湖南芥菜腌制发酵过程中的菌相变化规律

Changing Patterns of Microflora during Natural Fermentation of Chinese Leaf Mustard(Brassica juncea coss) Grown in Hunan Province, China

从动态角度研究湖南芥菜发酵过程中6种菌相阶段性变化,为其实现从自然发酵到人工发酵提供科学依据。结果表明:芥菜发酵主要分为3个阶段。第1阶段发酵液pH>5.0,细菌总数、肠道杆菌及酵母菌数量先下降后上升,乳酸球菌为优势菌种,数量达到106 CFU/g;第2阶段发酵液pH值降至5.0以下,细菌总数、肠道杆菌及酵母菌数量在一个数量级内上下波动,分别为105、104、105,乳酸杆菌成为优势菌种,数量级为106,球菌为105;第3阶段发酵液pH<4.0,细菌、酵母菌和乳酸菌的数量开始明显减少,肠道杆菌生长基本受到抑制,乳酸杆菌仍是优势菌种,数量级在104。醋酸菌数量一直处于一个非常低的水平。为实现芥菜的自然发酵到人工发酵,可以用乳酸球菌和乳酸杆菌组合当发酵剂,并且适当降低发酵初始pH值。

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.