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CHAPTER 29 Food Preservation and Foodborne Microbial Diseases. Food Preservation and Microbial Growth Microbial Growth and Food Spoilage.
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Food Preservation and Foodborne Microbial Diseases
Foods often spoil due to growth of contaminating microorganisms. Foods vary considerably in their sensitivity to microbial growth, depending on their nutrient value and water activity (aw) (Table 29.1).
A variety of microorganisms induce food spoilage, and some food spoilage microorganisms are also potential pathogens (Table 29.2).
Perishable and semiperishable foods have limited shelf life due to spoilage. Nonperishable (stable) foods have an extended shelf life and are resistant to spoilage by microorganisms.
Food microbiology deals with methods for limiting spoilage and the growth of disease-causing microorganisms in food during processing and storage.
Microbial fermentation is an important process used to preserve and enhance a number of foods, including breads, dairy products, meats, and vegetables (Table 29.5).
Foodborne diseases include food poisoning and food infection. Food poisoning results from the action of microbial toxins, and food infections result from the growth of microorganisms in the body. Specialized techniques are used to sample microorganisms in food.
Staphylococcal food poisoning results from the ingestion of preformed enterotoxin, a superantigen produced by Staphylococcus aureus when growing in foods. In many cases, S. aureus cannot be cultured from the contaminated food.
Clostridium food poisoning results from ingestion of toxins produced by microbial growth in foods or by microbial growth and toxin production in the body. Perfringens food poisoning is quite common and is usually a self-limiting gastrointestinal disease.
There are more than 1.3 million cases of salmonellosis every year in the United States (Figure 29.7). The disease results from infection with ingested Salmonella introduced into the food chain from food production animals or food handlers.
Enteropathogenic Escherichia coli can cause serious food infections. Specific measures, such as radiation of ground beef, have been implemented to curb the spread of these pathogens.
Campylobacter infection is by far the most prevalent foodborne bacterial infection. Though usually self-limiting, this disease affects nearly 2 million people per year.
Listeria monocytogenes is an environmentally ubiquitous microorganism. In normal individuals, Listeria seldom causes infection. However, in immunocompromised individuals, Listeria can cause serious disease and even death.
More than 200 different infectious agents cause foodborne disease. Viruses cause the vast majority of foodborne illnesses. A number of bacteria, protozoans, and prions also cause foodborne illnesses.