food microbiology food microbiology food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. this includes the study of microorganisms causing food spoilage; pathogens that may cause disease (especially if food is improperly cooked or stored); microbes used to produce fermented foods such as cheese, yogurt, bread, beer, and wine; and microbes with other useful roles, such as producing probiotics. food safety terms foodborne illness good manufacturing practice (gmp) hazard analysis and critical control points (haccp) hazard analysis and risk-based preventive controls (harpc) critical control point critical factors fat tom ph water activity (aw) bacterial pathogens clostridium botulinum escherichia coli listeria salmonella vibrio cholerae cronobacter spp viral pathogens enterovirus hepatitis a norovirus rotavirus parasitic pathogens cryptosporidium entamoeba histolytica giardia trichinella subgroups of bacteria that affect food in the study of bacteria in food, important groups have been subdivided based on certain characteristics. these groupings are not of taxonomic significance: lactic acid bacteria are bacteria that use carbohydrates to produce lactic acid. the main genera are lactococcus, leuconostoc, pediococcus, lactobacillus and streptococcus thermophilus. acetic acid bacteria like acetobacter aceti produce acetic acid. bacteria such as propionibacterium freudenreichii that produce propionic acid are used to ferment dairy products. some clostridium spp. clostridium butyricum produce butyric acid. proteolytic bacteria hydrolyze proteins by producing extracellulat proteinases. this group includes bacteria species from the micrococcus, staphylococcus, bacillus, clostridium, pseudomonas, alteromonas, flavobacterium and alcaligenes genera, and more limited from enterobacteriaceae and brevibacterium. lipolytic bacteria hydrolyze triglycerides by production of extracellular lipases. this group includes bacteria species from the micrococcus, staphylococcus, pseudomonas, alteromonas and flavobacterium genera. saccharolytic bacteria hydrolyze complex carbohydrates. this group includes bacteria species from the bacillus, clostridium, aeromonas, pseudomonas and enterobacter genera. thermophilic bacteria are able to thrive in high temperatures above 50 celsius, including genera bacillus, clostridium, pediococcus, streptococcus, and lactobacillus. thermoduric bacteria, including spores, can survive pasteurization. bacteria that grow in cold temperatures below 5 celsius are called psychotropic and include bacteria species from many genera including alcaligenes, serratia, leuconostoc, carnobacterium, brochothrix, listeria and yersinia. halotolerant bacteria can survive high salt concentrations greater than 10%. this includes some species from vibrio and corynebacterium. aciduric bacteria survive at low ph. osmophilic bacteria, while less osmophilic than yeasts and molds, can tolerate a relatively higher osmotic environment. aerobes require oxygen, while anaerobes are inhibited by it. facultative anaerobes can grow with and without oxygen. some bacteria can produce gases during metabolism of nutrients, others produce slime by synthesizing polysaccharides. spore producing bacteria are further divided into subgroups of aerobic, anaerobic, flat sour, thermophilic and sulfide-producing. coliforms, including fecal coliforms (such as e.coli) are used as a measure of sanitation. enteric pathogens can cause gastrointestinal infection and may be included in this group. food safety a microbiologist working in a biosafety laboratory tests for high risk pathogens in food food safety is a major focus of food microbiology. numerous agents of disease and pathogens are readily transmitted via food which includes bacteria and viruses. microbial toxins are also possible contaminants of food; however, microorganisms and their products can also be used to combat these pathogenic microbes. probiotic bacteria, including those that produce bacteriocins can kill and inhibit pathogens. alternatively, purified bacteriocins such as nisin can be added directly to food products. finally, bacteriophages, viruses that only infect bacteria can be used to kill bacterial pathogens. thorough preparation of food, including proper cooking, eliminates most bacteria and viruses. however, toxins produced by contaminants may not be liable to change to non-toxic forms by heating or cooking the contaminated food due to other safety conditions. fermentation