Pectin extracted from by-products of processing of vegetables like butternut and beetroot show promise for stabilizing emulsions and could offer interesting new ingredients for emulsion-based foods.
Researchers from Argentina and Wales report that pectin from both butternut (Cucumis moschata Duch. ex Poiret) and beetroot (Beta vulgaris L. var. conditiva) were able to stabilize food emulsions for 30 days with the “oil-water interface are rich in protein and/or polyphenols”.
Extracted pectin (E440) with worldwide production estimated at 35,000 tonnes a year, is currently widely used as gelling agents in jams, confectionary, and bakery fillings, and stabilisers in yoghurts and milk drinks.
“The object of this research work was to study the potential of butternut and beetroot pectins for use as additives in the food industry,” wrote the researchers in Food Hydrocolloids .
“The extraction process of the pectins involved the use of non-pectolytic enzymes such as cellulases, an environmentally friendly alternative to the industrial pectin extraction through hot mineral acids.”
The enzymatic extraction process produced butternut pectin with a high degree of methyl esterification, while hand beetroot pectin had a low degree of methyl esterification.
The chemical structure of pectin is based on a chain of repeating galacturonic acid units. In very basic terms, galacturonic acid has a ring structure with a carboxyl (CO2-) group jutting out. In nature, a large portion of these carboxyl groups have methanol (CH3OH) bonded via a reaction called esterification.
A high degree of esterification, or many bonded methanol groups, produces a high methoxyl (HM) pectin, while a low degree of esterification gives a low methoxyl (LM) pectin.
The butternut pectin for a viscous solution rather than a gel, said the researchers, while beetroot pectin formed gels with addition of calcium ions.
“The surface tension of butternut pectin was similar to that reported for citrus pectin while the surface tension for beetroot pectin was lower and similar to that of sugar beet pectin,” said the researchers.
“Both pectins were able to stabilize oil in water emulsions over a 30 day period and it is apparent that the fractions adsorbed at the oil-water interface are rich in protein and/or polyphenols.
“Pectins recovered as by-products of vegetable processing, therefore, seem to be promising materials as food additives.”
The researchers were affiliated with the City University, Buenos Aires, the National Scientific and Technical Research Council of Argentina (CONICET), and the Centre for Water Soluble Polymers at the Glyndŵr University Wrexham.
Source: Food Hydrocolloids
Published online ahead of print, doi: 10.1016/j.foodhyd.2012.10.012
“Butternut and beetroot pectins: Characterization and functional properties”
Authors: E.N. Fissore, A.M. Rojas, L.N. Gerschenson, P.A. Williams