Abstract:

In this study, cooked soybean was fermented by mixed cultures of Aspergillus oryzae and Aspergillus niger,
pure Aspergillus oryzae and the traditional method, respectively. The volatile compound of three Douchi samples was
analyzed and compared by gas chromatography-mass spectrometry (GC-MS). A total of 152 volatile compounds, i.e.,
30 hydrocarbons, 21 alcohols, 8 aldehydes, 33 esters, 7 ketones, 6 phenols, 18 acids, 20 heterocyclic compounds, 3
sulfocompounds and 6 other compounds, were identified. Results showed that the contents of hydrocarbons, aldehydes
and acids in Douchi produced by mixed culture fermentation were higher than in that from pure culture fermentation. The
traditional fermented Douchi had higher contents of alcohols, heterocyclic compounds sulfocompounds and phenols when
compared with the two other samples. On the other hand, the multi-strains fermented Douchi contained significantly higher
amounts of ketones and esters when compared with the pure culture and the traditional fermented Douchi.

Key words: Douchi, fermentation, volatile compounds