From masking the ?beany? flavour in soy products to taking the bitter edge off the alkaloids of herbal preparations, modulating the taste of substances to within acceptable consumer limits can lead to strong sales of an otherwise marginally acceptable product. George A Burdock, PhD, explains.
The art and science of sensory deception is most often thought of in terms of perfumes to mask objectionable odours. However, sensory deception in foods is at least as old and was the driving force for the spice trade during the Middle Ages, at a time when refrigeration was unavailable. Pungent spices such as clove, pepper, cardamom, fennel and cinnamon were used to make otherwise stale or spoiled meat and other foods more palatable. Coincidentally, many of these spices also had antibacterial effects and acted as early preservatives, so their use was not always simply cosmetic.
Today, regulations prohibit the sale to the public of spoiled, putrid or unfit food. However, sensory deception still exists and has evolved to become an essential contributor to the production of foods, drugs and dietary supplements. Uses include addition of substances to prevent warmed-over-flavour in cooked and refrigerated meats, to mask the ?beany? flavour in soy products, take the bitter edge off the alkaloids of herbal preparations and make oral medicines more ?child-friendly? (See Table 1).
As noted above, the first attempts at sensory deception consisted of adding spices to mask an unpleasant flavour or taste. But, with penetrating adverse tastes, the further addition of spices soon reached the point of diminishing returns—either the cost of the spices itself contributed too much to the cost of the product or the flavour of the spices became overwhelming. It is at this point where flavour modification becomes important.
Flavour modifiers and sensory deceivers
With a few exceptions (such as vinegar or salt), a flavour is actually the sum of many contributing elements, some of which are perceived as ?stronger? than others. Flavour modification is the art of changing an existing taste by enhancing or suppressing one or more of its components. For example, the use of ?coolant flavours?, while having little or no taste of their own, stimulate cold receptors in the mouth to make the experience of a menthol-flavoured candy more intense.
On the other hand, sweeteners, such as aspartame or even glycyrrhizin (an extract of liquorice root), can be used at levels below the perception of sweetness to enhance other more costly flavour ingredients. Similarly, low levels of artificial sweeteners can also be used to strengthen other flavours naturally present in cereals, nutrition bars, nutraceuticals and sports nutrition products, making them more enticing. Conversely, thaumatin (an extract of the African katemfe fruit) can be used to abolish the bitterness of a substance and allow naturally present sweeteners to be perceived (See Table 2).
Umami (pronounced oo-MOM-ee) is the fifth and most recently recognised of the basic taste sensations (in addition to sweet, sour, salty and bitter that we all learned about in primary school). Umami was first recognised by the Japanese and is the basis for their addition of certain seaweeds to soup. These seaweeds contain the amino acid glutamate, which as the sodium salt (monosodium glutamate or MSG) became known as a potent flavour enhancer for meats and savoury flavours. Whilst MSG has no flavour of its own, the enhancing properties add savoury flavour to meat products, making even inexpensive cuts of meat taste ?delicious.? Unfortunately, MSG received considerable adverse publicity as the culprit responsible for ?Chinese restaurant syndrome,? where the faces of people metabolically intolerant to MSG would turn bright red. As a result, it has been largely replaced by autolysed yeast, tomato products, mushrooms and other foods, all of which contain naturally high levels of glutamates and are more label-friendly.
On the other hand, strawberries contain more citric acid than malic and the former is therefore more acceptable for addition to a strawberry flavour. Conversely, the addition of miraculin (an extract of miracle fruit) can convert a highly acidic (i.e. sour) taste of a fruit to a sweet taste.
Dietary supplements, with the heavy emphasis on added vitamins or soy products, present some special problems. Strong flavourants such as mint, or cooling or spicy notes, will not totally cover the objectionable ?raw/green? or ?beany? taste of soy products and may impart a flavour that is not expected and therefore not acceptable to the consumer. In this circumstance, it might be possible to mask the soy taste with chocolate or fruit flavours. Most often, soy products are modified with vanilla flavours to re-orient the perception of the consumer to a bland/creamy taste.
Some tastes are not solely mouth-derived, but may have a strong fragrance component, such as peach. Some ?tastes? are not tastes at all, but ?mouth feel? such as the fatty or creamy taste of butter or ice cream, the bite of mustard, horseradish or black pepper and the heat of chili peppers.
There is also mounting evidence that taste receptors are also present in the gut, kidney and brain, and provide us with more feedback on what we should eat and how much. Sweet tastes and fatty tastes may well be a signal of calorie-rich food and an evolutionarily developed signal to eat more; this signal may be part of the reason for the new epidemic of obesity.
Taste sensitivity can also change. Loss of the sense of smell (as when being sick with a cold) can make food taste bland or even permit eating a raw onion, when this would normally be overwhelming and unthinkable. Many elderly persons gradually lose their sense of taste, and thus appetite. This may contribute to the weight loss seen routinely in patients in rest homes. Taste sensitivity can also be heightened. For instance, recent studies have shown that the threshold for activation of sodium-sensitive taste receptors (i.e., salty receptors) in the mouth is lowered in people on low-sodium diets.
Not all flavours can be made acceptable. An aversion to some flavours, such as bitterness, may have a strong, evolutionarily developed component as protection against eating poisonous plants, whereas a sour taste may be warning us away from unripe or rotten fruits or fermented substances. It may well be that we can never acclimate to some flavours or odours (rotten eggs, burnt hair, vomit) and their eradication in a consumable by masking may be technologically impossible. The impossible flavours are a small minority, however, and those flavours that cannot be masked might lend themselves to sensory deception through enhancement of collateral flavour attributes. After all, skatole, the chemical producing the primary odour note in human faeces, is a valuable addition at lower concentrations to the taste of vanilla ice cream.
The extent and ability of individuals to taste substances vary with their genetic makeup, state of health, metabolism, age, cultural exposure and habits determined at an early age. Yet there is a broad spectrum of acceptable flavours, combinations and intensities that will gain a favourable response from a large segment of the population. The science and art of sensory deception can serve as the key to modulating the taste of substances to within acceptable boundaries of most consumers and lead to strong sales of an otherwise marginally acceptable product.
George A Burdock, PhD, is principal of the Burdock Group, an internationally recognised authority on safety of food ingredients, personal care products and botanical/herbal supplements. He is the author of Fenaroli?s Handbook of Flavor Ingredients, Fourth Edition. The Group specialises in services encompassing strategic planning and regulatory compliance for agency-regulated products.
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