production and to eliminate disease prob-
lems in dairy cows has contributed to more
wholesome dairy products, although con-
tamination can occur from the udders of
cows and milking equipment. The subse-
quent pasteurization in processing plants has
further reduced milkborne disease microor-
ganisms. Nevertheless, dairy products are
vulnerable to cross-contamination from
items that have not been pasteurized.
Because not all dairy products are pasteur-
ized, the presence of pathogens (especially
Listeria monocytogenes) in this industry has
increased. (Additional discussion related to
contamination of dairy products is pre-
sented in Chapter 16.)
Red Meat Products
The muscle tissues of healthy living ani-
mals are nearly free of microorganisms.
Contamination of meat occurs from the
external surface, such as hair, skin, and the
gastrointestinal and respiratory tracts. The
animal’s white blood cells and the antibod-
ies developed throughout their lives effec-
tively control infectious agents in the living
body. These internal defense mechanisms
are destroyed when blood is removed dur-
ing harvesting.
Initial microbial inoculation of meat
results from the introduction of microor-
ganisms into the vascular system when
contaminated knives are used for exsan-
guination. The vascular system rapidly dis-
seminates these microorganisms throughout
the body. Contamination subsequently
occurs by the introduction of microorgan-
isms on the meat surfaces in operations per-
formed during slaughtering, cutting,
processing, storage, and distribution of
meat. Other contamination can occur by
contact of the carcass with the hide, feet,
manure, dirt, and visceral contents from
punctured digestive organisms.
Poultry Products
Poultry is vulnerable to contamination espe-
cially SalmonellaandCampylobacterorgan-
isms during processing. The processing of
poultry, especially defeathering and eviscera-
tion, permits an opportunity for the distribu-
tion of microorganisms among carcasses.
Contaminated hands and gloves and other
tools of processing plant workers also con-
tribute to the transmission of salmonellae.Seafood Products
Seafoods are excellent substrates for
microbial growth and are vulnerable to con-
tamination during harvesting, processing,
distribution, and marketing. They are excel-
lent sources of proteins and amino acids,
B vitamins, and a number of minerals
required in bacterial nutrition. Seafoods are
handled extensively from harvesting to con-
sumption. Because they are frequently stored
for long periods of time without prior refrig-
eration, contamination and growth of
spoilage microorganisms and microbes of
public health concern can occur. (Chapter 18
provides additional discussion related to
seafood contamination.)Adjuncts:
Ingredients (especially spices) are potential
vehicles of harmful or potentially harmful
microorganisms and toxins. The amounts
and types of these agents vary with place and
method of harvesting, type of food ingredi-
ent, processing technique, and handling. The
food plant management team should be
aware of the hazards connected with individ-
ual incoming ingredients. Only supplies and
materials gathered in accordance with recog-
nized good practices should be used. This
requirement also applies to control of testing
of critical materials, either by the manufac-
turing firm, receiving establishment, or both.Food Contamination Sources 79