Variability of human saliva composition: possible relationships with fat perception and liking

Saliva is the medium that bathes the taste receptors in the oral cavity and in which aroma and taste compounds are released when food is eaten. Moreover saliva contains enzymes and molecules that can interact with food. To date, little research has been devoted to the intra- and inter-individual variabilities of these components and their inter-relationships. The first aim of this work was to study intra- and inter-individual variabilities over time in the composition of molecules likely to interact with food in the mouth, with particular focus on molecules that might interact with fat. The second aim was to try to relate this composition to a liking for fat and its perception. Stimulated and unstimulated saliva from 13 subjects was collected in the morning and afternoon on three occasions at 4-month intervals. Saliva characteristics such as flow, protein concentration, lipolysis, proteolysis, amylolysis, lipocalin concentration, lysozyme activity, total antioxidant status and uric acid concentrations were measured, as well as the liking for and perceived fattiness of a fat solution. The results showed that for most of the measured characteristics, intra-subject variability in saliva composition was smaller than inter-subject variability, with remarkable stability over time (8 months) in terms of flow, lypolysis, proteolysis and total antioxidant status. Relationships were found between some of these characteristics (lipolysis, lipocalin and flow) and fat-liking or perception, showing that the composition of saliva may play an important role in fat perception and liking.