This course will focus on food spoilage caused by microorganisms. The goal is to provide educational material for all microbiologists, especially students in the field, who will find explanations on the origins, consequences, and prevention methods for microbial spoilage flora. The document will shed light on the various types of commercial food spoilage, different hygiene indicators, and the flora responsible for collective food poisoning. This will cover taxonomic, pathophysiological, and epidemiological aspects, as well as various methods of prophylaxis. The main mycotoxins contaminating food and their mode of action will also be described. Finally, the main parasitic foodborne illnesses (where certain stages can be microscopic), microscopic algae transmitted through food, and some viral foodborne illnesses will be presented.