Abstract:The dynamic changes in the composition and content of volatile components during the solid-state fermentation to produce traditional Chinese vinegar Daqu were analyzed by headspace-solid phase microextraction–gas chromatography–tandem mass spectrometry (HS-SPME-GC-MS). A total of 56 volatile compounds, including 22 esters, 11 alcohols, 9 aldehydes, 3 ketones, 1 acid, 3 alkanes, 1 heterocyclic compound, 1 pyrazine, 3 benzene containing compounds, 1 amine and 1 other compound, were isolated and their quantities determined at various stages of fermentation. The quantities of most of these volatile components declined after the initial increase. Esters and alcohols reached their maximum values on days 3 and 7, respectively, and stabilized during the late stage of the fermentation; aldehydes and ketones reached their peak values on day 13, and gradually decreased afterwards. However, acids continued to increase until they attained the maximum value on day 30. Principal component analysis (PCA) was also performed to compare the profiles of the volatile components at various stages of the solid-state fermentation with those obtained by HS-SPME-GC-MS. The results from both methods were consistent. Both sets of results indicated that significant changes in the relative content of the volatile components occurred on days 3, 7, and 13 of the fermentation to produce Daqu, and the content tended to stabilize during the later stages of fermentation.
