Deciphering Qu-aroma in Nongxiangxing baijiu via a customized aroma base solution

Conventional evaluation of volatile organic compounds (VOCs) in distilled spirits relies on aqueous ethanol solutions, neglecting matrix effects that critically modulate odor perception. To address this, we developed a Nongxiang-aroma base solution containing 12 compounds to simulate the aroma skeleton of Nongxiangxing baijiu (NXXB), China's most consumed baijiu. Using this physiologically relevant medium, we systematically characterized Qu-aroma in NXXB, the distinctive olfactory signature derived from medium-temperature Daqu (MT-Daqu). Integrative analysis of 37 Qu-aroma VOCs detected in MT-Daqu with volatile profiles in 53 NXXB samples (analyzed via HS-SPME-GC-MS and SBSE-GC-MS/O) identified 17 Qu-aroma active VOCs. Odor thresholds measured in the base solution were up to >200-fold higher than those in ethanol solution, highlighting profound matrix-dependent suppression of aroma potency. By integrating odor activity values (OAVs) with sensory recombination and omission tests, we identified eight key Qu-aroma contributors in NXXB: five direct odorants (isovaleraldehyde, hexanal, 2-methylbutanal, isovaleric acid, 1-hexanol; OAVs > 1) and three modulatory odorants (1-pentanol, benzaldehyde, phenylacetaldehyde; 0.1 < OAV < 1). This study provides a matrix-mimetic, sensory-validated strategy for accurate VOC contribution assessment in complex spirits, advancing baijiu aroma science and quality-oriented innovation.