延长初发酵培养时间对各类样本大肠菌群结果影响分析

Effect of prolonging time of first fermentation on results of coliform bacteria among different categories of samples

目的:旨在了解延长初发酵培养时间对各类样本大肠菌群检出结果的影响。方法:将国标大肠菌群多管发酵法(GB/T4789.28-2003)要求的初发酵培养时间18-24 h延长至36-48 h,对7个种类343份样本进行大肠菌群总数检测。结果:延长初发酵时间后有80份(23%)样本大肠菌群总数增加,各类样本中大肠菌群增加的样本率依次为沙拉46%、果汁饮料44%、蔬菜29%、含奶冰冻饮品22%、食用冰块17%、过滤水16%和环境涂抹样本6%。比较各类样本在18-24 h和36-48 h大肠菌群总数超标率差异,果汁在两个不同发酵时间的大肠菌群超标阳性率差异具有统计学意义(2χ=15.82,P<0.01)。结论:延长初发酵培养时间可不同程度提高大肠菌群成员检出率,为某些样本的国标大肠菌群多管发酵法修订提供了试验依据。

Objective：To know the effect resulted from prolonging of primary fermentation time on coliform bacteria among different categories of samples. Methods：The time of primary fermentation was prolonged from 18 -24 h which is stipulated by multitube fermentation detection of coliform bacteria （ GB/T4789. 3 - 2003 ） to 36- 48 h, and 343 samples of 7 categories were investigated. Results ：The concentration of total coliforms was increased in 80 samples, which accounted for 23%. The positive rate of 7 categories of samples was salad （44%）, fruit juice （46%）, vegetables （27%）, ice beverage of cream （22%）, edible ice （17%）, filtration water （16%）, and environmental samples （6%） ,respectively. Compared positive rate of transnormal standard of total coliforms during 18 - 24 h with one during 36 - 48 h, the difference in fruit juice had statistical significance （ P 〈 0. 01 ）. Conclusion：Prolonging the primary fermentation time may increase detectable rate of coliform bacterial members by different extent, and it could provides the modification basis for national standard method of multitube fermentation detection.