Department of Food Science and Technology, Faculty of Veterinary, Agrifood Campus of International Excellence (CeiA3), University of Cordoba, Córdoba, Spain.
IRTA, Food Safety Programme, - Finca Camps i Armet s/n, 17121 Monells, Spain.
Int J Food Microbiol. 2019 May 16;297:72-84. doi: 10.1016/j.ijfoodmicro.2019.03.002. Epub 2019 Mar 6.
The objective of this work was to quantitatively evaluate the effect of Lactobacillus sakei CTC494 (sakacin-producing bioprotective strain) against Listeria monocytogenes in fish juice and to apply and validate three microbial interaction models (Jameson, modified Jameson and Lotka Volterra models) through challenge tests with gilthead sea bream (Sparus aurata) fillets under modified atmosphere packaging stored at isothermal and non-isothermal conditions. L. sakei CTC494 inhibited L. monocytogenes growth when simultaneously present in the matrix (fish juice and fish fillets) at different inoculation ratios pathogen:bioprotector (i.e. 1:1, 1:2 and 1:3). The higher the inoculation ratio, the stronger the inhibition of L. monocytogenes growth, with the ratio 1:3 yielding no growth of the pathogen. The maximum population density (N) was the most affected parameter for L. monocytogenes at all inoculation ratios. According to the microbiological and sensory analysis outcomes, an initial inoculation level of 4 log cfu/g for L. sakei CTC494 would be a suitable bioprotective strategy without compromising the sensory quality of the fish product. The performance of the tested interaction models was evaluated using the Acceptable Simulation Zone approach. The Lotka Volterra model showed slightly better fit than the Jameson-based models with 75-92% out of the observed counts falling into the Acceptable Simulation Zone, indicating a satisfactory model performance. The evaluated interaction models could be used as predictive modelling tool to simulate the simultaneous behaviour of bacteriocin-producing Lactobacillus strains and L. monocytogenes; thus, supporting the design and optimization of bioprotective culture-based strategies against L. monocytogenes in minimally processed fish products.
本工作的目的是定量评估乳杆菌 CTC494（产 sakacin 的生物保护菌株）对鱼汁中单核细胞增生李斯特菌的影响，并通过挑战测试，应用和验证三种微生物相互作用模型（Jameson、改良 Jameson 和 Lotka-Volterra 模型），用经过改良的气氛包装的金头鲷（Sparus aurata）鱼片在等温条件和非等温条件下储存。当乳杆菌 CTC494 同时以不同的接种比例（病原菌：生物保护剂）存在于基质（鱼汁和鱼片）中时，抑制了单核细胞增生李斯特菌的生长。接种比例越高，对单核细胞增生李斯特菌生长的抑制作用越强，比例为 1:3 时病原菌无生长。最大种群密度（N）是所有接种比例下对单核细胞增生李斯特菌影响最大的参数。根据微生物学和感官分析结果，对于 L. sakei CTC494 的初始接种水平为 4 log cfu/g 将是一种合适的生物保护策略，而不会损害鱼类产品的感官质量。通过可接受模拟区方法评估了测试的相互作用模型的性能。与基于 Jameson 的模型相比，Lotka-Volterra 模型的拟合效果略好，观察到的计数中有 75-92%落入可接受模拟区，表明模型性能良好。评估的相互作用模型可作为预测模型工具，模拟产细菌素的乳杆菌菌株和单核细胞增生李斯特菌的同时行为；从而支持针对加工最少的鱼类产品中的单核细胞增生李斯特菌的基于生物保护培养的策略的设计和优化。
