Hassani M, Mañas P, Raso J, Condón S, Pagán R
Departamento Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain.
J Food Prot. 2005 Apr;68(4):736-43. doi: 10.4315/0362-028x-68.4.736.
The aim of this study was to find a model that accurately predicts the heat inactivation of Listeria monocytogenes (ATCC 15313) at constantly rising heating rates (0.5 to 9 degrees C/min) in media of different pH values (4.0 to 7.4). Survival curves of L. monocytogenes obtained under isothermal treatments at any temperature were nearly linear. Estimations of survival curves under nonisothermal treatments obtained from heat resistance parameters of isothermal treatments adequately fit experimental values obtained at pH 4.0. On the contrary, survivors were much higher than estimations at pH 5.5 and 7.4. The slower the heating rate and the longer the treatment time, the greater the differences between the experimental and estimated values. An equation based on the Weibullian-like distribution, log S(t) = (t/delta)p, accurately described survival curves of L. monocytogenes obtained under nonisothermal conditions within the range of heating rates investigated. A nonlinear relationship was observed between the scale parameter (delta) and the heating rate, which allowed the development of an equation capable of predicting the inactivation rate of L. monocytogenes under nonisothermal treatments at pH 5.5 and 7.4. The model predictions were a good fit to the measured data independent of the magnitude of the thermotolerance increase. This work might contribute to the increase in safety of those food products that require long heating lag phases during the pasteurization process.
本研究的目的是找到一个模型，该模型能准确预测在不同pH值（4.0至7.4）的培养基中，以持续上升的加热速率（0.5至9摄氏度/分钟）对单核细胞增生李斯特菌（ATCC 15313）进行热灭活的情况。在任何温度下进行等温处理所获得的单核细胞增生李斯特菌的存活曲线几乎呈线性。从等温处理的耐热参数得出的非等温处理下存活曲线的估计值与在pH 4.0时获得的实验值充分拟合。相反，在pH 5.5和7.4时，存活者数量远高于估计值。加热速率越慢且处理时间越长，实验值与估计值之间的差异就越大。基于类威布尔分布的方程log S(t) = (t/δ)p，准确描述了在所研究的加热速率范围内非等温条件下获得的单核细胞增生李斯特菌的存活曲线。观察到尺度参数（δ）与加热速率之间存在非线性关系，这使得能够开发一个方程来预测在pH 5.5和7.4的非等温处理下单核细胞增生李斯特菌的失活速率。该模型预测与测量数据拟合良好，与耐热性增加的幅度无关。这项工作可能有助于提高那些在巴氏杀菌过程中需要长时间加热延迟阶段的食品的安全性。
