Flavour as a psychological construct: implications for perceiving and measuring the sensory qualities of foods

While flavours comprised of simple taste/odour combinations can be easily decomposed, there is evidence that the individual components are seldom perceived independently. Manifestations of interactions include smell/taste confusions, attribution of taste properties such as sweetness or sourness to odours, and the enhancement and suppression of tastes by such odours. These phenomena are probably the result of blurring of the perceptual boundaries of odour and taste properties during repeated pairings as flavours. Following such pairings in the laboratory, odours can be shown to increase in perceived taste properties. It is proposed that during flavour formation, the components are encoded in memory in such a way that a later odour stimulus also elicits taste properties. Sensory properties such as sweetness can thus be seen as cognitive phenomena associated with both tastes and odours, in the latter case residing in memory. However, unlike some odour combinations, flavours, although usually perceived as a functional whole, are not indivisible synthetic entities. Perceptual interactions between odours and tastes are dependent on the extent to which an analytical approach is taken to the measurement of flavour qualities. Thus, odour enhancement of sucrose sweetness is not observed when the intensities of all the components in a flavour are rated. This has been interpreted as a consequence of rating strategies. However, the data are more consistent with a perceptual/cognitive interpretation. Recent research from our lab has shown that the cognitive strategy employed during the pairing of odours and tastes will also determine whether taste/odour interactions occur. The question of how to measure flavour properties is raised by these findings. Whether panellists focus on the sensory source of, for example, sweetness will depend upon the perceptual strategy they adopt. Asking panellists to focus only on the taste sweetness, while possible, may be assuming that odour and taste properties are independent within foods.