发酵乳中乳酸菌计数不确定度的评定

Uncertainty Evaluation of Lactic Acid Bacteria Count in Fermented Milk

目的:对发酵乳中乳酸菌计数不确定度的来源进行分析。方法:依据GB4789.35-2016《食品安全国家标准食品微生物学检验乳酸菌检验》进行测定,根据JJF1056.1-2012《测量不确定度评定与表示》与SN/T4091-2015《食品微生物学测量不确定度评估指南》对不确定度来源进行分析和评定。结果:乳酸菌计数过程中发散是引起不确定度的主因,同一样品重复测定结果的扩展不确定度为0.051 5(p=95%,k=2.26),一组样品重复测定结果的扩展不确定度为0.070 9(p=95%,k=2.23)。结论:合理选择评定方法,采用合并样本标准差的方法来评定乳酸菌检验的不确定度。

Objective： The source of measurement uncertainty of lactic acid bacteria count in fer-mented milk was analyzed. Methods： Lactic acid bacteria count was conducted under the direction of GB4789.35-2016 National food safety standard food microbiological examination： Lactic acid bacteria. Then, the uncertainty source introduced in the experiment were determined according to JJF1056.1-2012 Evaluation and expression of uncertainty in measurements and SN/T4091-2015 Guidelines for the measurement uncertainty for quantitative detections-Microbiological testing of food. Results： The divergence was the major cause of the uncertainty in the detection of counting total lactic acid bacteria. The extended uncertainty of the same sample repeatable results was 0.051 5（p=95%, k=2.26） and a set of same sample repeatable results was 0.070 9（p=95%, k=2.23）. Conclusion： The uncertainty of lactic acid bacteria measurement was evaluated with suitable evaluation methods; for instance the same standard deviation.