BioTeC+ - Chemical and Biochemical Process Technology and Control, KU Leuven, Gebroeders de Smetstraat 1, 9000 Gent, Belgium; OPTEC, Optimization in Engineering Center-of-Excellence, KU Leuven, Belgium; CPMF(2), Flemish Cluster Predictive Microbiology in Foods - www.cpmf2.be, Belgium.
Department of Food Science and Technology, International Campus of Excellence in the AgriFood Sector, University of Córdoba, C-1, 14014 Córdoba, Spain.
Int J Food Microbiol. 2018 Oct 20;283:7-13. doi: 10.1016/j.ijfoodmicro.2018.05.032. Epub 2018 Jun 1.
Traditionally, predictive growth models for food pathogens are developed based on experiments in broth media, resulting in models which do not incorporate the influence of food microstructure. The use of model systems with various microstructures is a promising concept to get more insight into the influence of food microstructure on microbial dynamics. By means of minimal variation of compositional and physicochemical factors, these model systems can be used to study the isolated effect of certain microstructural aspects on microbial growth, survival and inactivation. In this study, the isolated effect on microbial growth dynamics of Listeria monocytogenes of two food microstructural aspects and one aspect influenced by food microstructure were investigated, i.e., the nature of the food matrix, the presence of fat droplets, and microorganism growth morphology, respectively. To this extent, fish-based model systems with various microstructures were used, i.e., a liquid, a second more viscous liquid system containing xanthan gum, an emulsion, an aqueous gel, and a gelled emulsion. Growth experiments were conducted at 4 and 10 °C, both using homogeneous and surface inoculation (only for the gelled systems). Results regarding the influence of the growth morphology indicated that the lag phase of planktonic cells in the liquid system was similar to the lag phase of submerged colonies in the xanthan system. The lag phase of submerged colonies in each gelled system was considerably longer than the lag phase of surface colonies on these respective systems. The maximum specific growth rate of planktonic cells in the liquid system was significantly lower than for submerged colonies in the xanthan system at 10 °C, while no significant differences were observed at 4 °C. The maximum cell density was higher for submerged colonies than for surface colonies. The nature of the food matrix only exerted an influence on the maximum specific growth rate, which was significantly higher in the viscous systems than in the gelled systems. The presence of a small amount of fat droplets improved the growth of L. monocytogenes at 4 °C, resulting in a shorter lag phase and a higher maximum specific growth rate. The obtained results could be useful in the determination of a set of suitable microstructural parameters for future predictive models that incorporate the influence of food microstructure on microbial dynamics.
传统上，用于预测食品病原体生长的模型是基于在肉汤培养基中进行的实验建立的，因此这些模型不能包含食品微观结构的影响。使用具有不同微观结构的模型系统是深入了解食品微观结构对微生物动力学影响的一种有前途的方法。通过最小化组成和物理化学因素的变化，可以使用这些模型系统来研究某些微观结构方面对微生物生长、存活和失活的孤立影响。在这项研究中，研究了两种食品微观结构方面和一种受食品微观结构影响的方面对单核细胞增生李斯特菌生长动力学的孤立影响，即食品基质的性质、脂肪滴的存在和微生物生长形态。为此，使用了具有不同微观结构的基于鱼的模型系统，即液体、含有黄原胶的第二更粘稠的液体系统、乳液、水凝胶和凝胶化乳液。在 4 和 10°C 下进行了生长实验，均采用同质和表面接种（仅用于凝胶化系统）。关于生长形态影响的结果表明，在液体系统中浮游细胞的迟滞期与黄原胶系统中淹没菌落的迟滞期相似。在每个凝胶化系统中，淹没菌落的迟滞期比各自系统上表面菌落的迟滞期长得多。在 10°C 时，液体系统中浮游细胞的最大比生长速率明显低于黄原胶系统中淹没菌落的比生长速率，而在 4°C 时则没有观察到显著差异。最大细胞密度对于淹没菌落高于表面菌落。食品基质的性质仅对最大比生长速率有影响，在粘性系统中比在凝胶化系统中高得多。少量脂肪滴的存在提高了单核细胞增生李斯特菌在 4°C 下的生长，导致迟滞期缩短和最大比生长速率提高。获得的结果可用于确定一组适合的微观结构参数，以便在未来的预测模型中纳入食品微观结构对微生物动力学的影响。
