Food-Service-Manual-for-Health-Care-Institutions

Food Service Manual for Health Care Institutions
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(bitter) foods have a pH above 7.0, which can support the growth of bacteria that cause foodborne
illnesses. Such food materials include those of animal origin (such as meat, poultry,
seafood, eggs, and milk) and low-acid vegetables (such as corn, peas, beets, and beans). Acids
such as vinegar are used in food preservation to slow down bacterial growth and, in some
cases, can be used in food preparation to inhibit bacterial growth. For example, commercial
mayonnaise is acidic enough to suppress bacterial growth in salad mixtures when it is added
early in the preparation process. Acidity also increases the sensitivity of bacteria to heat. For
example, low-acid vegetables must be treated at a higher temperature and for a longer time in
the canning process than is required for high-acid fruits.
Many bacteria prefer a neutral environment (pH of 7.0) but are capable of growing in
foods that have a pH range of 4.6 to 9.0. Disease-causing bacteria grow best when the food
they live on has a pH of 4.6 to 7.0; such foods include milk, fish, and meat. As the pH increases
or decreases, the organisms adjust to their surroundings and then start growing again but more
slowly. Some foods are naturally acidic (vinegar, pickles, fruits). At a pH of 4.6 (acidic) or
below, organisms grow slowly or not at all.
Inhibitors
Many naturally occurring or manufactured chemicals, called inhibitors, can be used to prevent
or slow down bacterial growth. For example, sodium nitrite (which is used in the curing of
bacon, ham, and sausage) is effective in preventing the growth of C. botulinum (the organism
that causes botulism) even at low levels of concentration.
Time
Bacterial multiplication takes place over time. How rapidly bacteria grow depends on environmental
conditions, including those factors already described. In food service operations, the
objective is to keep foods at the recommended temperatures and under sanitary conditions for
the recommended periods to prevent bacterial growth. Foods requiring refrigeration after
preparation must be cooled rapidly to an internal temperature of 41°F (5°C) or lower. Large
quantities of such foods need to be cooled in shallow pans, under quick-chilling refrigeration,
or by cold-water circulation around the food container. The cooling time needed to reach 41°F
(5°C) should be no more than four hours (140°F to 70°F, two hours, and to 41°F, four hours).
On the other hand, cold foods should be heated as rapidly as possible to an internal temperature
of 165°F (74°C) or higher and should be held at that temperature for no more than two
hours.
Viruses
Viruses, another type of microorganism, are defined as noncellular organisms consisting of
nucleic acids and protein that reproduce in host cells. They are the smallest and perhaps the
simplest form of life and are a concern of food service managers because, unlike bacteria,
viruses do not multiply outside a living cell in food products and are not complete cells. Once
viruses enter a living cell, they force the cell to stop its life processes and to assist in producing
more viruses.
Sources of food-borne outbreak or water-borne viral disease include contaminated water
supply, food handled by an infected employee who failed to follow correct personal hygiene
practices, and, if eaten raw, molluscan shellfish (oysters, mussels, and clams) harvested from
polluted water. The virus is found in urine and feces of infected persons and in contaminated
water.
Two viruses of particular concern to the food service operation are hepatitis A virus and
the Norwalk virus (discussed later in this chapter under Emerging Pathogens). These viruses are
known to cause food-borne illness through poor personal hygiene practices.