In vivo metabolism of fruity carboxylic esters in the human oral cavity is partly driven by microbial enzymes

Food flavor perception is shaped by biochemical events during oral processing, with oral metabolism remaining poorly understood. This study investigated the oral fate of fruity carboxylic esters and its relationship with salivary and microbiological parameters. Participants (n = 101) rinsed their mouths with either water (control) or an ester-containing solution for 30 s. Esters and their corresponding acids were analyzed by gas chromatography-mass spectrometry before and after rinsing. Results showed a significant decrease in ester and a marked increase in acid levels, indicating rapid metabolic conversion. Ester recovery was associated with the physicochemical properties of the compounds, participants' body mass index, and salivary esterase activity (SEAC). SEAC also correlated with oral microbiota composition and the abundance of microbial genes encoding carboxylic ester hydrolases, as assessed by shotgun metagenomics. These findings provide the first evidence of rapid ester metabolism in the human mouth and its relationship with the salivary microbiome.