面筋食品中微生物群落分析及优势菌分离鉴定

为探明面筋食品腐败变质的主要污染途径和微生物群落,从生产线、大型超市和零售小卖部多地取样,用平板计数法检测菌落总数、霉菌酵母数、耐热菌和大肠菌群数,用划线法和点接法将优势菌分离,通过形态观察和理化试验,结合16S rDNA序列和18S rDNA的ITS区域序列进行优势菌鉴定。结果显示:小卖部样品的细菌总数达8×10~4 CFU/g,酵母霉菌数达1.20×10~3 CFU/g,都大大超过地方标准上限的数倍,其他样品的微生物数量均在地方标准之内,说明挤压熟化工艺有较好的杀菌效果,后期生产销售是造成污染的主要途径;分离优势菌得2类细菌12株,3类霉菌8株;2类细菌的代表菌为粪嗜冷杆菌(Psychrobacter faecalis)、黄褐假单胞菌(Pseudomonas fulva),3类霉菌的代表菌为溜曲霉(Asperqillus tamarii)、灰黄青霉(penicilium griseofulvum)和黑曲霉(Asperqillus niger)。

Analysis of microbial community and isolation and identification of their dominant microorganism in gluten food

To understand the dominant decaying microorganism, microflora composition and pollution pathways that causing gluten food deterioration, multiple samples of gluten foods were collected from various approaches, such as the factory production lines, large supermarket and small store. The total aerobic bacterial count, number of moulds and yeasts, coliforms and heat–resistance bacteria were tested using plate count method; the dominant microorganism were jointly isolated using plate streak method and point planting method, and their identification were based on the microscopic examination, physiological & biochemical test and the 16S rDNA gene sequence (the ITS sequence of 18S rDNA). The results showed that the total aerobic plate count from small store was 8×104 CFU/g, the number of moulds and yeasts reached to 1.20×103 CFU/g, which exceeded several times more than the limitation of local standard, while, the microbial populations from other sources of samples were in the scope of local standard. These results indicated that the extrusion technology was good for sterilization, but the later production and sale process was the main pathway leading to gluten food pollution. There 12 strains of bacteria which were subdivided into two categories and 8 strains of moulds which were subdivided into three categories were isolated in the test. The 2 dominant strains of bacteria were Psychrobacter faecalis,Pseudomonas fulva, and the 3 dominant strains of moulds wereAsperqillus tamarii,Penicilium griseofulvum andAsperqillus niger.