Lactic acid modulates empty-cup aroma persistence in Baijiu via molecular interaction mechanisms: a case study of strong-aroma and soy-sauce-aroma Baijiu.

Empty-cup aroma persistence (ECAP) is a key indicator of Baijiu quality, yet mechanisms underlying its modulation remain unclear. GC-MS analysis revealed that ECAP positively correlation with medium-/long-chain esters/aldehydes/acids and lactic acid (LA), while certain volatiles showed negative correlation, which possibly due to flavor interactions involved low-volatility like LA. QDA and E-nose detection confirmed that LA supplementation (5-25 g/L) prolonged ECAP by 25% in strong-aroma and 300% in soy-sauce-aroma Baijiu. In 52% ethanol-water model, 1H NMR demonstrated LA (0.297-4.476 g/L) transformed ethanol hydrogen-bonding from chain-like (δ 5.350 ppm) to tetrahedral (δ 4.780 ppm) configurations. Downfield shifts (Δδ -0.091 to -0.111 for ethanol -OH; -0.46 to -0.50 for LA -CH) confirmed new hydrogen bonds. Partition coefficient (kg/m) and molecular dynamics simulations indicated that LA concentration-dependently suppressed ethanol (optimal: 0.595 g/L). These findings demonstrated that LA enhanced ECAP through hydrogen-bonding network restructuring, providing scientific basis for intelligent Baijiu blending.