Human Food Chain and Microorganisms: A Case of Co-Evolution

The human food chain, from the raw materials to the human gut microbiota, can be regarded as a sequence of intercom-municating macro-and micro-ecosystems inhabited by more or less specialized microbial populations or consortia. The dynamics of development or selection of these different populations or individual species, including pathogens, spanned along the entire chain, as well as the effects of their metabolic activity on the food quality and safety, are matters of fundamental interest which involve also social and regulatory aspects. The borderlines of the well-known " reservoirs " or ecological niches of certain microbial species or ecotypes are destined to be widened. In fact the virtual human food chain tends to expand in time and space due to the extension of the products shelf life, the market globalization, the multiplicity of the geographic origin of the raw materials, which vehiculate pathogens and favor the spread of antibiotic resistant organisms. The diffusion of new thermal and non-thermal technological processes or new ingredients and the evolution of the distribution and consumption patterns require a continuous revision of the microbiological risk assessment. In fact, pathogen and spoilage organisms respond dynamically to their environment and its changes. Understanding their behavior is critical because of the evidence of increasing resistance to established sanitization and preservation techniques, and the increased use of minimal processes conditions, which are more vulnerable to the development of resistance. The evaluation of the risk in food safety requires prevision of the probability that microbial population sizes will not exceed defined levels at the consumption level (Food Safety Objectives). Predictive microbiology involves knowledge of the responses, in terms of survival, inactiva-tion and growth, to environmental factors summarized as equations or mathematical models. Coupled with information on environmental history during processing and storage, predictive microbiology provides information in making decisions on the microbiological safety and quality of foods. However, food systems are colonized by microbial communities, which comprise an interwoven matrix of biological diversity undergoing physical or chemical variations over space and time. Relatively little is known about their structure and function and pre-dictive modeling is limited by a dearth of comprehensive ecological principles that describe microbial community processes. During the last century the emphasis on the study of microbes in pure culture has isolated microorganisms from their communities and focused on their individual behavior in the biologically simple micro-environment of the experiment. Although these simple approaches have driven an explosion of knowledge …