The Role of Saliva in Food Sensory Perception: Relevant Knowledge to Design Healthy Foods

Abstract

Food choices and consumption are determined by a range of factors that contribute to aversion or pleasure and guide to final intake. Among these, the sensorial characteristics of food have a major and decisive role in choice behaviour. Although some of the mechanisms involved in oral food perception, namely in taste and astringency perception, are considerable known, many questions remains, particularly in what concerns variations among individuals in their sensitivity for food sensorial aspects. The understanding of the mechanisms leading to different responses for the same sensorial stimulus is particularly important to understand food choices. Bitter has been the basic taste most studied for variations among individuals in perception and in how this influences food behaviour and nutritional status. The observation, at several years ago, that some individuals are very sensitive to the bitterness of the compounds phenyl thiocarbamide (PTC) or 6-n-propylthyouracil (PROP), whereas others are almost insensitive, triggered the emergence of diverse studies about the motif for that, resulting in the identification of gene polymorphisms for the bitter taste receptor TAS2R38. Subsequently to that, polymorphisms for other receptors and taste qualities have been identified. Even so, these genetic variations are not able to explain the total diversity in taste/oral sensations responses. In recent years, it has begun to become apparent that saliva has a relevant role in taste recognition mechanisms. Apart from astringency, which is well known to depend on salivary proteins to develop and being perceived, basic tastes started to be related with saliva composition. Some salivary proteins, among which carbonic anhydrase VI, cystatins, amylase and others, have been observed to relate with taste perception. However, saliva secretion changes with taste stimulation and according dietary habits. Moreover, body weight condition, metabolic status or diverse pathologies are responsible for changes in saliva composition. Being this fluid important in modulating oral food perception, to know individuals’ saliva composition becomes of interest for modulating or directing choices. Based on the literature and recent scientific results, the role of saliva in food sensory perception will be discussed according to these two angles. The question of the high between-subject variability in view of saliva properties and its consequence on perception will be emphasized.