Effect of relevant environmental factors for food preservation and molecular identification (High Resolution Melting) of Bacillus cereus group

Abstract

Bacteria are present in almost all foodstuffs determining their safety and shelf life. Depending on several factors such as processing, preservation techniques and storage conditions different microorganisms can be present in food. Among all of them, Bacillus cereus group species, which may cause spoilage and gastrointestinal diseases, are commonly isolated from different products due to their metabolic diversity and their ability to form highly resistant endospores. Members of this group have been reported to contaminate a large number of sources including raw, manufactured, refrigerated and dehydrated foods as well as from hot dairy equipment and industrial surfaces. In recent years, the development and implementation of consumer driven mild preservation techniques have become more popular in order to minimize the damage of the sensorial and nutritional properties of the food. However, this may further enhance the spore survival, and thus the persistence of spore formers in food production environments. Besides, recent studies pointed to mildly treated products stored at low temperature as an appropriate niche for B. cereus psychrotrophic strains and mesophilic strains able to grow below 10ºC. On this ground, and with the major aim to contribute to improve food preservation systems that ensure microbiological quality and avoid economical losses derived from spoilage, the present thesis deals with the study of the impact of relevant environmental factors, commonly referred as hurdles, on the survival and grow of different species of B. cereus group, as well as with the assessment of feasibility of novel methods for genotyping and for viability studies at single cell level.