The primer, which appears in this week's edition of Current Biology, gives a round up of recent advances in taste perception knowledge. Authors Paul Breslin and Alan Spector (of Monell Chemical Senses Center and Florida State University respectively) say there are five generally accepted taste qualities that are associated with different classes of compounds (although some animals may possess more or less). These are:
- Sweet - associated with simple carbohydrates (sugar)
- Umami (savoury) - generated by amino acids and small peptides
- Salty - associated with sodium and other ions
- Sour - generated by acids
- Bitter - stimulated by potential toxins, like plant alkaloids
Compounds are first organised into perceptual classes by the taste receptor cells, which, when activated, stimulate taste bud cells and the neural fibres connected to them. These are then channelled through the brain in substrates of perceptual and behavioural substrates. However, the authors say that the quality of taste cannot, by and large, be dissociated from hedonistic properties. "This raises the question: what adaptive function does a taste quality serve," wrote Breslin and Spector. They hazard that they answer may be in allowing the identification of chemical stimuli that serve as clues for the consequences of digestion. "Thus, the identification of taste stimuli by their perceived quality allows an animal's choices among various nutrients and toxins to be moulded by experience." In their conclusion, the authors note that what an animal digests both in the short-term and over a life-time has consequences for their very survival. So critical is taste in this respect that humans who lose their sense of taste, such as after radiotherapy, often will not eat. "Thus, while we may tend to take the sense of taste for granted relative to our other sensory modalities, its significance for health and quality of life should not be trivialised." Advances in understanding how humans detect different tastes is of crucial importance to the food industry, since it is a basic precept of product development and marketing that products that do not have the expected taste will not be well received by consumers. This is particularly pertinent when it comes to reformulation of products, to reduce salt or fat content for instance. These nutrients often have an impact on taste, and when they are reduced or removed the sensory attributes need somehow to be replaced. Source: Current Biology Vol 18, No 4, February 26 2008 Title: 'Primer: Mammalian taste perception' Authors: Paul Breslin, Alan Spector