Extracellular proteolytic enzyme-mediated amino exposure and β-oxidation drive the raspberry aroma and creamy flavor formation

The fermentation-driving ability of Daqu has been widely reported, while the potential influence of substances in Daqu on Baijiu flavor formation has attracted increasing interest. Pseudo-targeted metabolomics integrated proteomics combined with sensory evaluation strategy was applied to investigate the correlation between flavor characteristics and metabolic profiling of Daqu, and the mechanism of flavor formation was also elucidated. The 4-hydroxy-2,5-dimethylfuran-3-one (3.5 mg kg−1) and 2,3-dihydro-1 h-inden-5-ol (894.3 μg kg−1) were identified as the unique substances in qingcha qu, which were vital for raspberry flavor formation and associated with the up-regulation of amino acid metabolism. The dec-9-enoic acid (37.4 mg kg−1) was screened out as the substance related to the formation of cream flavor in hongxin qu produced through the shortening of fatty acid carbon chains and unsaturated modification of long chain fatty and acceleration of carbon metabolism in hongxin qu mediated by filamentous Aspergillus spp. was related to the smoky aroma enhancement.