Enrichment of oligopeptides in sauce-aroma Baijiu by optimized distillation with soy sauce byproduct and their effect on Baijiu flavor

To enrich oligopeptides in sauce-aroma Baijiu, a mixed distillation process using the fermented grains from the eighth-round fermentation of sauce-aroma Baijiu brewing process and the residue from soy sauce pressing process was optimized. Under the optimum distillation conditions, the peptide concentration in mixed distillate was increased to 912.6 mg/L. Additionally, the structural characterizations of oligopeptides in distillates were identified by liquid chromatography-mass spectrometry (LC-MS). Thirty-nine oligopeptides were identified from the mixed distillate and presented characterizations of low mass, strong hydrophobicity, and potential biological activity, such as Leu-Pro-Phe, Pro-Leu-Phe, Leu-Leu-Tyr, Try-Val-Pro, and Leu-Tyr-Pro. Furthermore, their effects on Baijiu flavor were clarified by e-nose sensor, e-tongue sensor, and molecular docking. Mixed distillate possessed obvious umami, sweetness, and preferable flavor affinity, which may be attributed to the formation of hydrogen bonds between oligopeptides and flavor substances in Baijiu. It confirmed the feasibility of enriching oligopeptides by mixed distillation with the fermented grains of sauce-aroma Baijiu and soy sauce residue and benefited to improve the flavor of sauce-aroma Baijiu from the eighth-round fermentation.