Microbiological and biochemical changes during processing of the traditional chinese food douzhi

The microbiological and biochemical changes during douzhi processing were studied. The sedimentation process was shown to follow a lactic fermentation course. The main fermenting bacteria were identified to be Lactococcus lactis and Leuconostoc citreum; the former played the main role in producing acids, and the latter ensured a better flavor of douzhi. Yeasts thrived during the late part of fermentation were believe to account for the decrease in acidity. Tracing the change of chemical compounds suggested that active metabolic activity was induced when beans were steeped in water, in which significant reduction in crude protein and sugars were observed, but levels of soluble proteins, free amino acids increased. Fermentation by lactic acid bacteria caused a rapid reduction of soluble proteins, soluble sugars and reducing sugars, but significant accumulation of free amino acids and slight changes in crude protein. Mung bean endogenous protease and amylase activity dropped significantly during fermentation.