes resulted in reduced solubility in water. High-pressure treatment induced extensive protein unfolding and aggregation when BSA was pressurized at 400 MPa. Beta-lactoglobulin appears to be more sensitive to pressure than alpha-lactalbumin. Olsen, Ipsen, Otte, and Skibsted (1999) monitored the state of aggregation and thermal gelation properties of pressure-treated beta-lactoglobulin immediately after depressurization and after storage for 24 h at 50C. A pressure of 150 MPa applied for 30 min, or pressures higher than 300 MPa applied for 0 or 30 min, led to formation of soluble aggregates. When continued for 30 min, a pressure of 450 MPa caused gelation of the 5% beta-lactoglobulin solution. Iametti, Tansidico, Bonomi, Vecchio, Pittia, Rovere, and DaIl’Aglio (1997) studied irreversible modifications in the tertiary structure, surface hydrophobicity, and association state of beta-lactoglobulin, when solutions of the protein at neutral pH and at different concentrations, were exposed to pressure. Only minor irreversible structural modifications were evident even for treatments as intense as 15 min at 900 MPa. The occurrence of irreversible modifications was time-dependent at 600 MPa but was complete within 2 min at 900 MPa. The irreversibly modified protein was soluble, but some covalent aggregates were formed. Subirade, Loupil, Allain, and Paquin (1998) showed the effect of dynamic high pressure on the secondary structure of betalactoglobulin. Thermal and pH sensitivity of pressure treated beta-lactoglobulin was different, suggesting that the two forms were stabilized by different electrostatic interactions. Walker, Farkas, Anderson, and Goddik (2004) used high- pressure processing (510 MPa for 10 min at 8 or 24C) to induce unfolding of beta-lactoglobulin and characterized the protein structure and surface-active properties. The secondary structure of the protein processed at 8C appeared to be unchanged, whereas at 24C alpha-helix structure was lost. Tertiary structures changed due to processing at either temperature. Model solutions containing the pressure-treated beta-lactoglobulin showed a significant decrease in surface tension. Izquierdo, Alli, Gmez, Ramaswamy, and Yaylayan (2005) demonstrated that under high-pressure treatments (100-300 MPa), the β-lactoglobulin AB was completely hydrolyzed by pronase and α-chymotrypsin. Hinrichs and Rademacher (2005) showed that the denaturation kinetics of beta-lactoglobulin followed second order kinetics while for alpha-lactalbumin it was 2.5. Alpha- lactalbumin was more resistant to denaturation than beta- lactoglobulin. The activation volume for denaturation of beta- lactoglobulin was reported to decrease with increasing temperature, and the activation energy increased with pressure up to 200 MPa, beyond which it decreased. This demonstrated the unfolding of the protein molecules.
Drake, Harison, Apslund, Barbosa-Canovas, and Swanson (1997) demonstrated that the percentage moisture and wet weight yield of cheese from pressure treated milk were higher than pasteurized or raw milk cheese. The microbial quality was comparable and some textural defects were reported due to the excess moisture content. Arias, Lopez, and Olano (2000) showed that high-pressure treatment at 200 MPa significantly reduced rennet coagulation times over control samples. Pressurization at 400 MPa led to coagulation times similar to those of control, except for milk treated at pH 7.0, with or without readjustment of pH to 6.7, which presented significantly longer coagulation times than their non-pressure treated counterparts.
Hinrichs and Rademacher (2004) demonstrated that the isobaric (200-800 MPa) and isothermal (-2 to 70C) denaturation of beta- lactoglobulin and alpha-lactalbumin of whey protein followed 3rd and 2nd order kinetics, respectively. Isothermal pressure denaturation of both beta-lactoglobulin A and B did not differ significantly and an increase in temperature resulted in an increase in thedenaturation rate. At pressures higher than 200 MPa, the denaturation rate was limited by the aggregation rate, while the pressure resulted in the unfolding of molecules. The kinetic parameters of denaturation were estimated using a single step non- linear regression method, which allowed a global fit of the entire data set. Huppertz, Fox, and Kelly (2004d) examined the high- pressure induced denaturation of alpha-lactalbumin and beta- lactoglobulin in dairy systems. The higher level of pressure- induced denaturation of both proteins in milk as compared to whey was due to the absence of casein micelles and colloidal calcium phosphate in the whey.
The conformation of BSA was reported to remain fairly stable at 400 MPa due to a high number of disulfide bonds which are known to stabilize its three dimensional structure (Hayakawa, Kajihara, Morikawa, Oda, and Fujio, 1992). Kieffer and Wieser (2004) indicated that the extension resistance and extensibility of wet gluten were markedly influenced by high pressure (up to 800 MPa), while the temperature and the duration of pressure treatment (30-80C for 2-20 min) had a relatively lesser effect. The application of high pressure resulted in a marked decrease in protein extractability due to the restructuring of disulfide bonds under high pressure leading to the incorporation of alpha- and gamma-gliadins in the glutenin aggregate. The change in secondary structure following high- pressure treatment was also reported.
The pressure treatment of myosin led to head-to-head interaction to form oligomers (clumps), which became more compact and larger in size during storage at constant pressure. Even after pressure treatment at 210 MPa for 5 minutes, monomieric myosin molecules increased and no gelation was observed for pressure treatment up to 210 MPa for 30 minutes. Pressure treatment did not also affect the original helical structure of the tail in the myosin monomers. Angsupanich, Edde, and Ledward (1999) showed that high pressure- induced denaturation of myosin led to formation of structures that contained hydrogen bonds and were additionally stabilized by disulphide bonds.
Application of 750 MPa for 20 minutes resulted in dimerization of metmyoglobin in the pH range of 6-10, whereas maximum pH was not at isoelectric pH (6.9). Under acidic pH conditions, no dimers were formed (Defaye and Ledward, 1995). Zipp and Kouzmann ( 1973) showed the formation of precipitate when pressurized (750 MPa for 20 minutes) near the isoelectric point, the precipitate redissolved slowly during storage. Pressure treatment had no effect on lipid oxidation in the case of minced meat packed in air at pressure less than 300 MPa, while the oxidation increased proportionally at higher pressures. However, on exposure to higher pressure, minced meat in contact with air oxidized rapidly. Pressures > 300-400 MPa caused marked denaturation of both myofibriller and sarcoplasmic proteins in washed pork muscle and pork mince (Ananth, Murano and Dickson, 1995). Chapleau and Lamballerie (2003) showed that high-pressure treatment induced a threefold increase in the surface hydrophobicity of myofibrillar proteins between O and 450 MPa. Chapleau, Mangavel, Compoint, and Lamballerie (2004) reported that high pressure modified the secondary structure of myofibrillar proteins extracted from cattle carcasses. Irreversible changes and aggregation were reported at a pressure higher than 300 MPa, which can potentially affect the functional properties of meat products. Lamballerie, Perron, Jung, and Cheret (2003) indicated that high pressure treatment increases cathepsin D activity, and that pressurized myofibrils are more susceptible to cathepsin D action than non- pressurized myofibrils. The highest cathepsin D activity was observed at 300 MPa. Cariez, Veciana, and Cheftel ( 1995) demonstrated that L color values increased significantly in meat treated at 200-350 MPa, the meat becoming pink, and a-value decreased in meat treated at 400-500 MPa to give a grey-brown color. The total extractable myoglobin decreased in meat treated at 200- 500 MPa, while the metmyoglobin content of meat increased and the oxymyoglobin decreased at 400500 MPa. Meat discoloration from pressure processing resulted in a whitening effect at 200-300 MPa due to globin denaturation, and/or haem displacement/release, or oxidation of ferrous myoglobin to ferric myoglobin at pressure higher than 400 MPa.
The conformation of the main protein component of egg white, ovalbumin, remains fairly stable when pressurized at 400 MPa, may be due to the four disulfide bonds and non-covalent interactions stabilizing the three dimensional structure of ovalbumin (Hayakawa, Kajihara, Morikawa, Oda, and Fujio, 1992). Hayashi, Kawamura, Nakasa and Okinada (1989) reported irreversible denaturation of egg albumin at 500-900 MPa with concomitant increase in susceptibility to subtilisin. Zhang, Li, and Tatsumi (2005) demonstrated that the pressure treatment (200-500 MPa) resulted in denaturation of ovalbumin. The surface hydrophobicity of ovalbumin was found to increase with increase in pressure treatment and the presence of polysaccharide protected the protein against denaturation. Iametti, Donnizzelli, Pittia, Rovere, Squarcina, and Bonomi (1999) showed that the addition of NaCl or sucrose to egg albumin prior to high- pressure treatment (up to 10 min at 800 MPa) prevented insolubulization or gel formation after pressure treatment. As a consequence of protein unfolding, the treated albumin had increased viscosity but retained its foaming and heat-gelling properties. Farr (1990) reported the modification of functionality of egg proteins. Egg yolk formed a gel when subjected to a pressure of 400 MPa for 30 minutes at 25C, kept its original color, and was soft and adhesive. The hardness of the pressure treated gel increased and adhesiveness decreased with an increase in pressure. Plancken, Van Loey, and Hendrickx (2005) showed that the application of high pressure (400- 700 MPa) to egg white solution resulted in an increase in turbidity, surface hydrophobicity, exposed sulfhydryl content, and susceptibility to enzymatic hydrolysis, while it resulted in a decrease in protein solubility, total sulfhydryl content, denaturation enthalpy, and trypsin inhibitory activity. The pressure- induced changes in these properties were shown to be dependent on the pressuretemperature and the pH of the solution. Speroni, Puppo, Chapleau, Lamballerie, Castellani, Aon, and Anton (2005) indicated that the application of high pressure (200-600 MPa) at 2OC to low- density lipoproteins did not change the solubility even if the pH is changed, whereas aggregation and protein denaturation were drastically enhanced at pH 8. Further, the application of high- pressure under alkaline pH conditions resulted in decreased droplet flocculation of low-density lipoproteins dispersions.
The minimum pressure required for the inducing gelation of soya proteins was reported to be 300 MPa for 10-30 minutes and the gels formed were softer with lower elastic modulus in comparison with heat-treated gels (Okamoto, Kawamura, and Hayashi, 1990). The treatment of soya milk at 500 MPa for 30 min changed it from a liquid state to a solid state, whereas at lower pressures and at 500 MPa for 10 minutes, the milk remained in a liquid state, but indicated improved emulsifying activity and stability (Kajiyama, Isobe, Uemura, and Noguchi, 1995). The hardness of tofu gels produced by high-pressure treatment at 300 MPa for 10 minutes was comparable to heat induced gels. Puppo, Chapleau, Speroni, Lamballerie, Michel, Anon, and Anton (2004) demonstrated that the application of high pressure (200-600 MPa) on soya protein isolate at pH 8.0 resulted in an increase in a protein hydorphobicity and aggregation, a reduction of free sulfhydryl content and a partial unfolding of the 7S and 11S fractions at pH 8. The change in the secondary structure leading to a more disordered structure was also reported. Whereas at pH 3.0, the protein was partially denatured and insoluble aggregates were formed, the major molecular unfolding resulted in decreased thermal stability, increased protein solubility, and hydorphobicity. Puppo, Speroni, Chapleau, Lamballerie, An, and Anton (2005) studied the effect of high- pressure (200, 400, and 600 MPa for 10 min at 10C) on the emulsifying properties of soybean protein isolates at pH 3 and 8 (e.g. oil droplet size, flocculation, interfacial protein concentration, and composition). The application of pressure higher than 200 MPa at pH 8 resulted in a smaller droplet size and an increase in the levels of depletion flocculation. However, a similar effect was not observed at pH 3. Due to the application of high pressure, bridging flocculation decreased and the percentage of adsorbed proteins increased irrespective of the pH conditions. Moreover, the ability of the protein to be adsorbed at the oil- water interface increased. Zhang, Li, Tatsumi, and Isobe (2005) showed that the application of high pressure treatment resulted in the formation of more hydrophobic regions in soy protein, which dissociated into subunits, which in some cases formed insoluble aggregates. High-pressure denaturation of beta-conglycinin (7S) and glycinin (11S) occurred at 300 and 400 MPa, respectively. The gels formed had the desirable strength and a cross-linked network microstructure.
Soybean whey is a by-product of tofu manufacture. It is a good source of peptides, proteins, oligosaccharides, and isoflavones, and can be used in special foods for the elderly persons, athletes, etc. Prestamo and Penas (2004) studied the antioxidative activity of soybean whey proteins and their pepsin and chymotrypsin hydrolysates. The chymotrypsin hydrolysate showed a higher antioxidative activity than the non-hydrolyzed protein, but the pepsin hydrolysate showed an opposite trend. High pressure processing at 100 MPa inc\reased the antioxidative activity of soy whey protein, but decreased the antioxidative activity of the hydrolysates. High pressure processing increased the pH of the protein hydrolysates. Penas, Prestamo, and Gomez (2004) demonstrated that the application of high pressure (100 and 200 MPa, 15 min, 37C) facilitated the hydrolysis of soya whey protein by pepsin, trypsin, and chymotrypsin. It was shown that the highest level of hydrolysis occurred at a treatment pressure of 100 MPa. After the hydrolysis, 5 peptides under 14 kDa with trypsin and chymotrypsin, and 11 peptides with pepsin were reported.
COMBINATION OF HIGHPRESSURE TREATMENT WITH OTHER NON-THERMAL PROCESSING METHODS
Many researchers have combined the use of high pressure with other non-thermal operations in order to explore the possibility of synergy between processes. Such attempts are reviewed in this section.
Crawford, Murano, Olson, and Shenoy (1996) studied the combined effect of high pressure and gamma-irradiation for inactivating Clostridium spmgenes spores in chicken breast. Application of high pressure reduced the radiation dose required to produce chicken meat with extended shelf life. The application of high pressure (600 MPa for 20 min at 8O0C) reduced the irradiation doses required for one log reduction of Clostridium spmgenes from 4.2 kGy to 2.0 kGy. Mainville, Montpetit, Durand, and Farnworth (2001) studied the combined effect of irradiation and high pressure on microflora and microorganisms of kefir. The irradiation treatment of kefir at 5 kGy and high-pressure treatment (400 MPa for 5 or 30 min) deactivated the bacteria and yeast in kefir, while leaving the proteins and lipids unchanged.
The exposure of microbial cells and spores to an alternating current (50 Hz) resulted in the release of intracellular materials causing loss or denaturation of cellular components responsible for the normal functioning of the cell. The lethal damage to the microorganisms enhanced when the organisms are exposed to an alternating current before and after the pressure treatment. High- pressure treatment at 300 MPa for 10 min for Escherichia coli cells and 400 MPa for 30 min for Bacillus subtalis spores, after the alternating current treatment, resulted in reduced surviving fractions of both the organisms. The combined effect was also shown to reduce the tolerant level of microorganisms to other challenges (Shimada and Shimahara, 1985, 1987; Shimada, 1992).
The pretreatment with ultrasonic waves (100 W/cm^sup 2^ for 25 min at 25C) followed by high pressure (400 MPa for 25 min at 15C) was shown to result in complete inactivation of Rhodoturola rubra. Neither ultrasonic nor high-pressure treatment alone was found to be effective (Knorr, 1995).
Carbon Dioxide and Argon
Heinz and Knorr (1995) reported a 3 log reduction of supercritical CO2 pretreated cultures. The effect of the pretreatment on germination of Bacillus subtilis endospores was monitored. The combination of high pressure and mild heat treatment was the most effective in reducing germination (95% reduction), but no spore inactivation was observed.
Park, Lee, and Park (2002) studied the combination of high- pressure carbon dioxide and high pressure as a nonthermal processing technique to enhance the safety and shelf life of carrot juice. The combined treatment of carbon dioxide (4.90 MPa) and high-pressure treatment (300 MPa) resulted in complete destruction of aerobes. The increase in high pressure to 600 MPa in the presence of carbon dioxide resulted in reduced activities of polyphenoloxidase (11.3%), lipoxygenase (8.8%), and pectin methylesterase (35.1%). Corwin and Shellhammer (2002) studied the combined effect of high-pressure treatment and CO2 on the inactivation of pectinmethylesterase, polyphenoloxidase, Lactobacillus plantarum, and Escherichia coli. An interaction was found between CO2 and pressure at 25 and 50C for pectinmethylesterase and polyphenoloxidase, respectively. The activity of polyphenoloxidase was decreased by CO2 at all pressure treatments. The interaction between CO2 and pressure was significant for Lactobacillus plantarum, with a significant decrease in survivors due to the addition of CO2 at all pressures studied. No significant effect on E. coli survivors was seen with CO2 addition. Truong, Boff, Min, and Shellhammer (2002) demonstrated that the addition of CO2 (0.18 MPa) during high pressure processing (600 MPa, 25C) of fresh orange juice increases the rate of PME inactivation in Valencia orange juice. The treatment time due to CO2 for achieving the equivalent reduction in PME activity was from 346 s to 111 s, but the overall degree of PME inactivation remained unaltered.
Fujii, Ohtani, Watanabe, Ohgoshi, Fujii, and Honma (2002) studied the high-pressure inactivation of Bacillus cereus spores in water containing argon. At the pressure of 600 MPa, the addition of argon reportedly accelerated the inactivation of spores at 20C, but had no effect on the inactivation at 40C.
The complex physicochemical environment of milk exerted a strong protective effect on Escherichia coli against high hydrostatic pressure inactivation, reducing inactivation from 7 logs at 400 MPa to only 3 logs at 700 MPa in 15 min at 20C. A substantial improvement in inactivation efficiency at ambient temperature was achieved by the application of consecutive, short pressure treatments interrupted by brief decompressions. The combined effect of high pressure (500 MPa) and natural antimicrobial peptides (lysozyme, 400 g/ml and nisin, 400 g/ml) resulted in increased lethality for Escherichia coli in milk (Garcia, Masschalck, and Michiels, 1999).
OPPORTUNITIES FOR HIGH PRESSURE ASSISTED PROCESSING
The inclusion of high-pressure treatment as a processing step within certain manufacturing flow sheets can lead to novel products as well as new process development opportunities. For instance, high pressure can precede a number of process operations such as blanching, dehydration, rehydration, frying, and solid-liquid extraction. Alternatively, processes such as gelation, freezing, and thawing, can be carried out under high pressure. This section reports on the use of high pressures in the context of selected processing operations.
Eshtiaghi and Knorr (1993) employed high pressure around ambient temperatures to develop a blanching process similar to hot water or steam blanching, but without thermal degradation; this also minimized problems associated with water disposal. The application of pressure (400 MPa, 15 min, 20C) to the potato sample not only caused blanching but also resulted in a four-log cycle reduction in microbial count whilst retaining 85% of ascorbic acid. Complete inactivation of polyphenoloxidase was achieved under the above conditions when 0.5% citric acid solution was used as the blanching medium. The addition of 1 % CaCl^sub 2^ solution to the medium also improved the texture and the density. The leaching of potassium from the high-pressure treated sample was comparable with a 3 min hot water blanching treatment (Eshtiaghi and Knorr, 1993). Thus, high- pressures can be used as a non-thermal blanching method.
Dehydration and Osmotic Dehydration
The application of high hydrostatic pressure affects cell wall structure, leaving the cell more permeable, which leads to significant changes in the tissue architecture (Fair, 1990; Dornenburg and Knorr, 1994, Rastogi, Subramanian, and Raghavarao, 1994; Rastogi and Niranjan, 1998; Rastogi, Raghavarao, and Niranjan, 2005). Eshtiaghi, Stute, and Knorr (1994) reported that the application of pressure (600 MPa, 15 min at 70C) resulted in no significant increase in the drying rate during fluidized bed drying of green beans and carrot. However, the drying rate significantly increased in the case of potato. This may be due to relatively limited permeabilization of carrot and beans cells as compared to potato. The effects of chemical pre-treatment (NaOH and HCl treatment) on the rates of dehydration of paprika were compared with products pre-treated by applying high pressure or high intensity electric field pulses (Fig. 2). High-pressure (400 MPa for 10 min at 25C) and high intensity electric field pulses (2.4 kV/cm, pulse width 300 s, 10 pulses, pulse frequency 1 Hz) were found to result in drying rates comparable with chemical pre-treatments. The latter pre-treatments, however, eliminated the use of chemicals (Ade- Omowaye, Rastogi, Angersbach, and Knorr, 2001).
Figure 2 (a) Effects of various pre-treatments such as hot water blanching, high pressure and high intensity electric field pulse treatment on dehydration characteristics of red paprika (b) comparison of drying time (from Ade-Omowaye, Rastogi, Angersbach, and Knorr, 2001).
Figure 3 (a) Variation of moisture and (b) solid content (based on initial dry matter content) with time during osmotic dehydration (from Rastogi and Niranjan, 1998).
Generally, osmotic dehydration is a slow process. Application of high pressures causes permeabilization of the cell structure (Dornenburg and Knorr, 1993; Eshtiaghi, Stute, and Knorr, 1994; Fair, 1990; Rastogi, Subramanian, and Raghavarao, 1994). This phenomenon has been exploited by Rastogi and Niranjan (1998) to enhance mass transfer rates during the osmotic dehydration of pineapple (Ananas comsus). High-pressure pre-treatments (100-800 MPa) were found to enhance both water removal as well as solid gain (Fig. 3). Measured diffusivity values for water were found to be four-fold greater, whilst solute (sugar) diffusivity values were found to be two-fold greater. Compression and decompression occurring during high pressure pre-treatment itself caused the removal of a significant amount of water, which was attributed to the cell wall rupture (Rastogi and Niranjan, 1998). Differential interference contrast microscopic examination showed the ext\ent of cell wall break-up with applied pressure (Fig. 4). Sopanangkul, Ledward, and Niranjan (2002) demonstrated that the application of high pressure (100 to 400 MPa) could be used to accelerate mass transfer during ingredient infusion into foods. Application of pressure opened up the tissue structure and facilitated diffusion. However, higher pressures above 400 MPa induced starch gelatinization also and hindered diffusion. The values of the diffusion coefficient were dependent on cell permeabilization and starch gelatinization. The maximum value of diffusion coefficient observed represented an eight-fold increase over the values at ambient pressure.
The synergistic effect of cell permeabilization due to high pressure and osmotic stress as the dehydration proceeds was demonstrated more clearly in the case of potato (Rastogi, Angersbach, and Knorr, 2000a, 2000b, 2003). The moisture content was reduced and the solid content increased in the case of samples treated at 400 MPa. The distribution of relative moisture (M/M^sub o^) and solid (S/S^sub o^) content as well as the cell permeabilization index (Zp) (shown in Fig. 5) indicate that the rate of change of moisture and solid content was very high at the interface and decreased towards the center (Rastogi, Angersbach, and Knorr, 2000a, 2000b, 2003).
Most dehydrated foods are rehydrated before consumption. Loss of solids during rehydration is a major problem associated with the use of dehydrated foods. Rastogi, Angersbach, Niranjan, and Knorr (2000c) have studied the transient variation of moisture and solid content during rehydration of dried pineapples, which were subjected to high pressure treatment prior to a two-stage drying process consisting of osmotic dehydration and finish-drying at 25C (Fig. 6). The diffusion coefficients for water infusion as well as for solute diffusion were found to be significantly lower in high-pressure pre- treated samples. The observed decrease in water diffusion coefficient was attributed to the permeabilization of cell membranes, which reduces the rehydration capacity (Rastogi and Niranjan, 1998). The solid infusion coefficient was also lower, and so was the release of the cellular components, which form a gel- network with divalent ions binding to de-esterified pectin (Basak and Ramaswamy, 1998; Eshtiaghi, Stute, and Knorr, 1994; Rastogi Angersbach, Niranjan, and Knorr, 2000c). Eshtiaghi, Stute, and Knorr (1994) reported that high-pressure treatment in conjunction with subsequent freezing could improve mass transfer during rehydration of dried plant products and enhance product quality.
Figure 4 Microstructures of control and pressure treated pineapple (a) control; (b) 300 MPa; (c) 700 MPa. ( 1 cm = 41.83 m) (from Rastogi and Niranjan, 1998).
Ahromrit, Ledward, and Niranjan (2006) explored the use of high pressures (up to 600 MPa) to accelerate water uptake kinetics during soaking of glutinous rice. The results showed that the length and the diameter the of the rice were positively correlated with soaking time, pressure and temperature. The water uptake kinetics was shown to follow the well-known Fickian model. The overall rates of water uptake and the equilibrium moisture content were found to increase with pressure and temperature.
Zhang, Ishida, and Isobe (2004) studied the effect of highpressure treatment (300-500 MPa for 0-380 min at 20C) on the water uptake of soybeans and resulting changes in their microstructure. The NMR analysis indicated that water mobility in high-pressure soaked soybean was more restricted and its distribution was much more uniform than in controls. The SEM analysis revealed that high pressure changed the microstructures of the seed coat and hilum, which improved water absorption and disrupted the individual spherical protein body structures. Additionally, the DSC and SDS-PAGE analysis revealed that proteins were partially denatured during the high pressure soaking. Ibarz, Gonzalez, Barbosa-Canovas (2004) developed the kinetic models for water absorption and cooking time of chickpeas with and without prior high-pressure treatment (275-690 MPa). Soaking was carried out at 25C for up to 23 h and cooking was achieved by immersion in boiling water until they became tender. As the soaking time increased, the cooking time decreased. High-pressure treatment for 5 min led to reductions in cooking times equivalent to those achieved by soaking for 60-90 min.
Ramaswamy, Balasubramaniam, and Sastry (2005) studied the effects of high pressure (33, 400 and 700 MPa for 3 min at 24 and 55C) and irradiation (2 and 5 kGy) pre-treatments on hydration behavior of navy beans by soaking the treated beans in water at 24 and 55C. Treating beans under moderate pressure (33 MPa) resulted in a high initial moisture uptake (0.59 to 1.02 kg/kg dry mass) and a reduced loss of soluble materials. The final moisture content after three hours of soaking was the highest in irradiated beans (5 kGy) followed by high-pressure treatment (33 MPa, 3 min at 55C). Within the experimental range of the study, Peleg’s model was found to satisfactorily describe the rate of water absorption of navy beans.
A reduction of 40% in oil uptake during frying was observed, when thermally blanched frozen potatoes were replaced by high pressure blanched frozen potatoes. This may be due to a reduction in moisture content caused by compression and decompression (Rastogi and Niranjan, 1998), as well as the prevalence of different oil mass transfer mechanisms (Knorr, 1999).
Solid Liquid Extraction
The application of high pressure leads to rearrangement in tissue architecture, which results in increased extractability even at ambient temperature. Extraction of caffeine from coffee using water could be increased by the application of high pressure as well as increase in temperature (Knorr, 1999). The effect of high pressure and temperature on caffeine extraction was compared to extraction at 100C as well as atmospheric pressure (Fig. 7). The caffeine yield was found to increase with temperature at a given pressure. The combination of very high pressures and lower temperatures could become a viable alternative to current industrial practice.
Figure 5 Distribution of (a, b) relative moisture and (c, d) solid content as well as (e, f) cell disi
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Notes on the Bible, by Albert Barnes, , at sacred-texts.com
Now the word of the Lord - , literally, "And, ..." This is the way in which the several inspired writers of the Old Testament mark that what it was given them to write was united onto those sacred books which God had given to others to write, and it formed with them one continuous whole. The word, "And," implies this. It would do so in any language, and it does so in Hebrew as much as in any other. As neither we, nor any other people, would, without any meaning, use the word, And, so neither did the Hebrews. It joins the four first books of Moses together; it carries on the history through Joshua, Judges, the Books of Samuel and of the Kings. After the captivity, Ezra and Nehemiah begin again where the histories before left off; the break of the captivity is bridged over; and Ezra, going back in mind to the history of God's people before the captivity, resumes the history, as if it had been of yesterday, "And in the first year of Cyrus." It joins in the story of the Book of Ruth before the captivity, and that of Esther afterward. At times, even prophets employ it, in using the narrative form of themselves, as Ezekiel, "and it was in the thirtieth year, in the fourth month, in the fifth day of the month, and I was in the captivity by the river of Chebar, the heavens opened and I saw." If a prophet or historian wishes to detach his prophecy or his history, he does so; as Ezra probably began the Book of Chronicles anew from Adam, or as Daniel makes his prophecy a whole by itself. But then it is the more obvious that a Hebrew prophet or historian, when he does begin with the word, "And," has an object in so beginning; he uses an universal word of all languages in its uniform meaning in all language, to join things together.
And yet more precisely; this form, "and the word of the Lord came to - saying," occurs over and over again, stringing together the pearls of great price of God's revelations, and uniting this new revelation to all those which had preceded it. The word, "And," then joins on histories with histories, revelations with revelations, uniting in one the histories of God's works and words, and blending the books of Holy Scripture into one divine book.
But the form of words must have suggested to the Jews another thought, which is part of our thankfulness and of our being Act 11:18, "then to the Gentiles also hath God given repentance unto life." The words are the self-same familiar words with which some fresh revelation of God's will to His people had so often been announced. Now they are prefixed to God's message to the pagan, and so as to join on that message to all the other messages to Israel. Would then God deal thenceforth with the pagan as with the Jews? Would they have their prophets? Would they be included in the one family of God? The mission of Jonah in itself was an earnest that they would, for God. Who does nothing fitfully or capriciously, in that He had begun, gave an earnest that He would carry on what He had begun. And so thereafter, the great prophets, Isaiah, Jeremiah, Ezekiel, were prophets to the nations also; Daniel was a prophet among them, to them as well as to their captives.
But the mission of Jonah might, so far, have been something exceptional. The enrolling his book, as an integral part of the Scriptures, joining on that prophecy to the other prophecies to Israel, was an earnest that they were to be parts of one system. But then it would be significant also, that the records of God's prophecies to the Jews, all embodied the accounts of their impenitence. Here is inserted among them an account of God's revelation to the pagan, and their repentance. "So many prophets had been sent, so many miracles performed, so often had captivity been foreannounced to them for the multitude of their sins. and they never repented. Not for the reign of one king did they cease from the worship of the calves; not one of the kings of the ten tribes departed from the sins of Jeroboam? Elijah, sent in the Word and Spirit of the Lord, had done many miracles, yet obtained no abandonment of the calves. His miracles effected this only, that the people knew that Baal was no god, and cried out, "the Lord He is the God." Elisha his disciple followed him, who asked for a double portion of the Spirit of Elijah, that he might work more miracles, to bring back the people.
He died, and, after his death as before it, the worship of the calves continued in Israel. The Lord marveled and was weary of Israel, knowing that if He sent to the pagan they would bear, as he saith to Ezekiel. To make trial of this, Jonah was chosen, of whom it is recorded in the Book of Kings that he prophesied the restoration of the border of Israel. When then he begins by saying, "And the word of the Lord came to Jonah," prefixing the word "And," he refers us back to those former things, in this meaning. The children have not hearkened to what the Lord commanded, sending to them by His servants the prophets, but have hardened their necks and given themselves up to do evil before the Lord and provoke Him to anger; "and" therefore "the word of the Lord came to Jonah, saying, Arise and go to Nineveh that great city, and preach unto her," that so Israel may be shewn, in comparison with the pagan, to be the more guilty, when the Ninevites should repent, the children of Israel persevered in unrepentance."
Jonah the son of Amittai - Both names occur here only in the Old Testament, Jonah signifies "Dove," Amittai, "the truth of God." Some of the names of the Hebrew prophets so suit in with their times, that they must either have been given them propheticly, or assumed by themselves, as a sort of watchword, analogous to the prophetic names, given to the sons of Hosea and Isaiah. Such were the names of Elijah and Elisha, "The Lord is my God," "my God is salvation." Such too seems to be that of Jonah. The "dove" is everywhere the symbol of "mourning love." The side of his character which Jonah records is that of his defect, his want of trust in God, and so his unloving zeal against those, who were to be the instruments of God against his people. His name perhaps preserves that character by which he willed to be known among his people, one who moaned or mourned over them.
Arise, go to Nineveh, that great city - The Assyrian history, as far as it has yet been discovered, is very bare of events in regard to this period. We have as yet the names of three kings only for 150 years. But Assyria, as far as we know its history, was in its meridian. Just before the time of Jonah, perhaps ending in it, were the victorious reigns of Shalmanubar and Shamasiva; after him was that of Ivalush or Pul, the first aggressor upon Israel. It is clear that this was a time Of Assyrian greatness: since God calls it "that great city," not in relation to its extent only, but its power. A large weak city would not have been called a "great city unto God" Jon 3:3.
And cry against it - The substance of that cry is recorded afterward, but God told to Jonah now, what message he was to cry aloud to it. For Jonah relates afterward, how he expostulated now with God, and that his expostulation was founded on this, that God was so merciful that He would not fulfill the judgment which He threatened. Faith was strong in Jonah, while, like Apostles "the sons of thunder," before the Day of Pentecost, he knew not" what spirit he was of." Zeal for the people and, as he doubtless thought, for the glory of God, narrowed love in him. He did not, like Moses, pray Exo 32:32, "or else blot me also out of Thy book," or like Paul, desire even to be "an anathema from Christ" Rom 9:3 for his people's sake, so that there might be more to love his Lord. His zeal was directed, like that of the rebuked Apostles, against others, and so it too was rebuked. But his faith was strong. He shrank back from the office, as believing, not as doubting, the might of God. He thought nothing of preaching, amid that multitude of wild warriors, the stern message of God. He was willing, alone, to confront the violence of a city of 600,000, whose characteristic was violence. He was ready, at God's bidding, to enter what Nahum speaks of as a den of lions Nah 2:11-12; "The dwelling of the lions and the feeding-place of the young lions, where the lion did tear in pieces enough for his whelps, and strangled for his lionesses." He feared not the fierceness of their lion-nature, but God's tenderness, and lest that tenderness should be the destruction of his own people.
Their wickedness is come up before Me - So God said to Cain, Gen 4:10. "The voice of thy brother's blood crieth unto Me from the ground:" and of Sodom Gen 18:20 :21, "The cry of Sodom and Gomorrah is great, because their sin is very grievous; the cry of it is come up unto Me." The "wickedness" is not the mere mass of human sin, of which it is said Jo1 5:19, "the whole world lieth in wickedness," but evil-doing toward others. This was the cause of the final sentence on Nineveh, with which Nahum closes his prophecy, "upon whom hath not thy wickedness passed continually?" It bad been assigned as the ground of the judgment on Israel through Nineveh Hos 10:14-15. "So shall Bethel do unto you, on account of the wickedness of your wickedness." It was the ground of the destruction by the flood Gen 6:5. "God saw that the wickedness of man was great upon the earth." God represents Himself, the Great Judge, as sitting on His Throne in heaven, Unseen but All-seeing, to whom the wickedness and oppressiveness of man against man "goes up," appealing for His sentence against the oppressor. The cause seems ofttimes long in pleading. God is long-suffering with the oppressor too, that if so be, he may repent. So would a greater good come to the oppressed also, if the wolf became a lamb. But meanwhile, " every iniquity has its own voice at the hidden judgment seat of God." Mercy itself calls for vengeance on the unmerciful.
But (And) Jonah rose up to flee ... from the presence of the Lord - literally "from being before the Lord." Jonah knew well, that man could not escape from the presence of God, whom he knew as the Self-existing One, He who alone is, the Maker of heaven, earth and sea. He did not "flee" then "from His presence," knowing well what David said Psa 139:7, Psa 139:9-10, "whither shall I go from Thy Spirit, or whither shall I flee from Thy presence? If I take the wings of the morning, and dwell in the uttermost parts of the sea, even there shall Thy hand lead me and Thy right hand shall hold me." Jonah fled, not from God's presence, but from standing before him, as His servant and minister. He refused God's service, because, as he himself tells God afterward Jon 4:2, he knew what it would end in, and he misliked it.
So he acted, as people often do, who dislike God's commands. He set about removing himself as far as possible from being under the influence of God, and from the place where he "could" fulfill them. God commanded him to go to Nineveh, which lay northeast from his home; and he instantly set himself to flee to the then furthermost west. Holy Scripture sets the rebellion before us in its full nakedness. "The word of the Lord came unto Jonah, go to Nineveh, and Jonah rose up;" he did something instantly, as the consequence of God's command. He "rose up," not as other prophets, to obey, but to disobey; and that, not slowly nor irresolutely, but "to flee, from" standing "before the Lord." He renounced his office. So when our Lord came in the flesh, those who found what He said to be "hard sayings," went away from Him, "and walked no more with Him" Joh 6:66. So the rich "young man went away sorrowful Mat 19:22, for he had great possessions."
They were perhaps afraid of trusting themselves in His presence; or they were ashamed of staying there, and not doing what He said. So men, when God secretly calls them to prayer, go and immerse themselves in business; when, in solitude, He says to their souls something which they do not like, they escape His Voice in a throng. If He calls them to make sacrifices for His poor, they order themselves a new dress or some fresh sumptuousness or self-indulgence; if to celibacy, they engage themselves to marry immediately; or, contrariwise, if He calls them not to do a thing, they do it at once, to make an end of their struggle and their obedience; to put obedience out of their power; to enter themselves on a course of disobedience. Jonah, then, in this part of his history, is the image of those who, when God calls them, disobey His call, and how He deals with them, when he does not abandon them. He lets them have their way for a time, encompasses them with difficulties, so that they shall "flee back from God displeased to God appeased."
"The whole wisdom, the whole bliss, the whole of man lies in this, to learn what God wills him to do, in what state of life, calling, duties, profession, employment, He wills him to serve Him." God sent each one of us into the world, to fulfill his own definite duties, and, through His grace, to attain to our own perfection in and through fulfilling them. He did not create us at random, to pass through the world, doing whatever self-will or our own pleasure leads us to, but to fulfill His will. This will of His, if we obey His earlier calls, and seek Him by prayer, in obedience, self-subdual, humility, thoughtfulness, He makes known to each by His own secret drawings, and, in absence of these, at times by His Providence or human means. And then , "to follow Him is a token of predestination." It is to place ourselves in that order of things, that pathway to our eternal mansion, for which God created us, and which God created for us.
So Jesus says Joh 10:27-28, "My sheep hear My voice and I know them, and they follow Me, and I give unto them eternal life, and they shall never perish, neither shall any man pluck them out of My Hand." In these ways, God has foreordained for us all the graces which we need; in these, we shall be free from all temptations which might be too hard for us, in which our own special weakness would be most exposed. Those ways, which people choose out of mere natural taste or fancy, are mostly those which expose them to the greatest peril of sin and damnation. For they choose them, just because such pursuits flatter most their own inclinations, and give scope to their natural strength and their moral weakness. So Jonah, disliking a duty, which God gave him to fulfill, separated himself from His service, forfeited his past calling, lost, as far as in him lay, his place among "the goodly fellowship of the prophets," and, but for God's overtaking grace, would have ended his days among the disobedient. As in Holy Scripture, David stands alone of saints, who had been after their calling, bloodstained; as the penitent robber stands alone converted in death; as Peter stands singly, recalled after denying his Lord; so Jonah stands, the one prophet, who, having obeyed and then rebelled, was constrained by the overpowering providence and love of God, to return and serve Him.
"Being a prophet, Jonah could not be ignorant of the mind of God, that, according to His great Wisdom and His unsearchable judgments and His untraceable and incomprehensible ways, He, through the threat, was providing for the Ninevites that they should not suffer the things threatened. To think that Jonah hoped to hide himself in the sea and elude by flight the great Eye of God, were altogether absurd and ignorant, which should not be believed, I say not of a prophet, but of no other sensible person who had any moderate knowledge of God and His supreme power. Jonah knew all this better than anyone, that, planning his flight, he changed his place, but did not flee God. For this could no man do, either by hiding himself in the bosom of the earth or depths of the sea or ascending (if possible) with wings into the air, or entering the lowest hell, or encircled with thick clouds, or taking any other counsel to secure his flight.
This, above all things and alone, can neither be escaped nor resisted, God. When He willeth to hold and grasp in His Hand, He overtaketh the swift, baffleth the intelligent, overthroweth the strong, boweth the lofty, tameth rashness, subdueth might. He who threatened to others the mighty Hand of God, was not himself ignorant of nor thought to flee, God. Let us not believe this. But since he saw the fall of Israel and perceived that the prophetic grace would pass over to the Gentiles, he withdrew himself from the office of preaching, and put off the command." "The prophet knoweth, the Holy Spirit teaching him, that the repentance of the Gentiles is the ruin of the Jews. A lover then of his country, he does not so much envy the deliverance of Nineveh, as will that his own country should not perish. - Seeing too that his fellow-prophets are sent to the lost sheep of the house of Israel, to excite the people to repentance, and that Balaam the soothsayer too prophesied of the salvation of Israel, he grieveth that he alone is chosen to be sent to the Assyrians, the enemies of Israel, and to that greatest city of the enemies where was idolatry and ignorance of God. Yet more he feared lest they, on occasion of his preaching, being converted to repentance, Israel should be wholly forsaken. For he knew by the same Spirit whereby the preaching to the Gentiles was entrusted to him, that the house of Israel would then perish; and he feared that what was at one time to be, should take place in his own time." "The flight of the prophet may also be referred to that of man in general who, despising the commands of God, departed from Him and gave himself to the world, where subsequently, through the storms of ill and the wreck of the whole world raging against him, he was compelled to feel the presence of God, and to return to Him whom he had fled. Whence we understand, that those things also which men think for their good, when against the will of God, are turned to destruction; and help not only does not benefit those to whom it is given, but those too who give it, are alike crushed. As we read that Egypt was conquered by the Assyrians, because it helped Israel against the will of God. The ship is emperiled which had received the emperiled; a tempest arises in a calm; nothing is secure, when God is against us."
Tarshish - , named after one of the sons of Javan, Gen 10:4. was an ancient merchant city of Spain, once proverbial for its wealth (Psa 72:10. Strabo iii. 2. 14), which supplied Judaea with silver Jer 10:9, Tyre with "all manner of riches," with iron also, tin, lead. Eze 27:12, Eze 27:25. It was known to the Greeks and Romans, as (with a harder pronunciation) Tartessus; but in our first century, it had either ceased to be, or was known under some other name. Ships destined for a voyage, at that time, so long, and built for carrying merchandise, were naturally among the largest then constructed. "Ships of Tarshish" corresponded to the "East-Indiamen" which some of us remember. The breaking of "ships of Tarshish by the East Wind" Psa 48:7 is, on account of their size and general safety, instanced as a special token of the interposition of God.
And went down to Joppa - Joppa, now Jaffa (Haifa), was the one well-known port of Israel on the Mediterranean. There the cedars were brought from Lebanon for both the first and second temple Ch2 3:16; Ezr 2:7. Simon the Maccabee (1 Macc. 14:5) "took it again for a haven, and made an entrance to the isles of the sea." It was subsequently destroyed by the Romans, as a pirate-haven. (Josephus, B. J. iii. 9. 3, and Strabo xvi. 2. 28.) At a later time, all describe it as an unsafe haven. Perhaps the shore changed, since the rings, to which Andromeda was tabled to have been fastened, and which probably were once used to moor vessels, were high above the sea. Perhaps, like the Channel Islands, the navigation was safe to those who knew the coast, unsafe to others. To this port Jonah "went down" from his native country, the mountain district of Zabulon. Perhaps it was not at this time in the hands of Israel. At least, the sailors were pagan. He "went down," as the man who fell among the thieves, is said to "have gone down from Jerusalem to Jericho." Luk 10:30. He "went down" from the place which God honored by His presence and protection.
And he paid the fare thereof - Jonah describes circumstantially, how he took every step to his end. He went down, found a strongly built ship going where he wished, paid his fare, embarked. He seemed now to have done all. He had severed himself from the country where his office lay. He had no further step to take. Winds and waves would do the rest. He had but to be still. He went, only to be brought back again.
"Sin brings our soul into much senselessness. For as those overtaken by heaviness of head and drunkenness, are borne on simply and at random, and, be there pit or precipice or whatever else below them, they fall into it unawares; so too, they who fall into sin, intoxicated by their desire of the object, know not what they do, see nothing before them, present or future. Tell me, Fleest thou the Lord? Wait then a little, and thou shalt learn from the event, that thou canst not escape the hands of His servant, the sea. For as soon as he embarked, it too roused its waves and raised them up on high; and as a faithful servant, finding her fellow-slave stealing some of his master's property, ceases not from giving endless trouble to those who take him in, until she recover him, so too the sea, finding and recognizing her fellow-servant, harasses the sailors unceasingly, raging, roaring, not dragging them to a tribunal but threatening to sink the vessel with all its unless they restore to her, her fellow-servant."
"The sinner "arises," because, will he, nill he, toil he must. If he shrinks from the way of God, because it is hard, he may not yet be idle. There is the way of ambition, of covetousness, of pleasure, to be trodden, which certainly are far harder. 'We wearied ourselves (Wisdom 5:7),' say the wicked, 'in the way of wickedness and destruction, yea, we have gone through deserts where there lay no way; but the way of the Lord we have not known.' Jonah would not arise, to go to Nineveh at God's command; yet he must needs arise, to flee to Tarshish from before the presence of God. What good can he have who fleeth the Good? what light, who willingly forsaketh the Light? "He goes down to Joppa." Wherever thou turnest, if thou depart from the will of God, thou goest down. Whatever glory, riches, power, honors, thou gainest, thou risest not a whit; the more thou advancest, while turned from God, the deeper and deeper thou goest down. Yet all these things are not had, without paying the price. At a price and with toil, he obtains what he desires; he receives nothing gratis, but, at great price purchases to himself storms, griefs, peril. There arises a great tempest in the sea, when various contradictory passions arise in the heart of the sinner, which take from him all tranquility and joy. There is a tempest in the sea, when God sends strong and dangerous disease, whereby the frame is in peril of being broken. There is a tempest in the sea, when, thro' rivals or competitors for the same pleasures, or the injured, or the civil magistrate, his guilt is discovered, he is laden with infamy and odium, punished, withheld from his wonted pleasures. Psa 107:23-27. "They who go down to the sea of this world, and do business in mighty waters - their soul melteth away because of trouble; they reel to and fro and stagger like a drunken man, and all their wisdom is swallowed up."
But (And) the Lord sent out - (literally 'cast along'). Jonah had done his all. Now God's part began. This He expresses by the word, "And." Jonah took "his" measures, "and" now God takes "His." He had let him have his way, as He often deals with those who rebel against Him. He lets them have their way up to a certain point. He waits, in the tranquility of His Almightiness, until they have completed their preparations; and then, when man has ended, He begins, that man may see the more that it is His doing . "He takes those who flee from Him in their flight, the wise in their counsels, sinners in their conceits and sins, and draws them back to Himself and compels them to return. Jonah thought to find rest in the sea, and lo! a tempest." Probably, God summoned back Jonah, as soon as he had completed all on his part, and sent the tempest, soon after he left the shore.
At least, such tempests often swept along that shore, and were known by their own special name, like the Euroclydon off Crete. Jonah too alone had gone down below deck to sleep, and, when the storm came, the mariners thought it possible to put back. Josephus says of that shore, "Joppa having by nature no haven, for it ends in a rough shore, mostly abrupt, but for a short space having projections, i. e., deep rocks and cliffs advancing into the sea, inclining on either side toward each other (where the traces of the chains of Andromeda yet shown accredit the antiquity of the fable,) and the north wind beating right on the shore, and dashing the high waves against the rocks which receive them, makes the station there a harborless sea. As those from Joppa were tossing here, a strong wind (called by those who sail here, the black north wind) falls upon them at daybreak, dashing straightway some of the ships against each other, some against the rocks, and some, forcing their way against the waves to the open sea, (for they fear the rocky shore ...) the breakers towering above them, sank."
The ship was like - (literally 'thought') To be broken Perhaps Jonah means by this very vivid image to exhibit the more his own dullness. He ascribes, as it were, to the ship a sense of its own danger, as she heaved and rolled and creaked and quivered under the weight of the storm which lay on her, and her masts groaned, and her yard-arms shivered. To the awakened conscience everything seems to have been alive to God's displeasure, except itself.
And cried, every man unto his God - They did what they could. "Not knowing the truth, they yet know of a Providence, and, amid religious error, know that there is an Object of reverence." In ignorance they had received one who offended God. And now God, "whom they ignorantly worshiped" Act 17:23, while they cried to the gods, who, they thought, disposed of them, heard them. They escaped with the loss of their wares, but God saved their lives and revealed Himself to them. God hears ignorant prayer, when ignorance is not willful and sin.
To lighten it of them - , literally "to lighten from against them, to lighten" what was so much "against them," what so oppressed them. "They thought that the ship was weighed down by its wonted lading, and they knew not that the whole weight was that of the fugitive prophet." "The sailors cast forth their wares," but the ship was not lightened. For the whole weight still remained, the body of the prophet, that heavy burden, not from the nature of the body, but from the burden of sin. For nothing is so onerous and heavy as sin and disobedience. Whence also Zechariah Zac 5:7 represented it under the image of lead. And David, describing its nature, said Psa 38:4, "my wickednesses are gone over my head; as a heavy burden they are too heavy for me." And Christ cried aloud to those who lived in many sins, Mat 11:28. "Come unto Me, all ye that labor and are heavy-laden, and I will refresh you."
Jonah was gone down - , probably before the beginning of the storm, not simply before the lightening of the vessel. He could hardly have fallen asleep "then." A pagan ship was a strange place for a prophet of God, not as a prophet, but as a fugitive; and so, probably, ashamed of what he had completed, he had withdrawn from sight and notice. He did not embolden himself in his sin, but shrank into himself. The conscience most commonly awakes, when the sin is done. It stands aghast as itself; but Satan, if he can, cuts off its retreat. Jonah had no retreat now, unless God had made one.
And was fast asleep - The journey to Joppa had been long and hurried; he had "fled." Sorrow and remorse completed what fatigue began. Perhaps he had given himself up to sleep, to dull his conscience. For it is said, "he lay down and was fast asleep." Grief produces sleep; from where it is said of the apostles in the night before the Lord's Passion, when Jesus "rose up from prayer and was come to His disciples, He found them sleeping for sorrow" Luk 22:45 . "Jonah slept heavily. Deep was the sleep, but it was not of pleasure but of grief; not of heartlessness, but of heavy-heartedness. For well-disposed servants soon feel their sins, as did he. For when the sin has been done, then he knows its frightfulness. For such is sin. When born, it awakens pangs in the soul which bare it, contrary to the law of our nature. For so soon as we are born, we end the travail-pangs; but sin, so soon as born, rends with pangs the thoughts which conceived it." Jonah was in a deep sleep, a sleep by which he was fast held and bound; a sleep as deep as that from which Sisera never woke. Had God allowed the ship to sink, the memory of Jonah would have been that of the fugitive prophet. As it is, his deep sleep stands as an image of the lethargy of sin . "This most deep sleep of Jonah signifies a man torpid and slumbering in error, to whom it sufficed not to flee from the face of God, but his mind, drowned in a stupor and not knowing the displeasure of God, lies asleep, steeped in security."
What meanest thou? - or rather, "what aileth thee?" (literally "what is to thee?") The shipmaster speaks of it (as it was) as a sort of disease, that he should be thus asleep in the common peril. "The shipmaster," charged, as he by office was, with the common weal of those on board, would, in the common peril, have one common prayer. It was the prophet's office to call the pagan to prayers and to calling upon God. God reproved the Scribes and Pharisees by the mouth of the children who "cried Hosanna" Mat 21:15; Jonah by the shipmaster; David by Abigail; Sa1 25:32-34; Naaman by his servants. Now too he reproves worldly priests by the devotion of laymen, sceptic intellect by the simplicity of faith.
If so be that God will think upon us - , (literally "for us") i. e., for good; as David says, Psa 40:17. "I am poor and needy, the Lord thinketh upon" (literally "for") "me." Their calling upon their own gods had failed them. Perhaps the shipmaster had seen something special about Jonah, his manner, or his prophet's garb. He does not only call Jonah's God, "thy" God, as Darius says to Daniel "thy God" Dan 6:20, but also "the God," acknowledging the God whom Jonah worshiped, to be "the God." It is not any pagan prayer which he asks Jonah to offer. It is the prayer of the creature in its need to God who can help; but knowing its own ill-desert, and the separation between itself and God, it knows not whether He will help it. So David says Psa 25:7, "Remember not the sins of my youth nor my transgressions; according to Thy mercy remember Thou me for Thy goodness' sake, O Lord."
"The shipmaster knew from experience, that it was no common storm, that the surges were an infliction borne down from God, and above human skill, and that there was no good in the master's skill. For the state of things needed another Master who ordereth the heavens, and craved the guidance from on high. So then they too left oars, sails, cables, gave their hands rest from rowing, and stretched them to heaven and called on God."
Come, and let us cast lots - Jonah too had probably prayed, and his prayers too were not heard. Probably, too, the storm had some unusual character about it, the suddenness with which it burst upon them, its violence, the quarter from where it came, its whirlwind force . "They knew the nature of the sea, and, as experienced sailors, were acquainted with the character of wind and storm, and had these waves been such as they had known before, they would never have sought by lot for the author of the threatened wreck, or, by a thing uncertain, sought to escape certain peril." God, who sent the storm to arrest Jonah and to cause him to be cast into the sea, provided that its character should set the mariners on divining, why it came. Even when working great miracles, God brings about, through man, all the forerunning events, all but the last act, in which He puts forth His might. As, in His people, he directed the lot to fall upon Achan or upon Jonathan, so here He overruled the lots of the pagan sailors to accomplish His end. " We must not, on this precedent, immediately trust in lots, or unite with this testimony that from the Acts of the Apostles, when Matthias was by lot elected to the apostolate, since the privileges of individuals cannot form a common law." "Lots," according to the ends for which they were cast, were for:
i) The lot for dividing is not wrong if not used,
1) "without any necessity, for this would be to tempt God:"
2) "if in case of necessity, not without reverence of God, as if Holy Scripture were used for an earthly end," as in determining any secular matter by opening the Bible:
3) for objects which ought to be decided otherwise, (as, an office ought to be given to the fittest:)
4) in dependence upon any other than God Pro 16:33. "The lot is cast into the lap, but the whole disposing of it is the Lord's." So then they are lawful "in secular things which cannot otherwise be conveniently distributed," or when there is no apparent reason why, in any advantage or disadvantage, one should be preferred to another." Augustine even allows that, in a time of plague or persecution, the lot might be cast to decide who should remain to administer the sacraments to the people, lest, on the one side, all should be taken away, or, on the other, the Church be deserted.
ii.) The lot for consulting, i. e., to decide what one should do, is wrong, unless in a matter of mere indifference, or under inspiration of God, or in some extreme necessity where all human means fail.
iii.) The lot for divining, i. e., to learn truth, whether of things present or future, of which we can have no human knowledge, is wrong, except by direct inspiration of God. For it is either to tempt God who has not promised so to reveal things, or, against God, to seek superhuman knowledge by ways unsanctioned by Him. Satan may readily mix himself unknown in such inquiries, as in mesmerism. Forbidden ground is his own province.
God overruled the lot in the case of Jonah, as He did the sign which the Philistines sought . "He made the heifers take the way to Bethshemesh, that the Philistines might know that the plague came to them, not by chance, but from Hilmself" . "The fugitive (Jonah) was taken by lot, not by any virtue of the lots, especially the lots of pagan, but by the will of Him who guided the uncertain lots" "The lot betrayed the culprit. Yet not even thus did they cast him over; but, even while such a tumult and storm lay on them, they held, as it were, a court in the vessel, as though in entire peace, and allowed him a hearing and defense, and sifted everything accurately, as men who were to give account of their judgment. Hear them sifting all as in a court - The roaring sea accused him; the lot convicted and witnessed against him, yet not even thus did they pronounce against him - until the accused should be the accuser of his own sin. The sailors, uneducated, untaught, imitated the good order of courts. When the sea scarcely allowed them to breathe, whence such forethought about the prophet? By the disposal of God. For God by all this instructed the prophet to be humane and mild, all but saying aloud to him; 'Imitate these uninstructed sailors. They think not lightly of one soul, nor are unsparing as to one body, thine own. But thou, for thy part, gavest up a whole city with so many myriads. They, discovering thee to be the cause of the evils which befell them, did not even thus hurry to condemn thee. Thou, having nothing whereof to accuse the Ninevites, didst sink and destroy them. Thou, when I bade thee go and by thy preaching call them to repentance, obeyedst not; these, untaught, do all, compass all, in order to recover thee, already condemned, from punishment.'"
Tell us, for whose cause - Literally "for what to whom." It may be that they thought that Jonah had been guilty toward some other. The lot had pointed him out. The mariners, still fearing to do wrong, ask him thronged questions, to know why the anger of God followed him; "what" hast thou done "to whom?" "what thine occupation?" i. e., either his ordinary occupation, whether it was displeasing to God? or this particular business in which he was engaged, and for which he had come on board. Questions so thronged have been admired in human poetry, Jerome says. For it is true to nature. They think that some one of them will draw forth the answer which they wish. It may be that they thought that his country, or people, or parents, were under the displeasure of God. But perhaps, more naturally, they wished to "know all about him," as people say. These questions must have gone home to Jonah's conscience. "What is thy business?" The office of prophet which he had left. "Whence comest thou?" From standing before God, as His minister. "What thy country? of what people art thou?" The people of God, whom he had quitted for pagan; not to win them to God, as He commanded; but, not knowing what they did, to abet him in his flight.
What is thine occupation? - They should ask themselves, who have Jonah's office to speak in the name of God, and preach repentance . "What should be thy business, who hast consecrated thyself wholly to God, whom God has loaded with daily benefits? who approachest to Him as to a Friend? "What is thy business?" To live for God, to despise the things of earth, to behold the things of heaven," to lead others heavenward.
Jonah answers simply the central point to which all these questions tended:
I am an Hebrew - This was the name by which Israel was known to foreigners. It is used in the Old Testament, only when they are spoken of by foreigners, or speak of themselves to foreigners, or when the sacred writers mention them in contrast with foreigners . So Joseph spoke of his land Gen 40:15, and the Hebrew midwives Exo 1:19, and Moses' sister Exo 2:7, and God in His commission to Moses Exo 3:18; Exo 7:16; Exo 9:1 as to Pharaoh, and Moses in fulfilling it Exo 5:3. They had the name, as having passed the River Euphrates, "emigrants." The title might serve to remind themselves, that they were "strangers" and "pilgrims," Heb 11:13. whose fathers had left their home at God's command and for God , "passers by, through this world to death, and through death to immortality."
And I fear the Lord - , i. e., I am a worshiper of Him, most commonly, one who habitually stands in awe of Him, and so one who stands in awe of sin too. For none really fear God, none fear Him as sons, who do not fear Him in act. To be afraid of God is not to fear Him. To be afraid of God keeps men away from God; to fear God draws them to Him. Here, however, Jonah probably meant to tell them, that the Object of his fear and worship was the One Self-existing God, He who alone is, who made all things, in whose hands are all things. He had told them before, that he had fled "from being before Yahweh." They had not thought anything of this, for they thought of Yahweh, only as the God of the Jews. Now he adds, that He, Whose service he had thus forsaken, was "the God of heaven, Who made the sea and dry land," that sea, whose raging terrified them and threatened their lives. The title, "the God of heaven," asserts the doctrine of the creation of the heavens by God, and His supremacy.
Hence, Abraham uses it to his servant Gen 24:7, and Jonah to the pagan mariners, and Daniel to Nebuchadnezzar Dan 2:37, Dan 2:44; and Cyrus in acknowledging God in his proclamation Ch2 36:23; Ezr 1:2. After his example, it is used in the decrees of Darius Ezr 6:9-10 and Artaxerxes Ezr 7:12, Ezr 7:21, Ezr 7:23, and the returned exiles use it in giving account of their building the temple to the Governor Ezr 5:11-12. Perhaps, from the habit of contact with the pagan, it is used once by Daniel Dan 2:18 and by Nehemiah Neh 1:4-5; Neh 2:4, Neh 2:20. Melchizedek, not perhaps being acquainted with the special name, Yahweh, blessed Abraham in the name of "God, the Possessor" or "Creator of heaven and earth" Gen 14:19, i. e., of all that is. Jonah, by using it, at once taught the sailors that there is One Lord of all, and why this evil had fallen on them, because they had himself with them, the renegade servant of God. "When Jonah said this, he indeed feared God and repented of his sin. If he lost filial fear by fleeing and disobeying, he recovered it by repentance."
Then were the men exceedingly afraid - Before, they had feared the tempest and the loss of their lives. Now they feared God. They feared, not the creature but the Creator. They knew that what they had feared was the doing of His Almightiness. They felt how awesome a thing it was to be in His Hands. Such fear is the beginning of conversion, when people turn from dwelling on the distresses which surround them, to God who sent them.
Why hast thou done this? - They are words of amazement and wonder. Why hast thou not obeyed so great a God, and how thoughtest thou to escape the hand of the Creator ? "What is the mystery of thy flight? Why did one, who feared God and had revelations from God, flee, sooner than go to fulfill them? Why did the worshiper of the One true God depart from his God?" "A servant flee from his Lord, a son from his father, man from his God!" The inconsistency of believers is the marvel of the young Christian, the repulsion of those without, the hardening of the unbeliever. If people really believed in eternity, how could they be thus immersed in things of time? If they believed in hell, how could they so hurry there? If they believed that God died for them, how could they so requite Him? Faith without love, knowledge without obedience, conscious dependence and rebellion, to be favored by God yet to despise His favor, are the strangest marvels of this mysterious world.
All nature seems to cry out to and against the unfaithful Christian, "why hast thou done this?" And what a why it is! A scoffer has recently said so truthfully : "Avowed scepticism cannot do a tenth part of the injury to practical faith, that the constant spectacle of the huge mass of worldly unreal belief does." It is nothing strange, that the world or unsanctified intellect should reject the Gospel. It is a thing of course, unless it be converted. But, to know, to believe, and to DISOBEY! To disobey God, in the name of God. To propose to halve the living Gospel, as the woman who had killed her child Kg1 3:26, and to think that the poor quivering remnants would be the living Gospel anymore! As though the will of God might, like those lower forms of His animal creation, be divided endlessly, and, keep what fragments we will, it would still be a living whole, a vessel of His Spirit! Such unrealities and inconsistencies would be a sore trial of faith, had not Jesus, who (cf. Joh 2:25), "knew what is in man," forewarned us that it should be so. The scandals against the Gospel, so contrary to all human opinion, are only all the more a testimony to the divine knowledge of the Redeemer.
What shall we do unto thee? - They knew him to be a prophet; they ask him the mind of his God. The lots had marked out Jonah as the cause of the storm; Jonah had himself admitted it, and that the storm was for "his" cause, and came from "his" God . "Great was he who fled, greater He who required him. They dare not give him up; they cannot conceal him. They blame the fault; they confess their fear; they ask "him" the remedy, who was the author of the sin. If it was faulty to receive thee, what can we do, that God should not be angered? It is thine to direct; ours, to obey."
The sea wrought and was tempestuous - , literally "was going and whirling." It was not only increasingly tempestuous, but, like a thing alive and obeying its Master's will, it was holding on its course, its wild waves tossing themselves, and marching on like battalions, marshalled, arrayed for the end for which they were sent, pursuing and demanding the runaway slave of God . "It was going, as it was bidden; it was going to avenge its Lord; it was going, pursuing the fugitive prophet. It was swelling every moment, and, as though the sailors were too tardy, was rising in yet greater surges, shewing that the vengeance of the Creator admitted not of delay."
Take me up, and cast me into the sea - Neither might Jonah have said this, nor might the sailors have obeyed it, without the command of God. Jonah might will alone to perish, who had alone offended; but, without the command of God, the Giver of life, neither Jonah nor the sailors might dispose of the life of Jonah. But God willed that Jonah should be cast into the sea - where he had gone for refuge - that (Wisdom 11:16) wherewithal he had "sinned, by the same also he might be punished" as a man; and, as a prophet, that he might, in his three days' burial, prefigure Him who, after His Resurrection, should convert, not Nineveh, but the world, the cry of whose wickedness went up to God.
For I know that for my sake - o "In that he says, "I know," he marks that he had a revelation; in that he says, "this great storm," he marks the need which lay on those who cast him into the sea."
The men rowed hard - , literally "dug." The word, like our "plowed the main," describes the great efforts which they made. Amid the violence of the storm, they had furled their sails. These were worse than useless. The wind was off shore, since by rowing alpine they hoped to get back to it. They put their oars well and firmly in the sea, and turned up the water, as men turn up earth by digging. But in vain! God willed it not. The sea went on its way, as before. In the description of the deluge, it is repeated Gen 7:17-18, "the waters increased and bare up the ark, and it was lifted up above the earth; the waters increased greatly upon the earth; and the ark went upon the face of the waters." The waters raged and swelled, drowned the whole world, yet only bore up the ark, as a steed bears its rider: man was still, the waters obeyed. In this tempest, on the contrary, man strove, but, instead of the peace of the ark, the burden is, the violence of the tempest; "the sea wrought and was tempestuous against them" . "The prophet had pronounced sentence against himself, but they would not lay hands upon him, striving hard to get back to land, and escape the risk of bloodshed, willing to lose life rather than cause its loss. O what a change was there. The people who had served God, said, Crucify Him, Crucify Him! These are bidden to put to death; the sea rageth; the tempest commandeth; and they are careless its to their own safety, while anxious about another's."
Wherefore (And) they cried unto the Lord - "They cried" no more "each man to his god," but to the one God, whom Jonah had made known to them; and to Him they cried with an earnest submissive, cry, repeating the words of beseeching, as men, do in great earnestness; "we beseech Thee, O Lord, let us not, we beseech Thee, perish for the life of this man" (i. e., as a penalty for taking it, as it is said, Sa2 14:7. "we will slay him for the life of his brother," and, Deu 19:21. "life for life.") They seem to have known what is said, Gen 9:5-6. "your blood of your lives will I require; at the hand of every beast will I require it and at the hand of man; at the hand of every man's brother will I require the life of man. Whoso sheddeth man's blood, by man shall his blood be shed, for in the image of God made He man" , "Do not these words of the sailors seem to us to be the confession of Pilate, who washed his hands, and said, 'I am clean from the blood of this Man?' The Gentiles would not that Christ should perish; they protest that His Blood is innocent."
And lay not upon us innocent blood - innocent as to them, although, as to this thing, guilty before God, and yet, as to God also, more innocent, they would think, than they. For, strange as this was, one disobedience, their whole life, they now knew, was disobedience to God; His life was but one act in a life of obedience. If God so punishes one sin of the holy Pe1 4:18, "where shall the ungodly and sinner appear?" Terrible to the awakened conscience are God's chastenings on some (as it seems) single offence of those whom He loves.
For Thou, Lord, (Who knowest the hearts of all men,) hast done, as it pleased Thee - Wonderful, concise, confession of faith in these new converts! Psalmists said it, Psa 135:6; Psa 115:3. "Whatsoever God willeth, that doeth He in heaven and in earth, in the sea and in all deep places." But these had but just known God, and they resolve the whole mystery of man's agency and God's Providence into the three simple words , as (Thou) "willedst" (Thou) "didst." "That we took him aboard, that the storm ariseth, that the winds rage, that the billows lift themselves, that the fugitive is betrayed by the lot, that he points out what is to be done, it is of Thy will, O Lord" . "The tempest itself speaketh, that 'Thou, Lord, hast done as Thou willedst.' Thy will is fulfilled by our hands." "Observe the counsel of God, that, of his own will, not by violence or by necessity, should he be cast into the sea. For the casting of Jonah into the sea signified the entrance of Christ into the bitterness of the Passion, which He took upon Himself of His own will, not of necessity. Isa 53:7. "He was offered up, and He willingly submitted Himself." And as those who sailed with Jonah were delivered, so the faithful in the Passion of Christ. Joh 18:8-9. "If ye seek Me, let these go their way, that the saying might be fulfilled which" Jesus spake, 'Of them which Thou gavest Me, I have lost none. '"
They took up Jonah - o "He does not say, 'laid hold on him', nor 'came upon him' but 'lifted' him; as it were, bearing him with respect and honor, they cast him into the sea, not resisting, but yielding himself to their will."
The sea ceased (literally "stood") from his raging - Ordinarily, the waves still swell, when the wind has ceased. The sea, when it had received Jonah, was hushed at once, to show that God alone raised and quelled it. It "stood" still, like a servant, when it had accomplished its mission. God, who at all times saith to it Job 38:11, "Hitherto shalt thou come and no further, and here shall thy proud waves be stayed," now unseen, as afterward in the flesh Mat 8:26, "rebuked the winds and the sea, and there was a great calm" . "If we consider the errors of the world before the Passion of Christ, and the conflicting blasts of diverse doctrines, and the vessel, and the whole race of man, i. e., the creature of the Lord, imperiled, and, after His Passion, the tranquility of faith and the peace of the world and the security of all things and the conversion to God, we shall see how, after Jonah was cast in, the sea stood from its raging" . "Jonah, in the sea, a fugitive, shipwrecked, dead, sayeth the tempest-tossed vessel; he sayeth the pagan, aforetime tossed to and fro by the error of the world into divers opinions. And Hosea, Amos, Isaiah, Joel, who prophesied at the same time, could not amend the people in Judaea; whence it appeared that the breakers could not be calmed, save by the death of (Him typified by) the fugitive."
And the men feared the Lord with a great fear - because, from the tranquility of the sea and the ceasing of the tempest, they saw that the prophet's words were true. This great miracle completed the conversion of the mariners. God had removed all human cause of fear; and yet, in the same words as before, he says, "they feared a great fear;" but he adds, "the Lord." It was the great fear, with which even the disciples of Jesus feared, when they saw the miracles which He did, which made even Peter say, Luk 5:8. "Depart from me, for I am a sinful man, O Lord." Events full of wonder had thronged upon them; things beyond nature, and contrary to nature; tidings which betokened His presence, Who had all things in His hands. They had seen "wind and storm fulfilling His word" Psa 148:8, and, forerunners of the fishermen of Galilee, knowing full well from their own experience that this was above nature, they felt a great awe of God. So He commanded His people, "Thou shalt fear the Lord thy God Deu 6:13, for thy good always" Deu 6:24.
And offered a sacrifice - Doubtless, as it was a large decked vessel and bound on a long voyage, they had live creatures on board, which they could offer in sacrifice. But this was not enough for their thankfulness; "they vowed vows." They promised that they would do thereafter what they could not do then ; "that they would never depart from Him whom they had begun to worship." This was true love, not to be content with aught which they could do, but to stretch forward in thought to an abiding and enlarged obedience, as God should enable them. And so they were doubtless enrolled among the people of God, firstfruits from among the pagan, won to God Who overrules all things, through the disobedience and repentance of His prophet. Perhaps, they were the first preachers among the pagan, and their account of their own wonderful deliverance prepared the way for Jonah's mission to Nineveh.
Now the Lord had (literally "And the Lord") prepared - Jonah (as appears from his thanksgiving) was not swallowed at once, but sank to the bottom of the sea, God preserving him in life there by miracle, as he did in the fish's belly. Then, when the seaweed was twined around his head, and he seemed to be already buried until the sea should give up her dead, "God prepared the fish to swallow Jonah" . "God could as easily have kept Jonah alive in the sea as in the fish's belly, but, in order to prefigure the burial of the Lord, He willed him to be within the fish whose belly was as a grave." Jonah, does not say what fish it was; and our Lord too used a name, signifying only one of the very largest fish. Yet it was no greater miracle to create a fish which should swallow Jonah, than to preserve him alive when swallowed . "The infant is buried, as it were, in the womb of its mother; it cannot breathe, and yet, thus too, it liveth and is preserved, wonderfully nurtured by the will of God." He who preserves the embryo in its living grave can maintain the life of man as easily without the outward air as with it.
The same Divine Will preserves in being the whole creation, or creates it. The same will of God keeps us in life by breathing this outward air, which preserved Jonah without it. How long will men think of God, as if He were man, of the Creator as if He were a creature, as though creation were but one intricate piece of machinery, which is to go on, ringing its regular changes until it shall be worn out, and God were shut up, as a sort of mainspring within it, who might be allowed to be a primal Force, to set it in motion, but must not be allowed to vary what He has once made? "We must admit of the agency of God," say these men when they would not in name be atheists, "once in the beginning of things, but must allow of His interference as sparingly as may be." Most wise arrangement of the creature, if it were indeed the god of its God! Most considerate provision for the non-interference of its Maker, if it could but secure that He would not interfere with it for ever! Acute physical philosophy, which, by its omnipotent word, would undo the acts of God! Heartless, senseless, sightless world, which exists in God, is upheld by God, whose every breath is an effluence of God's love, and which yet sees Him not, thanks Him not, thinks it a greater thing to hold its own frail existence from some imagined law, than to be the object of the tender personal care of the Infinite God who is Love! Poor hoodwinked souls, which would extinguish for themselves the Light of the world, in order that it may not eclipse the rushlight of their own theory!
And Jonah was in the belly of the fish - The time that Jonah was in the fish's belly was a hidden prophecy. Jonah does not explain nor point it. He tells the fact, as Scripture is accustomed to do so. Then he singles out one, the turning point in it. Doubtless in those three days and nights of darkness, Jonah (like him who after his conversion became Paul), meditated much, repented much, sorrowed much, for the love of God, that he had ever offended God, purposed future obedience, adored God with wondering awe for His judgment and mercy. It was a narrow home, in which Jonah, by miracle, was not consumed; by miracle, breathed; by miracle, retained his senses in that fetid place. Jonah doubtless, repented, marveled, adored, loved God. But, of all, God has singled out this one point, how, out of such a place, Jonah thanked God. As He delivered Paul and Silas from the prison, when they prayed with a loud voice to Him, so when Jonah, by inspiration of His Spirit, thanked Him, He delivered him.
To thank God, only in order to obtain fresh gifts from Him, would be but a refined, hypocritical form of selfishness. Such a formal act would not be thanks at all. We thank God, because we love Him, because He is so infinitely good, and so good to us, unworthy. Thanklessness shuts the door to His personal mercies to us, because it makes them the occasion of fresh sins of our's. Thankfulness sets God's essential goodness free (so to speak) to be good to us. He can do what He delights in doing, be good to us, without our making His Goodness a source of harm to us. Thanking Him through His grace, we become fit vessels for larger graces . "Blessed he who, at every gift of grace, returns to Him in whom is all fullness of graces; to whom when we show ourselves not ungrateful for gifts received, we make room in ourselves for grace, and become meet for receiving yet more." But Jonah's was that special character of thankfulness, which thanks God in the midst of calamities from which there was no human exit; and God set His seal on this sort of thankfulness, by annexing this deliverance, which has consecrated Jonah as an image of our Lord, to his wonderful act of thanksgiving.
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|Met proto-oncogene (hepatocyte growth factor receptor)|
Crystallographic structure of MET. PDB rendering based on 1r0p.
|External IDs||ChEMBL: GeneCards:|
|RNA expression pattern|
c-Met (MET or MNNG HOS Transforming gene) is a proto-oncogene that encodes a protein known as hepatocyte growth factor receptor (HGFR). The hepatocyte growth factor receptor protein possesses tyrosine-kinase activity. The primary single chain precursor protein is post-translationally cleaved to produce the alpha and beta subunits, which are disulfide linked to form the mature receptor.
MET is a membrane receptor that is essential for embryonic development and wound healing. Hepatocyte growth factor (HGF) is the only known ligand of the MET receptor. MET is normally expressed by cells of epithelial origin, while expression of HGF is restricted to cells of mesenchymal origin. Upon HGF stimulation, MET induces several biological responses that collectively give rise to a program known as invasive growth.
Abnormal MET activation in cancer correlates with poor prognosis, where aberrantly active MET triggers tumor growth, formation of new blood vessels (angiogenesis) that supply the tumor with nutrients, and cancer spread to other organs (metastasis). MET is deregulated in many types of human malignancies, including cancers of kidney, liver, stomach, breast, and brain. Normally, only stem cells and progenitor cells express MET, which allows these cells to grow invasively in order to generate new tissues in an embryo or regenerate damaged tissues in an adult. However, cancer stem cells are thought to hijack the ability of normal stem cells to express MET, and thus become the cause of cancer persistence and spread to other sites in the body.
MET proto-oncogene (GeneID: 4233) has a total length of 125,982 bp, and it is located in the 7q31 locus of chromosome 7. MET is transcribed into a 6,641 bp mature mRNA, which is then translated into a 1,390 amino-acid MET protein.
MET is a receptor tyrosine kinase (RTK) that is produced as a single-chain precursor. The precursor is proteolytically cleaved at a furin site to yield a highly glycosylated extracellular α-subunit and a transmembrane β-subunit, which are linked together by a disulfide bridge.
- Region of homology to semaphorins (Sema domain), which includes the full α-chain and the N-terminal part of the β-chain
- Cysteine-rich MET-related sequence (MRS domain)
- Glycine-proline-rich repeats (G-P repeats)
- Four immunoglobulin-like structures (Ig domains), a typical protein-protein interaction region.
A Juxtamembrane segment that contains:
- a serine residue (Ser 985), which inhibits the receptor kinase activity upon phosphorylation
- a tyrosine (Tyr 1003), which is responsible for MET polyubiquitination, endocytosis, and degradation upon interaction with the ubiquitin ligase CBL
- Tyrosine kinase domain, which mediates MET biological activity. Following MET activation, transphosphorylation occurs on Tyr 1234 and Tyr 1235
- C-terminal region contains two crucial tyrosines (Tyr 1349 and Tyr 1356), which are inserted into the multisubstrate docking site, capable of recruiting downstream adapter proteins with Src homology-2 (SH2) domains. The two tyrosines of the docking site have been reported to be necessary and sufficient for the signal transduction both in vitro.
MET signaling pathway
MET activation by its ligand HGF induces MET kinase catalytic activity, which triggers transphosphorylation of the tyrosines Tyr 1234 and Tyr 1235. These two tyrosines engage various signal transducers, thus initiating a whole spectrum of biological activities driven by MET, collectively known as the invasive growth program. The transducers interact with the intracellular multisubstrate docking site of MET either directly, such as GRB2, SHC, SRC, and the p85 regulatory subunit of phosphatidylinositol-3 kinase (PI3K), or indirectly through the scaffolding protein Gab1
Tyr 1349 and Tyr 1356 of the multisubstrate docking site are both involved in the interaction with GAB1, SRC, and SHC, while only Tyr 1356 is involved in the recruitment of GRB2, phospholipase C γ (PLC-γ), p85, and SHP2.
GAB1 is a key coordinator of the cellular responses to MET and binds the MET intracellular region with high avidity, but low affinity. Upon interaction with MET, GAB1 becomes phosphorylated on several tyrosine residues which, in turn, recruit a number of signalling effectors, including PI3K, SHP2, and PLC-γ. GAB1 phosphorylation by MET results in a sustained signal that mediates most of the downstream signaling pathways.
Activation of signal transduction
MET engagement activates multiple signal transduction pathways:
- The RAS pathway mediates HGF-induced scattering and proliferation signals, which lead to branching morphogenesis. Of note, HGF, differently from most mitogens, induces sustained RAS activation, and thus prolonged MAPK activity.
- The PI3K pathway is activated in two ways: PI3K can be either downstream of RAS, or it can be recruited directly through the multifunctional docking site. Activation of the PI3K pathway is currently associated with cell motility through remodeling of adhesion to the extracellular matrix as well as localized recruitment of transducers involved in cytoskeletal reorganization, such as RAC1 and PAK. PI3K activation also triggers a survival signal due to activation of the AKT pathway.
- The STAT pathway, together with the sustained MAPK activation, is necessary for the HGF-induced branching morphogenesis. MET activates the STAT3 transcription factor directly, through an SH2 domain.
- The beta-catenin pathway, a key component of the Wnt signaling pathway, translocates into the nucleus following MET activation and participates in transcriptional regulation of numerous genes.
Role in development
During embryonic development, transformation of the flat, two-layer germinal disc into a three-dimensional body depends on transition of some cells from an epithelial phenotype to spindle-shaped cells with motile behaviour, a mesenchymal phenotype. This process is referred to as epithelial-mesenchymal transition (EMT). Later in embryonic development, MET is crucial for gastrulation, angiogenesis, myoblast migration, bone remodeling, and nerve sprouting among others. MET is essential for embryogenesis, because MET -/- mice die in utero due to severe defects in placental development. Furthermore, MET is required for such critical processes as liver regeneration and wound healing during adulthood.
Tissue distribution
MET is normally expressed by epithelial cells. However, MET is also found on endothelial cells, neurons, hepatocytes, hematopoietic cells, and melanocytes. HGF expression is restricted to cells of mesenchymal origin.
Transcriptional control
MET transcription is activated by HGF and several growth factors. MET promoter has four putative binding sites for Ets, a family of transcription factors that control several invasive growth genes. ETS1 activates MET transcription in vitro. MET transcription is activated by hypoxia-inducible factor 1 (HIF1), which is activated by low concentration of intracellular oxygen. HIF1 can bind to one of the several hypoxia response elements (HREs) in the MET promoter. Hypoxia also activates transcription factor AP-1, which is involved in MET transcription.
Role in cancer
MET pathway plays an important role in the development of cancer through:
- angiogenesis (sprouting of new blood vessels from pre-existing ones to supply a tumor with nutrients);
- scatter (cells dissociation due to metalloprotease production), which often leads to metastasis.
Coordinated down-regulation of both MET and its downstream effector extracellular signal-regulated kinase 2 (ERK2) by miR-199a* may be effective in inhibiting not only cell proliferation but also motility and invasive capabilities of tumor cells.
Interaction with tumour suppressor genes
PTEN (phosphatase and tensin homolog) is a tumor suppressor gene encoding a protein PTEN, which possesses lipid and protein phosphatase-dependent as well as phosphatase-independent activities. PTEN protein phosphatase is able to interfere with MET signaling by dephosphorylating either PIP3 generated by PI3K, or the p52 isoform of SHC. SHC dephosphorylation inhibits recruitment of the GRB2 adapter to activated MET.
Cancer therapies targeting HGF/MET
Since tumor invasion and metastasis are the main cause of death in cancer patients, interfering with MET signaling appears to be a promising therapeutic approach. A comprehensive list of HGF and MET targeted experimental therapeutics for oncology now in human clinical trials can be found here.
MET kinase inhibitors
Kinase inhibitors are low molecular weight molecules that prevent ATP binding to MET, thus inhibiting receptor transphosphorylation and recruitment of the downstream effectors. The limitations of kinase inhibitors include the facts that they only inhibit kinase-dependent MET activation, and that none of them is fully specific for MET.
- K252a (Fermentek Biotechnology) is a staurosporine analogue isolated from Nocardiopsis sp. soil fungi, and it is a potent inhibitor of all receptor tyrosine kinases (RTKs). At nanomolar concentrations, K252a inhibits both the wild type and the mutant (M1268T) MET function.
- SU11274 (SUGEN) specifically inhibits MET kinase activity and its subsequent signaling. SU11274 is also an effective inhibitor of the M1268T and H1112Y MET mutants, but not the L1213V and Y1248H mutants. SU11274 has been demonstrated to inhibit HGF-induced motility and invasion of epithelial and carcinoma cells.
- PHA-665752 (Pfizer) specifically inhibits MET kinase activity, and it has been demonstrated to represses both HGF-dependent and constitutive MET phosphorylation. Furthermore, some tumors harboring MET amplifications are highly sensitive to treatment with PHA-665752.
- ARQ197 (ArQule) is a promising selective inhibitor of MET, which entered a phase 2 clinical trial in 2008.
- Foretinib (XL880, Exelixis) targets multiple receptor tyrosine kinases (RTKs) with growth-promoting and angiogenic properties. The primary targets of foretinib are MET, VEGFR2, and KDR. Foretinib has completed a phase 2 clinical trials with indications for papillary renal cell carcinoma, gastric cancer, and head and neck cancer.
- SGX523 (SGX Pharmaceuticals) specifically inhibits MET at low nanomolar concentrations.
- MP470 (SuperGen) is a novel inhibitor of c-KIT, MET, PDGFR, Flt3, and AXL. Phase I clinical trial of MP470 had been announced in 2007.
HGF inhibitors
Since HGF is the only known ligand of MET, formation of a HGF:MET complex blocks MET biological activity. For this purpose, truncated HGF, anti-HGF neutralizing antibodies, and an uncleavable form of HGF have been utilized so far. The major limitation of HGF inhibitors is that they block only HGF-dependent MET activation.
- NK4 competes with HGF as it binds MET without inducing receptor activation, thus behaving as a full antagonist. NK4 is a molecule bearing the N-terminal hairpin and the four kringle domains of HGF. Moreover, NK4 is structurally similar to angiostatins, which is why it possesses anti-angiogenic activity.
- Neutralizing anti-HGF antibodies were initially tested in combination, and it was shown that at least three antibodies, acting on different HGF epitopes, are necessary to prevent MET tyrosine kinase activation. More recently, it has been demonstrated that fully human monoclonal antibodies can individually bind and neutralize human HGF, leading to regression of tumors in mouse models. Two anti-HGF antibodies are currently available: the humanized AV299 (AVEO), and the fully human AMG102 (Amgen).
- Uncleavable HGF is an engineered form of pro-HGF carrying a single amino-acid substitution, which prevents the maturation of the molecule. Uncleavable HGF is capable of blocking MET-induced biological responses by binding MET with high affinity and displacing mature HGF. Moreover, uncleavable HGF competes with the wild-type endogenous pro-HGF for the catalytic domain of proteases that cleave HGF precursors. Local and systemic expression of uncleavable HGF inhibits tumor growth and, more importantly, prevents metastasis.
Decoy MET
Decoy MET refers to a soluble truncated MET receptor. Decoys are able to inhibit MET activation mediated by both HGF-dependent and independent mechanisms, as decoys prevent both the ligand binding and the MET receptor homodimerization. CGEN241 (Compugen) is a decoy MET that is highly efficient in inhibiting tumor growth and preventing metastasis in animal models.
Immunotherapy targeting MET
Drugs used for immunotherapy can act either passively by enhancing the immunologic response to MET-expressing tumor cells, or actively by stimulating immune cells and altering differentiation/growth of tumor cells.
Passive immunotherapy
Administering monoclonal antibodies (mAbs) is a form of passive immunotherapy. MAbs facilitate destruction of tumor cells by complement-dependent cytotoxicity (CDC) and cell-mediated cytotoxicity (ADCC). In CDC, mAbs bind to specific antigen, leading to activation of the complement cascade, which in turn leads to formation of pores in tumor cells. In ADCC, the Fab domain of a mAb binds to a tumor antigen, and Fc domain binds to Fc receptors present on effector cells (phagocytes and NK cells), thus forming a bridge between an effector and a target cells. This induces the effector cell activation, leading to phagocytosis of the tumor cell by neutrophils and macrophages. Furthermore, NK cells release cytotoxic molecules, which lyse tumor cells.
- DN30 is monoclonal anti-MET antibody that recognizes the extracellular portion of MET. DN30 induces both shedding of the MET ectodomain as well as cleavage of the intracellular domain, which is successively degraded by proteasome machinery. As a consequence, on one side MET is inactivated, and on the other side the shed portion of extracellular MET hampers activation of other MET receptors, acting as a decoy. DN30 inhibits tumour growth and prevents metastasis in animal models.
- OA-5D5 is one-armed monoclonal anti-MET antibody that was demonstrated to inhibit orthotopic pancreatic and glioblastoma tumor growth and to improve survival in tumor xenograft models. OA-5D5 is produced as a recombinant protein in Escherichia coli. It is composed of murine variable domains for the heavy and light chains with human IgG1 constant domains. The antibody blocks HGF binding to MET in a competitive fashion.
Active immunotherapy
Active immunotherapy to MET-expressing tumors can be achieved by administering cytokines, such as interferons (IFNs) and interleukins (IL-2), which triggers non-specific stimulation of numerous immune cells. IFNs have been tested as therapies for many types of cancers and have demonstrated therapeutic benefits. IL-2 has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of renal cell carcinoma and metastatic melanoma, which often have deregulated MET activity.
See also
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Further reading
- Peruzzi B, Bottaro DP (2006). "Targeting the c-Met signaling pathway in cancer". Clin. Cancer Res. 12 (12): 3657–60. doi:10.1158/1078-0432.CCR-06-0818. PMID 16778093.
- Birchmeier C, Birchmeier W, Gherardi E, Vande Woude GF (December 2003). "Met, metastasis, motility and more". Nat. Rev. Mol. Cell Biol. 4 (12): 915–25. doi:10.1038/nrm1261. PMID 14685170.
- Zhang YW, Vande Woude GF (February 2003). "HGF/SF-met signaling in the control of branching morphogenesis and invasion". J. Cell. Biochem. 88 (2): 408–17. doi:10.1002/jcb.10358. PMID 12520544.
- Paumelle R, Tulasne D, Kherrouche Z, Plaza S, Leroy C, Reveneau S, Vandenbunder B, Fafeur V, Tulashe D, Reveneau S (April 2002). "Hepatocyte growth factor/scatter factor activates the ETS1 transcription factor by a RAS-RAF-MEK-ERK signaling pathway". Oncogene 21 (15): 2309–19. doi:10.1038/sj.onc.1205297. PMID 11948414.
- Comoglio PM (1993). "Structure, biosynthesis and biochemical properties of the HGF receptor in normal and malignant cells". EXS 65: 131–65. PMID 8380735.
- Maulik G, Shrikhande A, Kijima T, et al. (2002). "Role of the hepatocyte growth factor receptor, c-Met, in oncogenesis and potential for therapeutic inhibition". Cytokine Growth Factor Rev. 13 (1): 41–59. doi:10.1016/S1359-6101(01)00029-6. PMID 11750879.
- Ma PC, Maulik G, Christensen J, Salgia R (2004). "c-Met: structure, functions and potential for therapeutic inhibition". Cancer Metastasis Rev. 22 (4): 309–25. doi:10.1023/A:1023768811842. PMID 12884908.
- Knudsen BS, Edlund M (2004). "Prostate cancer and the met hepatocyte growth factor receptor". Adv. Cancer Res. Advances in Cancer Research 91: 31–67. doi:10.1016/S0065-230X(04)91002-0. ISBN 978-0-12-006691-9. PMID 15327888.
- Dharmawardana PG, Giubellino A, Bottaro DP (2005). "Hereditary papillary renal carcinoma type I". Curr. Mol. Med. 4 (8): 855–68. doi:10.2174/1566524043359674. PMID 15579033.
- Kemp LE, Mulloy B, Gherardi E (2006). "Signalling by HGF/SF and Met: the role of heparan sulphate co-receptors". Biochem. Soc. Trans. 34 (Pt 3): 414–7. doi:10.1042/BST0340414. PMID 16709175.
- Proto-Oncogene Proteins c-met at the US National Library of Medicine Medical Subject Headings (MeSH)
- UniProtKB/Swiss-Prot entry P08581: MET_HUMAN, ExPASy (Expert Protein Analysis System) proteomics server of the Swiss Institute of Bioinformatics (SIB)
- A table with references to significant roles of MET in cancer
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Copyright (c) Arvin S. Quist
INTRODUCTION TO CLASSIFICATION
THE NEED FOR CLASSIFICATION
A government is responsible for the survival of the nation and its people. To ensure that survival, a government must sometimes stringently control certain information that (1) gives the nation a significant advantage over adversaries or (2) prevents adversaries from having an advantage that could significantly damage the nation. Governments protect that special information by classifying it; that is, by giving it a special designation, such as "Secret," and then restricting access to it (e.g., by need-to-know requirements and physical security measures).
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MAJOR AREAS OF CLASSIFIED INFORMATION
The information that is classified by most democracies, whether in peacetime or wartime, is usually limited to information that concerns the nation's defense or its foreign relations--military and diplomatic information. Most of that information falls within five major areas: (1) military operations, (2) weapons technology, (3) diplomatic activities, (4) intelligence activities, and (5) cryptology. The latter two areas might be considered to be special parts of the first three areas. That is, intelligence and cryptology are "service" functions for the primary areas--military operations, weapons technology, and diplomatic activities. From a historical perspective, the classification of weapons technology became widespread only in the 20th century. Classification of information about military operations and diplomatic activities has been practiced for millennia.
Examples of military-operations information that is frequently classified include information concerning the strength and deployment of forces, troop movements, ship sailings, the location and timing of planned attacks, tactics and strategy, and supply logistics. Obviously, if an enemy learned the major details of an impending attack, that attack would be less successful than if it came as a surprise to the enemy.* Information possessed by a government about an adversary's military activities or capabilities must be protected to preserve the ability to predict those activities or to neutralize those capabilities. If the adversary knew that the government had this information, the adversary would change those plans or capabilities. Military-operations information is usually classified for only a limited time. After an operation is over, most of the important information is known to the enemy.
Weapons technology is classified to preserve the advantage of surprise in the first use of a new weapon,† to prevent an adversary from developing effective countermeasures against a new weapon,‡ or to prevent an adversary from using that technology against its originator (by developing a similar weapon). A major factor in that latter reason for classifying weapons technology is "lead time." Classifying advanced weapons-technology information prevents an adversary from using that information to shorten the time required to produce similar weapons systems for its own use. Consequently, assuming continued advancements in a weapons technology by the initial developer of that technology, the adversary's weapons systems will not be as effective as those of the nation that initially developed that technology, and the adversary will be at a disadvantage.
With respect to lead time, when weapons systems can be significantly improved, then information on "obsolete" weapons is much less sensitive than information on newer weapons. Thus, information on muzzle-loading rifle technology was not as sensitive as that on breech-loading rifle technology, which was not as sensitive as information on lever-action rifle technology, . . . semiautomatic rifle . . . automatic rifle . . . machine gun. However, with respect to nuclear weapons, a "rogue" nation or terrorist group can probably achieve its objectives just as easily with "crude" kiloton nuclear weapons that might require a ship or truck to transport as with sophisticated megaton nuclear weapons that might fit into a (large) suitcase. Thus, "obsolete" nuclear-weapons technology should be continue to be protected, especially with respect to technologies concerning production of highly enriched uranium or other nuclear-weapon materials.
Weapons technology includes scientific and technical information related to that technology. World War I marked the start of the "modern" period when science and technology affected the development of weapons systems to a greater degree than any time previously. That interrelationship became even more pronounced in World War II, with notable scientific and technological successes: the atomic bomb, radar, and the proximity fuse. World War II, particularly with respect to the atomic bomb, marked the first time that the progress of military technology was significantly influenced by scientists, as contrasted to advances by engineers or by scientists working as engineers.
With respect to classification, the more that applied scientific or technical information is uniquely applicable to weapons, the more likely that this information will be classified. Generally, basic research is not classified unless it represents a major breakthrough leading to a completely new weapons system. An example of that circumstance was the rigid classification during World War II, and for several years thereafter, of much basic scientific research related to atomic energy (nuclear weapons).
The need for secrecy in diplomatic negotiations and relations has long been recognized. A nation's ability to obtain favorable terms in negotiations with other countries would be diminished if its negotiating strategy and goals were known in advance to the other countries.* The effectiveness of military-assistance agreements between nations would be impaired if an adversary knew of them and could plan to neutralize them. In New York Times v. United States, the "Pentagon Papers" case, U.S. Supreme Court Justice Stewart recognized the importance of secrecy in foreign policy and national defense matters:
It is elementary that the successful conduct of international diplomacy and the maintenance of an effective national defense requires both confidentiality and secrecy. Other nations can hardly deal with this Nation in an atmosphere of mutual trust unless they know that their confidences will be kept . . .. In the area of basic national defense the frequent need for absolute secrecy is, of course, self evident.
During the term of the first
president, it was established that some need for secrecy in diplomatic matters would remain even after negotiations were completed. President Washington, in 1796, refused a request by the House of Representatives for documents prepared for treaty negotiations with U.S. and gave the following as one reason for refusal: England
The nature of foreign negotiations requires caution, and their success must often depend on secrecy; and even when brought to a conclusion a full disclosure of all the measures, demands, or eventual concessions which may have been proposed or contemplated would be extremely impolitic; for this might have a pernicious influence on future negotiations, or produce immediate inconvenience, perhaps danger and mischief, in relation to other powers.
It has been said that President Nixon initially was not going to attempt to stop the New York Times and other newspapers from publishing the "Pentagon Papers." However, the executive branch was then in secret diplomatic negotiations with
, and Henry Kissinger "is said to have persuaded the president that the Chinese wouldn't continue their secret parleys if they saw that China couldn't keep its secrets." Washington
Intelligence information includes information gathering and covert operations. Collecting military and diplomatic information about other nations involves the use of photoreconnaissance airplanes and satellites, communication intercepts, the review of documents obtained openly, and other overt methods. However, information gathering also includes the use of undercover agents, confidential sources, and other covert methods. For those covert activities, secrecy is usually imposed on the identity of agents or sources, on information about intelligence methods and capabilities, and on much of the information received from the covert sources. Few clandestine agents could be recruited (or, in some instances, would live long) if their identity were not a closely guarded secret. Information provided by a clandestine agent must frequently be classified because, if a government knew that some of its information was compromised, it might be able to determine the identity of the person (agent) who provided the information to its adversary. Successful intelligence-gathering methods must be protected so that the adversary does not know the degree of their success and is not stimulated to develop countermeasures to stop the flow of information. Intelligence information from friendly nations is generally classified by the recipient country. Allies would be less willing to share intelligence information if they knew that it would not be protected against disclosure.
Cryptology encompasses methods to code and transmit secret messages and methods to intercept and decode messages. Writing messages in code, or cryptography,* has been practiced for thousands of years. One of the earliest preserved texts of a coded message is an inscription carved on an Egyptian tomb in about 1900 B.C. The earliest known pottery glaze formula was written in code on a Mesopotamian cuneiform tablet in about 1500 B.C. The Spartans established a system of military cryptography by the 5th century B.C. Persia later used cryptography for political purposes. Cryptography began its steady development in western civilization starting about the 13th century, primarily in
. By the early 16th century, Italy 's ruling Council of Ten had an elaborate organization for enciphering and deciphering messages. Venice
Restrictions on cryptologic information are necessary to protect
communications. Diplomatic negotiations could not successfully be conducted at locations other than the seat of government if safe communications could not be established. Cryptologic information must also be protected to prevent an adversary from learning of a nation's capabilities to intercept and decode messages. If an adversary learns that its communications are not secure, it will use another method, which will require additional time and effort to defeat.[‡] The Allies' World War II success in breaking the German codes contributed to shortening that war. That success was kept secret until 1974, about 34 years after the German code had been broken and about 29 years after World War II had ended. The U.S. Army's success in breaking a World War II U.S.S.R. code (the Venona project, which began in 1943 and continued until 1980) was not made public until about 1995. That was about 50 years after the first such message had been deciphered (and about 45 years after the U.S.S.R. had learned through espionage of the Army's success). U.S.
BASIS FOR CLASSIFICATION IN THE UNITED STATES
The need for governmental secrecy was directly recognized in the U.S. Constitution. Article I, Sect. 5, of the Constitution explicitly authorizes secrecy in government by stating that "Each House shall keep a Journal of its Proceedings, and from time to time publish the same, excepting such Parts as in their Judgment require Secrecy." Also included in the Constitution, in Article I, Sect. 9, is a statement that "a regular Statement and Account of the Receipts and Expenditures of all public Money shall be published from time to time." A U.S. Court of Appeals has determined that the phrase "from time to time" was intended to authorize expenditures for certain military or foreign relations matters that were intended to be kept secret for a time.
The Constitution does not explicitly provide for secrecy by the Executive Branch of the U.S. Government. However, the authority of that Executive Branch to keep certain information secret from most
citizens is implicit in its executive responsibilities, which include the national defense and foreign relations. This presidential authority has been upheld by the Supreme Court in a number of cases. Judicial decisions have also relied on a common-law privilege for a government to withhold information concerning national defense and foreign relations. Congress, by two statutes, the Freedom of Information Act and the Internal Security Act of 1950, has implicitly recognized the president's authority to classify information (see Chapter 3). U.S.
At this time in the
, information is classified either by presidential authority, currently Executive Order 12958, or by statute, the Atomic Energy Act of 1954, as amended (Atomic Energy Act). Classification under Executive Orders and under the Atomic Energy Act is extensively discussed in Chapters 3 and 4, respectively. United States
CLASSIFICATION AND SECURITY
Classification has been variously described as the "cornerstone" of national security, the "mother" of security, and the "kingpin" of an information security system.,,, Classification identifies the information that must be protected against unauthorized disclosure. Security determines how to protect information after it is classified. Security includes both personnel security and physical security.
The initial classification determination, establishing what should not be disclosed to adversaries and the level of protection required, is probably the most important single factor in the security of all classified projects and programs., None of the expensive personnel-clearance and information-control provisions (physical security aspects) of an information security system comes into effect until information has been classified; classification is the pivot on which the whole subsequent security system turns (excluding security for other reasons, such as to prevent theft of materials). 19 Therefore, it is important to classify only information that truly warrants protection in the interest of national security.
Since the mid 1970s, several classification experts have remarked on the increasing emphasis by some government agencies on physical-security matters, which has been accompanied by a decreased emphasis on the classification function. One of the founders (and the first chairman) of the National Classification Management Society (NCMS), who was also an Atomic Energy Commission Contractor Classification Officer, has expressed concern about the tendency to emphasize the word "security" at the expense of the word "classification" with respect to security classification of information.17 In the mid 1980s another charter member of the NCMS pointed out that, although the status of classification still remained high in the Department of Energy (DOE), the situation had changed within the Department of Defense, where Classification Management had been organizationally placed under Security. Even the NCMS, founded as a classification organization, appears to be changing to become increasingly oriented towards security matters rather than classification matters. It is noteworthy that the marked emphasis by the U.S. Government in recent years on physical-security measures has not been accompanied by any significant increased emphasis on classification matters.
The previous paragraph was written in 1989, and the trend described in that paragraph has continued. The classification function at DOE headquarters is now a part of the security organization as is the classification function at many DOE operations offices and DOE-contractor organizations. That function generally used to be part of a technical or other non-security organization. The NCMS has also continued to become more security-oriented.
With respect to classification as a profession (or lack of recognition thereof), it is interesting to note some comments and a recommendation in the Report of the Commission on Protecting and Reducing Government Secrecy. In this 1997 report, that Commission noted the "all-important initial decision of whether to classify at all," and that "this first step of the classification management process . . . tends to be the weakest link in the process of identifying, marking, and then protecting the information." The Commission further stated that "the importance of the initial decision to classify cannot be overstated." However, the Commission then stated that "classification and declassification policy and oversight . . . should be viewed primarily as information management issues which require personnel with subject matter and records management expertise." Although recommending that "The Federal Government . . . [should] create, support, and promote an information systems security career field within the Government," the Commission made no similar recommendation for security classification of information as a profession or career. Res ipsa loquitur.
[*] "When a nation is at war many things that might be said in time of peace are such a hindrance to its effort that their utterance will not be endured so long as men fight and that no Court could regard them as protected by any constitutional right" [Schenck v. United States, 249 U.S. 47, 52 (1919) (J. Holmes)].
[†] Since the September 11, 2001, terrorist attacks against the World Trade Center towers and the Pentagon, the United States considers itself to be in a war against terrorism. One consequence has been a significant shift in opinion, not only of the general public but also of some strong supporters of freedom-of-information matters, towards favoring more control of information that might aid terrorists. This increased control, especially pertaining to weapons of mass destruction, includes (1) establishing broader criteria for identifying information that is classified or "sensitive"; (2) permitting reclassification of declassified information, and (3) restricting further governmental distribution of documents already released to the public.
*However, during the Greek and Roman eras in the Mediterranean, when the infantry was paramount and both sides were approximately equally equipped with respect to weapons, many battles were fought without attempts to maintain secrecy of troop movements or with respect to surprise attacks (B. and F. M. Brodie, From Crossbow to H-Bomb, Indiana University Press, Bloomington, Ind., 1973, p. 17).
†"Secret" weapons have proven decisive in warfare. One example of the decisive impact of a new weapon was at the battle of Crecy in 1346. At this battle, the English used their "secret" weapon, the longbow, to defeat the French decisively. Although the French had a two-to-one superiority in numbers (about 40,000 to 20,000), the French lost about 11,500 men, while the English lost only about 100 men (W. S. Churchill, A History of the English-Speaking Peoples, Vol. 1, Dodd, Mead and Co., New York, 1961, pp. 332-351; B. and F. M. Brodie, From Crossbow to H-Bomb, Indiana University Press, Bloomington, Ind., 1973, pp. 37-40).
‡In World War II, the Germans developed an acoustic torpedo designed to home in on a ship's propellers. However, the Allies obtained advance information about this torpedo so that when it was first used by the Germans, countermeasures were already in place (B. and F. M. Brodie, From Crossbows to H-Bombs, Indiana University Press, Bloomington, Ind., 1973, p. 222).
*In 1921, the United States, Britain, France, Italy, and Japan held a conference to limit their naval armaments. The United States had broken Japan's diplomatic code and thereby knew the lowest naval armaments that Japan would accept. Therefore, U.S. negotiators had merely to wait out Japan's negotiators to reach terms favorable to the United States (J. Bamford, The Puzzle Palace, Houghton, Mifflin Co., Boston, 1982, pp. 9-10).
*The breaking of codes is termed cryptanalysis.
[‡] Even "friendly" nations get upset if they know that one of their codes has been broken. As noted earlier in this chapter, the United States deciphered Japan's diplomatic code in 1921. Herbert O. Yardley, who was principally responsible for breaking this code, wrote a book, The American Black Chamber, published in 1931, which included information on this matter. Yardley's book did not contribute to developing friendly United States-Japanese relations. A consequence of this revelation was enactment of a U.S. statute that made it a crime for anyone who, by virtue of his employment by the United States, obtained access to a diplomatic code or a message in such code and published or furnished to another such code or message, "or any matter which was obtained while in the process of transmission between any foreign government and its diplomatic mission in the United States" (48 Stat. 122, June 10, 1933, codified at 18 U.S.C. Sect. 952.)
B. and F. M. Brodie, From Crossbow to H-Bomb, Indiana University Press, Bloomington, Ind., 1973, p. 172. Hereafter this book is cited as "Brodie."
Brodie, p. 233.
New York Times v. United States, 403 U.S. 713, 728 (1971).
J. D. Richardson, A Compilation of Messages and Papers of the Presidents. 1789-1897, U.S. Government Printing Office, Washington, D.C., Vol. I, at 194-195 (1896).
Richard Gid Powers, "Introduction," in Secrecy--The American Experience, by Daniel Patrick Moynihan, Yale University Press, New Haven, Conn., 1998, p. 32.
D. Kahn, The Codebreakers, MacMillan, Inc., New York, 1967, p. 71. Hereafter cited as "Kahn."
Kahn, p. 75.
Kahn, p. 82.
Kahn, p. 86.
Kahn, p. 106.
Kahn, p. 109.
See, for example, F. W. Winterbotham, The Ultra Secret, Harper & Row, New York, 1974.
Halperin v. CIA, 629 F.2d 144, 154-162 (D.C. Cir., 1980).
U.S. Constitution, Article II, sect. 2.
See, for example, Totten v. United States, 92 U.S. 105 (1875); United States v. Reynolds, 345 U.S. 1 (1952); Weinberger v. Catholic Action of Hawaii, 454 U.S. 139 (1981).
F. E. Rourke, Secrecy and Publicity: Dilemmas of Democracy, Johns Hopkins Press, Baltimore, 1961, pp. 63-64.
D. B. Woodbridge, "Footnotes," J. Natl. Class. Mgmt. Soc. 12 (2), 120-124 (1977), p.122.
R. J. Boberg, "Panel--Classification Management Today," J. Natl. Class. Mgmt. Soc. 5 (2), 56-60 (1969), p. 57.
E. J. Suto, "History of Classification," J. Natl. Class. Mgmt. Soc. 12 (1), 9-17 (1976), p.13.
James J. Bagley, "NCMS - Now and the Future," J. Natl. Class. Mgmt. Soc. 25, 20-29 (1989), p. 28.
T. S. Church, "Panel--Science and Technology, and Classification Management," J. Natl. Class. Mgmt. Soc. 2, 39-45 (1966), p. 40.
W. N. Thompson, "Security Classification Management Coordination Between Industry and DOD," J. Natl. Class. Mgmt. Soc. 4 (2), 121-128 (1969), p. 121.
W. N. Thompson, "User Agency Security Classification Management and Program Security," J. Natl. Class. Mgmt. Soc. 8, 52-53 (1972), p. 52.
Department of Defense Handbook for Writing Security Classification Guidance, DoD 5200.1-H, U.S. Department of Defense, Mar. 1986, p. 1-1.
F. J. Daigle, "Woodbridge Award Acceptance Remarks," J. Natl. Class. Mgmt. Soc. 21, 110-112 (1985), p. 111.
D. C. Richardson, "Management or Enforcement," J. Natl. Class. Mgmt. Soc. 23, 13-20 (1987).
Report of the Commission on Protecting and Reducing Government Secrecy, S. Doc. 105-2, Daniel Patrick Moynihan, Chairman; Larry Combest, Vice Chairman, Commission on Protecting and Reducing Government Secrecy, U.S. Government Printing Office, Washington, D.C., 1997. Hereafter cited as the "Moynihan Report."
Moynihan Report, p. 19.
Moynihan Report, p. 35.
Moynihan Report, p. 44.
Moynihan Report, p. 111.
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