30 Microbial Safety of Food and Food Products 691CATEGORIES OF FOODBORNE
ORGANISMS
Microorganisms that can be transmitted to humans
or animals through food are referred to as foodborne
organisms. There are three main categories of food-
borne organisms: spoilage, pathogenic, and benefi-
cial. Spoilage organisms can grow and produce
physical and chemical changes in foods, resulting in
unacceptable flavor, odor, formation of slime, gas
accumulation, release of liquid exudates or purge,
and changes in consistency, color, and appearance.
Also, extracellular or intracellular enzymes released
by spoilage organisms can result in deterioration of
food quality. Growth of microorganisms to high
numbers is usually required before spoilage be-
comes noticeable. Hence, control of growth of spoil-
age organisms is required to impede microbial
spoilage. The presence of foodborne pathogens in
foods in low concentrations can render foods harm-
ful to humans if consumed. Because pathogenic
organisms at low levels may not produce noticeable
changes in foods, consumers may not have advance
warning signals of the danger associated with con-
sumption of contaminated foods. “Beneficial” or
“useful” organisms include microorganisms used in
various food fermentation processes. These organ-
isms are either naturally present in such foods or
added to produce the desired by-product of fer-
mentation. Various types of foods such as fruits and
vegetables, pickles, dairy products, meats, sausages,
cheeses, and yogurt are common types of fermented
products involving the use of beneficial organisms.
Beneficial organisms include organisms in the group
of lactic acid bacteria, yeasts, and molds. Bacteria
species from 10 genera are included in the group of
lactic acid bacteria. These include Lactococcus,
Leuconostoc, Streptococcus, Lactobacillus, Pedio-
coccus, Carnobacterium, Tetragenococcus, Aeroco-
ccus, Vagococcus,and Enterococcus.The most im-
portant type of yeast used for fermentation of food
and alcohol is Saccharomyces cerevisiae. This
yeast is used for leavening bread and production of
beer, wine, and liquors. It is also used for food fla-
vor. Non-mycotoxin-producing molds from the
genera Penicilliumand Aspergillus,and some in
the Rhizopusand Mucorgenera, have been used for
beneficial purposes in food preparation (Bibek
1996).
SOURCES OF FOODBORNE
PATHOGENSIn order to determine and implement effective con-
trol measures for pathogens in foods, it is important
to identify potential sources of contamination. Plants
and animals are the main source of human food sup-
ply. The exterior and, in some cases, the interior of
plants and animals harbor microorganisms from ex-
ternal sources such as soil, water, and air. These
environmental sources contain a wide variety of mi-
croorganisms, some of which are pathogenic to
man. Contamination of the food supply can occur at
various stages of production, processing, transporta-
tion, and storage. For example, fruits and vegetables
can be contaminated at the farm level as well as dur-
ing harvesting, transportation, and processing. Po-
tential sources of on-farm contamination of fruits
and vegetables are summarized in Figure 30.1.
Meats can be contaminated at the time of slaughter,
processing, and storage. Microbial contamination
can come from slaughtered animals, water, equip-
ment, utensils, the slaughterhouse environment, and
workers. Thus intervention strategies to control mi-
crobial contamination of the food supply must be
implemented at various stages of food production,
processing, transportation, and storage, and also at
the consumer end of food preparation.FOODBORNE DISEASE CASES
AND OUTBREAKSFoodborne disease in a susceptible host can result
from consumption of food or water contaminated
with pathogenic organisms. A single or sporadic
case of foodborne illness refers to an instance when
an illness that is unrelated to other cases occurs as a
result of consumption of contaminated food or
water. An outbreak, on the other hand, refers to an
incident in which two or more persons become ill
after consuming the same food or water from the
same source. The occurrence of a foodborne illness
depends on a number of risk factors such as (1) type
and number of pathogenic microorganisms in the
food, (2) effect of food product formulation or pro-
cessing on the viability of the pathogen, (3) storage
conditions of the food that may promote contami-
nation, growth, and survival of the pathogen, and
(4) the susceptibility of the individual to foodborne