食品链的微生物学 极限值的测定与应用

[中文适用范围]： 本文件确立了基本原则，并规定了确定细菌和酵母菌株的基本值并用其预测微生物生长的要求和方法。 该方法的四个主要步骤是： a) 在培养基中确定基本值； b) 在目标食品中确定校正因子； c) 模型验证； d) 模拟。 考虑了四个环境因素：温度、pH、水活度和抑制剂（例如有机酸）。 注1：微生物竞争在本文件中不被视为抑制剂，可以通过适当的建模方法解决。 基本值的确定采用两步法： — 在研究的菌株于特定环境因素值范围内在肉汤中生长时，确定其最大比生长速率； — 使用公认的预测微生物学二级模型来拟合获得的实验数据，以获得基本值。 在微生物生长模拟中使用基本值是基于预测微生物学的一级和二级模型。基本值与挑战测试数据相结合以考虑基质效应。 根据生长模拟的目标，考虑细菌或酵母物种内菌株间基本值的变化非常重要。 基本值是菌株对所研究环境因素生长能力的一个良好指标。因此，在进行生长挑战测试（见ISO 20976-1）或方法验证（见ISO 16140系列）时，除了菌株的来源和毒力外，它们也被用作选择菌株的标准。 注2：本文件侧重于确定一个菌株的基本值。同样的方法可以独立地用于表征多个菌株，以覆盖生物菌株的变异性，并将这些结果纳入预测中。 [外文原描述]： This document establishes basic principles and specifies requirements and methods to determine the cardinal values of bacteria and yeast strains and use them to predict microbial growth. The four main steps of the approach are: determination of the cardinal values in culture medium; determination of the correction factor in the target food; validation of the model; simulations. Four environmental factors are considered: temperature, pH, aw and inhibitors (e.g. organic acids). NOTE 1 Microbial competition is not considered as an inhibitor in this document and can be addressed by proper modelling approaches. The determination of cardinal values is performed in a two-step approach: the determination of maximum specific growth rates of the studied strain grown in broth under a defined range of values of the studied environmental factor(s); the use of recognized predictive microbiology secondary models to fit the obtained experimental data to obtain the cardinal values. The use of cardinal values in microbial growth simulation is based on predictive microbiology primary and secondary models. The cardinal values are combined with challenge test data to consider the matrix effect. Depending on the goal of the growth simulation, it is important to account for variation of cardinal values between strains within a bacterial or yeast species. Cardinal values are a good indicator of a strain growth ability for the studied environmental factors. They are therefore used as criteria to select strains, in addition to their origin and virulence, when performing growth challenge tests (see ISO 20976-1) or in methods validation (see ISO 16140 series). NOTE 2 This document focuses on the determination of cardinal values for one strain. The same methodology can be used to characterize multiple strains independently to cover biological strain variability and include these results in the predictions.