以新鲜生菜作为研究对象,分析表面细菌种类,自制鲜切生菜置于4℃下贮藏10 d,结合感官评审、微生物计数和形态学观察,初步判断可能的优势腐败细菌,分离纯化并做回接实验,进一步比较准确地判断是否为优势腐败细菌,通过部分典型生理生化实验和分子生物学鉴定,确定优势腐败细菌。结果表明:生菜原料中M1-1、P1为微小杆菌(Exiguobacterium),V4、M1-4为肠杆菌(Enterobacter),M3为芽孢杆菌(Bacillus);贮藏在4℃下的鲜切生菜优势腐败细菌为M1-1微小杆菌(Exiguobacterium),M1-2、P2不动杆菌(Acinetobacter),M1-3单胞菌(Stenotrophomonas),N1、V3泛菌(Pantoea),V2肠杆菌(Enterobacter);其中,Exiguobacterium sp.M1-1为鲜切生菜贮藏过程中特有的优势腐败细菌。

The objective of this study was to analyze the dominant spoilage bacteria of fresh-cut lettuce stored at4 ℃ for 10 days. Based on the surface bacterial species of raw lettuce combined with sensory changes and microbial count and morphology,the possible dominant spoilage bacteria were found preliminarily. In the vitro experiments,10mL broth cultured about 18 h was dissolved in 990 mL physiological salinewith solid-liquid ratio 1∶ 10,in which the processed fresh-cut lettuce were suspended 15 s,and the samples was respectively stored at 4 ℃ for further determination of the dominant spoilage bacteria typically based on physiological and biochemical experiments and molecular identification. The results indicated that Exiguobacterium( M1-1 and P1),Enterobacteriaceae( V4 and M1-4),Bacillus( M3) isolated from the raw lettuce,and Exiguobacterium( M1-1),Acinetobacter( M1-2 and P2),Aeromonas( M1-3),Pantoea( N1 and V3),Enterobacteriaceae( V2) isolated from the fresh-cut lettuce stored at 4℃ were dominant spoilage bacteria. Furthermore,Exiguobacterium( M1-1) was the specific spoilage bacteria. Therefore,it was very important to analyze species and living conditions about the initial bacteria of raw lettuce and dominant spoilage bacteria of fresh-cut lettuce,to control the quality of fresh-cut lettuce and shelf life.