Evaluation of (Micro)Structural-related Factors on Microbial Growth in/on Food-based Model Systems

Microbial growth is influenced by variations in intrinsic complexity of foods ((micro)structure, composition and physicochemical characteristics). So far, the effect of food (micro)structure has been assessed mainly by comparing planktonic growth in liquid (microbiological) media with colonial growth in/on solid-like systems or on real food surfaces. However, many foods are emulsions or gelled emulsions with complex intrinsic characteristics as compared to liquids or solids.

In this study, the effect of food (micro)structure on the dynamics of Listeria monocytogenes, Salmonella Typhimurium and Staphylococcus aureus, is investigated via food (model) systems with variable (micro)structural complexity, composition and physicochemical characteristics. The (micro)structures studied were: liquids, aqueous gels, emulsions and gelled emulsions. The composition and physicochemical characteristics of gelled emulsions targeted two different types of foods: (i) Frankfurter sausages and (ii) fish patés. All model systems were incubated at 4, 8 and 12°C and analysed for their pH and water activity values. The model systems approaching Frankfurters in composition were vacuum packed and analysed for their resistance to penetration.

This study illustrated the significance influence of food (micro)structure on microbial dynamics. Also, the maximum specific growth rate estimated on the collected experimental data was compared to the predictions of ComBase at the specific storage temperature and pH and a_w values of the different model systems. Further studies are required to fully quantify the interaction of food (micro)structure with other food intrinsic and extrinsic factors.