Flavour is an important component of food as it affects the food choices made by the individual. The food industry is well aware of the power of flavours, as it uses them to encourage the consumption of their products. In particular, humans are drawn to salty and sweet tasting foods, while bitter foods are usually less palatable. Flavour enhancement is successful at increasing the profits of the food companies, but this can often be to the detriment of the health of the individual. This relates to the low quality of many foods that are given addictive and desirable flavours. Obesity is conditional on consumption of too many of these low quality foods, many of which have no nutritional value other than providing energy. The chemical composition of such foods, may contribute significantly to weight gain, and by deliberately enhancing their desirability the food industry is directly responsible for causing the obesity epidemic that is currently engulfing the developed nations of Western Europe, North America and Australasia.
The sensation of taste begins when taste receptors (colloquially called buds) in the mouth interact with particular food components. Tastes can be divided into a number of groups depending on the type of receptor that they interact with. Salt, sweet, bitter and sour are the modern categories of taste, but older classifications were more complex and included sweet, sour, sharp, salty, bitter, fatty, insipid, astringent, viscous, aqueous and nauseous. These older categories address the blurring of the edges of the four main categories that can occur through activation of a mixture of receptor subtypes. The difficulty with identifying flavours has been highlighted by the inability to place certain tastes such as ‘minty’ within the known categories of taste perception. In this regard the older more detailed classifications, while based on a lower understanding of molecular mechanisms, may be superior with regard the description of overall feeling associated with the flavour of foods. For this reason older classifications are often still used.
Taste then is a perception that depends on the interpretation of signals sent from taste receptors in the mouth, and this interpretation of the taste occurs following transmission of the taste to the brain. However, the flavours of foods can interact at the receptor level and alter the tastes perceived by the brain. The importance of receptor level taste perception can be demonstrated through observations that occur to taste following consumption of the Miracle Berry (Synsepalum dulcificum). The flesh of the berry contains a glycoprotein called miraculin, and this binds to the sweet receptors on the tongue. This process results in sour foods becoming sweet. This is likely possible because of the wide variation in chemical structure of sweet foods. Another compound malonate, is not in itself sweet, is added to foods such as soft drinks and baked goods because it enhances the sweet taste of the foods. Sodium glutamate tends to enhance the tastes of meats and soups and is used in these foods for this reason.
Sourness is usually considered a function of acidity, but evidence suggests that the acidity of food has no correlation with sourness. In fact, it could be argued that both bitter and sour tastes are the opposite of sweet, despite sour and bitter foods having quite distinct tastes. The strange taste characteristics of chemicals is highlighted by examples of similar chemicals. For example, certain isomers of particular chemicals have very different tastes. L-tryptophan has a bitter taste for example, whereas D-tryptophan, its stereo isomer, is 35 times sweeter than sucrose. However, the stereoisomers of tryptophan and tyrosine taste similar. Little is known about how animals perceive taste, as it is impossible to ask them. However, animal experiments have been performed on food preferences and this preference can be alters as with humans. For example, the desire for sweet foods experienced by many insects can be blocked chemically to prevent them seeking and consuming sweet foods.
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