Abstract:

Dynamic changes in the numbers of six microbial populations at different stages of natural fermentation of
Chinese leaf mustard (Brassica juncea coss) were investigated by microbial culture methods. The results showed that the
fermentation process of Chinese leaf mustard included three stages: 1) the fermented juice was at a pH greater than 5.0,
the numbers of total bacteria, Enterobacteriaceae and yeast were increased and subsequently decreased, and the dominant
bacterium was Lactobacillus, reaching 106 CFU/g; 2) the pH of fermented juice was reduced to below 5.0, the numbers of
total bacteria, Enterobacteriaceae and yeast were fluctuated within orders of magnitude of 105, 104 and 105, respectively,
and Lactococcus became the dominant bacterium at an order of magnitude of 106, compared to 105 for Lactobacillus;
3) the pH of fermented juice was further reduced to smaller than 4.0, the numbers of total bacteria and yeast began to
significantly decline, the growth of Enterobacteriaceae was almost inhibited, and Lactococcus remained dominant at a
level of 104, whereas acetic acid bacteria were always at very low levels. Artificial fermentation with a composite starter
culture consisting of Lactobacillus and Lactococcus at appropriately low levels of initial pH may be an alternative to natural
fermentation.

Key words: Chinese leaf mustard, fermentation, microfloral change