Inter-individual differences in human saliva composition affect the partition of food and beverages aroma compounds

Saliva is the first biological fluid in contact with food during consumption. As such, it might exert an important role on the release of volatile compounds from foods into the oral cavity. Thus, understanding this role could help to explain aroma perception, food preferences and dietary intake in human. To date, most of the studies performed on the field have employed compositionally simple artificial salivas or pools mixing human salivas from different individuals. Nevertheless, the whole complexity of human saliva and the effect of interindividual differences on aroma release remains underexplored. Therefore, there is a need to gain a better understanding of the effect of human saliva composition on important food and beverages aroma compounds.The first objective of this work was to optimise and validate a static HS-GC method to measure volatile partitioning from aqueous solutions. This method was adapted to microvolumes, as the collection of suitable amounts of human saliva for experimental purposes is tedious, unpleasant and sometimes (e.g hyposalivation) very difficult. Then, the HS-GC methodology was applied to a wide range of aroma compounds in presence or absence of a food matrix component (epigallocatechin-3-gallate gallate « EgCG »). Each volatile compound assayed was analysed in presence of individual human salivas submitted or not to a centrifugation process (n=6). Control samples (with water) were used to better understand the different mechanisms that saliva might induce on the partition of aroma compounds.Results showed that human saliva exerts a significant effect on the partition of volatile compounds through different mechanisms: it appears that some aroma compounds are affected by interactions with organic or inorganic salivary constituents, while others undergo enzymatic degradation (e.g. diketones). The observed effects were both compound-dependent and individual-dependent. We also found differences between saliva samples from the same individual submitted or not to a centrifugation process. Centrifugation tends to standardize the samples and to underestimate the saliva effect. Moreover, the addition of EgCG boosts the differences observed on the volatile partitioning among individuals. These results show the importance of considering interindividual differences on human saliva composition to better understand food flavour perception