Department of Agricultural and Food Sciences, University of Bologna, Via del Florio 2, Ozzano dell'Emilia, BO, Italy.
Department of Physics and Astronomy, University of Bologna, viale Berti Pichat, 6/2, Bologna, Italy.
Food Microbiol. 2018 Dec;76:154-163. doi: 10.1016/j.fm.2018.04.013. Epub 2018 Apr 30.
The aim of this study was to model Listeria monocytogenes growth kinetics in ready to eat full meal pasta salads, containing fresh and cooked ingredients. With this aim, laboratory prepared salads, representing two formulations of commercial pasta salads, were spiked with L. monocytogenes and tested under categorised packaging and storage temperature conditions. L. monocytogenes enumeration results collected in 15 different laboratory prepared salad datasets were analysed with primary and secondary models. The models showing the best fit to describe L. monocytogenes growth kinetics in the laboratory prepared salads were then validated within commercial pasta salads. Baranyi no-lag was the best primary model fitting datasets collected at 12 °C, whereas the exponential model gave the best results for datasets collected at 4 °C. The maximum microbial specific growth rate (μ) mean values obtained at 4 and 12 °C for salads packaged under air packaging conditions were 0.008 ± 0.003 and 0.036 ± 0.006 log (cfu/g) h, respectively. At the same temperatures, the μ mean values obtained under modified atmosphere were 0.005 ± 0.005 and 0.026 ± 0.005 log (cfu/g) h, respectively. The Gamma secondary model predicted the growth kinetics of L. monocytogenes at both temperatures and packaging conditions and the μ at the optimum temperature and the optimum pH for Listeria growth (μ) estimated by the model corresponded to 0.247 ± 0.009 log (cfu/g) h. Baranyi model without lag phase was used to generate growth kinetics under different scenarios. In the comparison of the predicted log concentrations respect to the observed ones the residues rarely exceeded 1 Log cfu/g. The selected models can be applied to describe the growth kinetics of L. monocytogenes in similar types of pasta salads with comparable pH, shelf life and storage conditions.
本研究旨在建立即食全餐意大利面沙拉中李斯特菌生长动力学模型，该沙拉包含新鲜和熟制食材。为此，研究使用实验室制备的沙拉，模拟两种商业意大利面沙拉配方，向其中添加李斯特菌，并在分类包装和储存温度条件下进行测试。在 15 个不同的实验室制备沙拉数据集上收集李斯特菌计数结果，使用主要和次要模型进行分析。然后，在商业意大利面沙拉中对最佳拟合描述实验室制备沙拉中李斯特菌生长动力学的模型进行验证。在 12°C 下收集的数据集，Baranyi 无滞后模型拟合效果最好；而在 4°C 下收集的数据集，指数模型拟合效果最好。在空气包装条件下，4°C 和 12°C 下包装的沙拉的最大微生物比生长速率（μ）平均值分别为 0.008±0.003 和 0.036±0.006 log(cfu/g) h。在相同温度下，在改良气氛下获得的μ平均值分别为 0.005±0.005 和 0.026±0.005 log(cfu/g) h。Gamma 二级模型预测了两种温度和包装条件下李斯特菌的生长动力学，并且模型估计的最适温度和最适李斯特菌生长 pH 下的μ值为 0.247±0.009 log(cfu/g) h。不带有滞后期的 Baranyi 模型用于生成不同场景下的生长动力学。在预测对数浓度与观测对数浓度的比较中，残差很少超过 1 Log cfu/g。所选模型可用于描述具有类似 pH、保质期和储存条件的类似类型的意大利面沙拉中李斯特菌的生长动力学。
