灭菌乳中嗜热脂肪芽孢杆菌商业无菌的最低可视浓度的测定

目的 测定灭菌乳中嗜热脂肪芽孢杆菌的商业无菌检出限。方法 随机购买3种不同品牌的灭菌乳,分别添加10_⁵、10_⁴、10_³、10_²、10_¹、10_⁰ CFU/mL浓度的嗜热脂肪芽孢杆菌制成模拟样品,分别对培养4 d、7 d、9 d、10 d的样品按照GB 4789.26-2013《食品安全国家标准 食品微生物学检验 商业无菌检验》的检验方法检测。结果 3种品牌牛乳的模拟样品商业无菌的最低检出浓度均为10_¹ CFU/mL,同时发现培养10 d后样品中的嗜热脂肪芽孢杆菌并无明显的增殖也无菌落进入休眠状态。对培养10 d后的模拟样品进行菌落计数验证以上结论。结论 灭菌乳中嗜热脂肪芽孢杆菌商业无菌检出限为10_¹ CFU/mL,如果灭菌乳中存在嗜热脂肪芽孢杆菌浓度＜10_¹ CFU/mL时,可能在检验过程中对灭菌乳的芽孢菌出现漏检。灭菌乳中嗜热脂肪芽孢杆菌在培养后无明显增殖,符合商业无菌相对无菌标准。

Determination of the lowest visible concentration of commercial sterility of Geobacillus stearothermophilus in sterilized milk

Objective To determine the lowest visible concentration of commercial sterility of Geobacillus stearothermophilus in sterilized milk. Methods Three different brands of sterilized milk were randomly purchased, after adding 105, 104, 103, 102, 101, 100 CFU/mL concentration Geobacillus stearothermophilus to make a simulated sample, the samples cultured for 4, 7, 9, and 10 d were tested according to the inspection method of GB 4789.26-2013 National food safety standard-Food microbiological inspection-Commercial sterility inspection. Results After 7 d and 10 d of cultivation, the 3 brand simulation samples from number (X-1) to (X-5) (X represents the sample information number in Table 1) could all be observed in the field of view of Geobacillus stearothermophilus, at the same time, it was found that the Geobacillus stearothermophilus in the sample after 10 days of culture did not multiply a hundred times or more, and did not produce spores. Colony counts were performed on the simulated samples after 10 days of culture to verify the above conclusions. Conclusion The lowest commercial sterile concentration of Geobacillus stearothermophilus in sterilized milk is 101 CFU/mL. Geobacillus stearothermophilus in the sterilized milk do not proliferate significantly after 10 days of culture, and no colony enteres a dormant state. It showes that the contaminated Geobacillus stearothermophilus in the sterilized milk meets the commercial sterility relative sterility standard.