Comparison of two methods for detection of Listeria monocytogenes in foods
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摘要: 研究比较不同杂菌污染条件下平板计数(Plate counting)法和稀释培养计数(Most probable number counting)法检测食品中单核细胞增生李斯特氏菌(Listeria monocytogenes,LM)含量的准确性,并探讨冷藏和冷冻食品,MPN保存过程中LM的数量增长情况。采用国标法中的平板计数法和MPN计数法对不同程度人工污染杂菌的牛奶、凉拌菜和盐水鸭分别进行LM含量的检测,并用MPN计数法对冷藏(2~8℃)和冷冻(-20℃)条件下保存的牛奶、凉拌菜和盐水鸭进行LM含量的检测。结果表明,杂菌染菌浓度较低时(LM含量与杂菌含量比为10:1), LM检出限较高(≥ 100 CFU/g (mL)),平板计数法检测LM含量的准确性较高,而杂菌染菌的初始浓度较高时(LM含量与杂菌含量比为1:10),LM检出限较低(< 100 CFU/g (mL)),MPN计数法检测LM含量的准确性较高;牛奶、凉拌菜和盐水鸭在经过不同冷藏和冷冻保存时间后LM数量对比差异有统计学意义(p<0.05),且食品中LM数量随着冷藏和冷冻保存时间的增加而增多。
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关键词:
- 食品 /
- 平板计数法 /
- MPN计数法 /
- 单核细胞增生李斯特氏菌
Abstract: Plate counting and MPN counting methods were used to detect Listeria monocytogenes in foods under different conditions of contamination for screening an accurate one, and the quantity of LM in the refrigenerated and frozen foods at different storage times was explored. The LM content of milk, salad and saltwater ducks with different degrees of artificial contamination were detected by Plate counting and MPN counting methods respectively. The LM content of milk, salad and saltwater ducks stored in cold storage(2~8℃) and frozen(-20℃) were tested by MPN counting method.The results showed that the accuracy of Plate counting method was higher than MPN counting method when the concentration of bacteria was low (LM:E.coli and SA is 10:1) and the detection limit of LM was high (≥ 100 CFU/g (mL)) while it was lower than MPN counting method in the condition of the high initial concentration of bacteria(LM:E.coli and SA is 1:10) and the detection limit of LM(< 100 CFU/g(mL)).The number of LM in foods(milk,salad and saltwater ducks) increased with the increase of cold storage and frozen time, and the number of LM in the above storage time of milk, salad and saltwater ducks had statistic significance(p<0.05).-
Keywords:
- foods /
- plate counting method /
- MPN counting method /
- Listeria monocytogenes
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