Analysis of changes in simulated rancidification process during the storage of Huangjiu

Huangjiu, a traditional Chinese wine with low alcoholic strength, can easily develop rancidification upon microbial contamination in the long-term storage process. In order to analyze the changes in key indexes in the rancidification process during the storage of Huangjiu, a laboratory simulation of microbial contamination changes was carried out. Changes in microbiological indexes, physicochemical indexes, and volatile flavor compounds in the rancidification process of Huangjiu can be divided into two stages. Test results demonstrated that within the early stage of the rancidification process, multiplication of contaminating microorganisms was in the adaptation phase with a slow OD₆₀₀ growth value of Huangjiu, while physicochemical indexes such as the pH and amino acid nitrogen content changed relatively slowly. The contents of aldehyde compounds in the volatile flavor components of Huangjiu declined quickly to be lower than 1.0 mg/L, while the conductivity index increased by 6%. In the late stage, the OD₆₀₀ value of Huangjiu increased rapidly and microorganism multiplication entered the logarithmic phase. Furthermore, changes in the physicochemical indexes are accelerated. Specifically, the histamine content increased by 457% and the content of aldehydes remains lower than 1.0 mg/L. The conductivity index continued to rise by 25% in this stage. This indicates that the two rancidification stages have different influences on the quality of Huangjiu. The conductivity value can be used as a staged representative index throughout the rancidification of Huangjiu to distinguish between different batches and evaluate the degree of microbial contamination. Additionally, the conductivity index can be used for long-term online monitoring of large tank storage of Huangjiu.