Download Freeman 1e: How we got there

CHAPTER 29
Food Preservation and Foodborne
Microbial Diseases
Food Preservation and
Microbial Growth
Microbial Growth and Food
Spoilage
• 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).
• 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.
• A variety of microorganisms induce food
spoilage, and some food spoilage
microorganisms are also potential pathogens
(Table 29.2).
Food Preservation
• Food microbiology deals with methods for
limiting spoilage and the growth of diseasecausing microorganisms in food during
processing and storage.
• Foods vary considerably in their sensitivity
to microbial growth, depending on their
nutrient content, water availability, and pH.
• The growth of microorganisms in perishable
foods can be controlled by refrigeration, freezing,
lyophilization (freeze-drying), canning,
pickling, dehydration, chemical preservation
(Table 29.3), or irradiation (Table 29.4).
Fermented Foods
• 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).
Microbial Sampling and Food
Poisoning
Foodborne Diseases and
Microbial Sampling
• 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.
• Table 29.6 gives annual foodborne disease
estimates for the United States.
Staphylococcal Food Poisoning
• 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.
Clostridial Food Poisoning
• 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.
• Botulism is a rare but very serious disease,
with significant mortality (Figure 29.6).
Food Infection
Salmonellosis
• 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.
Pathogenic Escherichia coli
• 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.
• Large-scale processing methods for meats
and meat products allow contaminants from a
small number of individual carcasses to
contaminate or infect large numbers of
products.
Campylobacter
• Campylobacter infection is by far the most
prevalent foodborne bacterial infection.
Though usually self-limiting, this disease
affects nearly 2 million people per year.
Listeriosis
• 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.
Other Foodborne Infectious
Diseases
• 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.