Dynamics of Flavor Components during Fermentation of Yibin Yacai

The dynamics of flavor components including organic acid and amino acid contents as well as physical and chemical parameters during the fermentation process of Yibin Yacai,a special kind of pickled mustard stems with soy sauce,were investigated in this study.Results showed that throughout the fermentation process,the contents of salt,moisture and amino nitrogen were kept constantly at about 44%,8.5% and 0.1515%,respectively.Reducing sugar and pH decreased to 0.163% and 5.30 in finished products.The contents of oxalic acid and tartaric acid also decreased gradually,by about 22% and 65%,respectively in 20-d fermented samples when compared with finished products.However,the contents of malic acid,lactic acid and acetic acid increased gradually,by 40%,61% and 129%,respectively at the end of fermentation in comparison with those observed at 20 days of fermentation.In addition,there were only minor changes in the contents of succinic acid and total acid.Except tyrosine the contents of all amino acids became higher.The contents of Glu and Asp as the major amino acids responsible for umami reached 0.966% and 1.929%,respectively at the end of fermentation,which were increased by 235% and 198%,respectively compared with the levels at 20 days of fermentation.