Changes of physiochemical indexes and flavor substances of Huangjiangshui during brewing process of strong-flavor Baijiu

In this study, the Huangjiangshui was sampled continuously during the fermentation process of strong-flavor(Nongxiangxing)Baijiu(within 28 weeks), and the main physicochemical indexes and flavor substances were investigated. The results showed that the acidity of Huangjiangshui increased rapidly and the pH decreased rapidly in the early stage of fermentation. During 2-28 weeks of fermentation, the acidity was 3.45-4.71 ml/g and pH was 3.47-3.91. The starch content decreased sharply at the beginning of fermentation, then slowly, and finally approached 0. The alcohol content increased in the early stage of fermentation, reached the highest (13.99%vol) in the 6th week of fermentation, decreased in the middle stage of fermentation, and increased and stabilized at 9.08%vol-9.36%vol in the late stage. The total content of main flavor substances increased in the early stage of fermentation, decreased in the middle and late stage, and increased and stabilized in the late stage in the range of 50240.69-60561.74 mg/L. Acid content increased to 54160.75 mg/L at the 9th week of fermentation, then decreased, and finally fluctuated in the range of 43811.51-57237.04 mg/L. The alcohol and ester substances contents increased in the early stage of fermentation, reached the highest and fluctuated in the 9-11 weeks of fermentation, and then tended to be stable, with alcohol contents stabled in the range of 707.50-790.26 mg/L and ester contents stabled in the range of 1990.90- 2266.28 mg/L. The phenolic substances content remained basically unchanged in the early stage, increased in the middle stage, and stabilized and reached the highest(12652 μg/L)in the late stage.