Decoding the Qu-aroma of medium-temperature Daqu starter by volatilomics, aroma recombination, omission studies and sensory analysis

Qu -aroma is of great significance for evaluation the quality of Daqu starter. This study aimed to decode the Qu -aroma of medium-temperature Daqu (MT- Daqu ) via “top-down” and “bottom-up” approaches. Firstly, 52 aroma descriptors were defined to describe the MT- Daqu aroma by quantitative descriptive analysis . Secondly, 193 volatile organic compounds (VOCs) were identified from 42 MT- Daqu samples by HS-SPME-GC–MS, and 43 dominant VOCs were screened out by frequence of occurrence or abundance. By Thin Film (TF)-SPME-GC-O-MS, 27 odors and 90 VOCs were detected in MT- Daqu mixture, and 14 odor-active VOCs were screened out by odor intensity. Thirdly, a five-level MT- Daqu aroma wheel was constructed by matching 52 aroma descriptors and 37 aroma-active VOCs. Finally, Qu -aroma of MT- Daqu was reconstructed with 37 aroma-active VOCs and evaluated by omission experiments. Hereinto, 26 key aroma-active VOCs were determined by OAV value ≥1, including isovaleric acid, 1-hexanol, isovaleraldehyde, 2-octanone, trimethylpyrazine, γ-nonalactone, 4-vinylguaiacol, etc.