巴氏杀菌奶中单增李斯特菌生长动力学模型的研究

为研究巴氏杀菌奶中单增李斯特菌的生长规律,将4株单增李斯特菌混合接种到巴氏杀菌奶中,并分别置于4、8、12、16、20、25、30、37、40、43℃条件下恒温培养,间隔时间取样计数。使用美国农业部开发的IPMP 2013软件,将4~43℃条件下得的生长数据分别代入Huang模型和Baranyi模型进行拟合,分析单增李斯特菌在不同温度下的生长动力学特征。在所有温度下均可以观察到单增李斯特菌的生长,所有生长曲线都显示出滞后期,指数期和稳定期。综合比较2种初级模型的RMSE、RSE、AIC和生长速率,确定Baranyi模型和Huang模型均适合描述巴氏杀菌奶中单增李斯特菌的生长,且具有等同的拟合效果。采用Ratkowsky平方根模型、Huang平方根模型和Cardinal模型描述温度对巴氏杀菌奶中单增李斯特菌生长速率的影响。研究表明:3种模型都能用于评价温度对其生长速率的影响。Ratkowsky平方根模型预测的单增李斯特菌的最低、最高温度为0.218℃和46.389℃,与文献报道的更为接近。因此,Ratkowsky平方根模型比Huang平方根模型和Cardinal模型更适合描述温度对单增李斯特菌生长的影响。建立的模型可为相关监管部门开展巴氏杀菌奶中单增李斯特菌的安全风险评估提供科学依据。

Growth kinetics model of listeria monocytogenes in pasteurized milk

The growth kinetics of Listeria monocytogenes in pasteurized milk was investigated. Samples inoculated with four-cocktail-strains of Listeria monocytogenes were incubated at 4, 8, 12, 16, 20, 25, 30, 37, 40, 43 ℃, to develop kinetic growth models. The growth kinetics of Listeria monocytogenes at the test temperatures were analyzed by curve-fitting to the Huang models and Baranyi models using the USDA Integrated Pathogen Modelling Program(IPMP, 2013). The growth of Listeria monocytogenes in pasteurized milk could be observed at all temperatures,and all growth curves exhibited lag, exponential and stationary phases. Both of the Baranyi model and Huang model were suitable to describe the growth of Listeria monocytogenes in pasteurized milk. Secondary models, including the Ratkowsky square-root model, Huang square-root model, and Cardinal model were chosen for evaluating the effect of temperature on specific growth rates. The results shown that all three models were suitable for evaluating the effect of temperature on growth rate. Ratkowsky square-root model to predict the single increase of Listeria monocytogenes the minimum, the highest temperature were 0.218 ℃ and 46.389 ℃, and more closed to the reported in literatures.Therefore, the Ratkowsky square-root model was more suitable than the Huang square-root model and the Cardinal model to describe the effect of temperature on the growth of Listeria monocytogenes. The model could provide scientific basis for the safety risk assessment of Listeria monocytogenes in pasteurized milk.