Characterization of volatile compounds from Daqu-a traditional Chinese liquor fermentation starter

Daqu is a fermentation starter and substrate complex that is used to initiate the solid fermentations for the production of Chinese liquor. The aroma of Daqu is one of the most important factors that influence the flavour of Chinese liquor. To further study the aroma of Daqu, volatile compounds in ten Daqu samples were extracted by headspace solid-phase microextraction (HS-SPME) and analysed by gas chromatography-mass spectrum (GC-MS). The samples were pre-equilibrated at 50 degrees C for 10 min and extracted with stirring at the same temperature for 30 min prior to injection into a GC-MS. A total of 75 volatile compounds were characterised by GC-MS, including twelve alcohols, eleven esters, eight acids, nine aromatic compounds, four phenols, two furans, fourteen nitrogen-containing compounds and fifteen aldehydes and ketones. By a principal component analysis (PCA), the ten Daqu samples could be classified into three groups according to their origins and, in particular, the production technologies.