INFLUENCE OF SUBSTRATE STRUCTURE ON BACTERIAL GROWTH

摘要

Food products are highly complex systems. As food safety is of great importance for food scientists, several tools have been developed in order to control it including the concept of Predictive Microbiology. So far, in most Predictive Microbiology studies the growth of microorganisms has been studied in liquid, homogenous growth media, where microbial cells are free, displaying a planktonic growth pattern. However, real foods are solid (or semi-solid) structured systems. In order to understand the way that microorganisms grow in real food systems, food microstructure has to be investigated as well as the way that this microstructure interacts with microorganisms. The objective of this research was the local study of microstructure and its influence on bacterial growth. Particularly, the goals were: (i) the investigation of gelling systems of hydrocolloids and (ii) the evaluation of the influence of each system on the growth of Listeria monocytogenes. A series of experiments were performed with gels that have been prepared and inoculated with the pathogen in which growth kinetics were studied. Alginates and gelatin were used at different concentrations. The results of this study showed that structure affects the growth of the pathogen and any increase in the hydrocolloid concentration results in a decrease in the growth rate. However, it has to be pointed out that each system affects pathogen's growth in a different way. The results of this study could be used in order to incorporate the parameter of structure in predictive models, as the influence of structure and immobilization of bacterial cells on microbial proliferation are really important for Predictive Microbiology.