真空包装淡腌青鱼品质和细菌类型及数量

在零售市场和生产企业抽取4批真空包装淡腌青鱼,对其感官、化学和细菌学品质特性进行分析,并对细菌类型和数量进行研究。结果显示,产品栅栏因子及强度存在差异,盐分含量6.68%~12.06%,平均值(9.36±2.2)%;水分活度值0.75~0.91,平均值0.82±0.07;pH值6.00~6.30,平均值6.20±0.13。栅栏因子种类和强度的不同决定产品品质的差异,感官评价均可接受,过氧化值均值为19.65±8.75 meq/kg,挥发性盐基氮均值为24.50±15.30 mg/100 g,菌落总数均值为4.45±1.15 cfu/g,大肠菌群均低于30 MPN/100 g。从4批淡腌青鱼样品分离到234株细菌,73.9%是革兰氏阳性细菌,其中36.3%是葡萄球菌,31.6%是链球菌,并出现少量微球菌和棒状杆菌;由需氧革兰氏阴性杆菌不动杆菌、摩氏杆菌和鞘氨醇单胞菌组成较小的细菌菌群约占总细菌群落的18.4%,显示水分活度、盐分含量和pH值等栅栏因子与产品细菌类型和数量呈一定相关性。

Bacterial numbers and types as well as quality of vacuumized and lightly salted black carp(Mylopharyngodon piceus)

Four packages of vacuumized linghtly salted Black carp taken from two supermarkets and two factories have been carried out on the examination of sensorial,chemical and microbiological characteristics as well as type and numbers of survival bacteria.The results showed that the levels of hurdle factors such as temperature,pH,water activity(Aw) were variable,for example,salt content was from 6.68% to 12.06%,mean value was 9.36±2.2%;water activity of products ranged between 0.75 to 0.91,mean value was 0.82±0.07;pH varied from 6.00 to 6.30,average value was 6.20±0.13.Level and type of hurdle factors were variable and related to sensory scores,total volatile basic nitrogen or the numbers of bacteria.Levels of total volatile basic nitrogen,peroxide value, total bacteria counts and coliform group were 24.50±15.30 mg/100 g,19.65±8.75 meq/kg,4.45±1.15 cfu/g,and less than 30 MPN/100 g respectively.Among 234 bacteria isolates obtained from four batches of lightly salted samples,Gram negative bacteria occupied 73.9%,were composed of Streptococcus spp.(31.6%),Staphylococcus spp.(36.3%),a few percentage of Corynebacterium spp.and Micrococcus spp.were also found.Minor microbial groups such as aerobic Gram-negative bacilli(Psychrobacter spp.,Moraxella spp.and Shinganonas spp.) constituted 18.4% of the total flora.It revealed that pH,Aw,salt content of hurdle factors were in agreement with sensory analysis,numbers and types of survival microorganisms on lightly salted products.