Changes in Volatile Compounds of Chinese Rice Wine Wheat Qu During Fermentation and Storage

In order to understand the optimum time of using wheat Qu for Chinese rice wine brewing on the basis of the contents of volatile compounds, changes in volatile compounds of Chinese rice wine wheat Qu during fermentation and storage were studied by headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrum (GC-MS). It was shown that the concentrations of most groups of volatiles, including alcohols, aldehydes, aromatic compounds, phenols, sulphides, furans, and nitrogen-containing compounds, increased progressively from the first day to the fourth day of fermentation, and then decreased gradually. A minority group of volatile compounds such as acids and ketones peaked after one day of fermentation, esters increased slowly from the first day to the eighth day of fermentation. Lactones and esters rose slowly from the first day to the fifteenth day of fermentation respectively, and decreased afterwards, whereas the evolution of terpenes was somewhat erratic. These results suggested that changes in the concentrations of most groups of volatile compounds during fermentation and storage were uniform. This made it possible to determine the optimum level of fermentation and storage for Chinese rice wine wheat Qu on the basis of the contents of volatile compounds.