Abstract:To explore the change patterns of the physical and chemical indicators as well as flavor substances of Huangshui during the fermentation process of Wuliang Nongxiang baijiu (NXB), Huangshui from the fermented grains of NXB was sampled continuously during the fermentation process to evaluate its physical and chemical properties. The flavor substances in Huangshui were analyzed by combining headspace solid-phase microextraction with gas chromatography-mass spectrometry (HS-SPME/GC-MS) and high-performance liquid chromatography (HPLC); thereafter, the physical and chemical indicators and flavor substances of Huangshui on different days were compared. The pH of Huangshui was stable at 3.35~3.50 throughout the fermentation period, and acidity peaked to reach 57.77 mmol/100 mL on the 35th day. The contents of starch and reducing sugars showed a decreasing trend, while alcohol content reaches a peak of 3.41% (volume) on the 28th day. The content of solids fluctuated greatly, which was related to changes in the contents of starch and reducing sugars. The results of orthogonal partial least squares discriminant analysis (OPLS-DA) showed large differences in flavor substances of Huangshui on different fermentation days, and the variable importance in projection (VIP) of 11 flavor substances, primarily esters and acids, exceeded 1. Ethyl lactate and ethyl hexanoate were produced in large quantities between the 7th and 35th days, whereas ethyl acetate and ethyl butyrate were accumulated in large quantities between the 42nd and 70th days. This study explored the change patterns of Huangshui during the fermentation process of NXB, which has a certain reference value for monitoring the NXB fermentation process with Huangshui as the medium.
