Matrix effects of tartaric acid on the volatile release and aroma perception of fruity esters in wine

Fruity esters showed structure-dependent, non-linear responses to tartaric acid. • Gas–liquid partitioning broadly matched odor-threshold changes. • 1 H NMR supported non-covalent interactions between tartaric acid and esters. • Aromatic esters showed the strongest hydrophobic interactions with tartaric acid. • Medium-chain esters formed the strongest hydrogen bonds with tartaric acid. To investigate the matrix effects of tartaric acid on the release and sensory perception of fruity esters in wine, nine esters covering short-chain, branched-chain, medium-chain, and aromatic esters were evaluated in a model wine system containing 0–8 g/L tartaric acid. S-curve fitting, phase ratio variation, 1 H NMR spectroscopy, and quantum chemical calculations were combined to characterize these matrix effects. Results showed that branched-chain, short-chain, and aromatic esters generally exhibited an initial decrease followed by an increase in threshold as tartaric acid concentration increased. Branched-chain esters were most readily perceived at 2 g/L, with isoamyl acetate reaching a minimum threshold of 2.57 μg/L, whereas short-chain and aromatic esters showed the strongest perception at 4 g/L, with the threshold of ethyl butanoate decreasing from 37.12 to 5.16 μg/L. In contrast, medium-chain ester thresholds generally increased after tartaric acid addition. Gas–liquid partition coefficients broadly followed the threshold trends, with the kᵢ × 10 2 value of ethyl octanoate decreasing from 12.81 without tartaric acid to 3.61 at 4 g/L, whereas aromatic ester release remained relatively stable. 1 H NMR showed more pronounced spectral responses for medium-chain and some aromatic esters. Quantum chemical calculations indicated that tartaric acid interacted noncovalently with fruity esters mainly through hydrogen bonding and hydrophobic interactions. Medium-chain esters exhibited stronger hydrogen-bonding interactions, whereas aromatic esters showed stronger hydrophobic contributions. Overall, 4 g/L tartaric acid was most favorable for short-chain and aromatic ester perception, whereas branched-chain ester perception was optimal at 2 g/L and medium-chain ester perception was generally inhibited by tartaric acid. Download: Download high-res image (233KB) Download: Download full-size image