690 Part VII: Food Safety
have the name of their company show up in a news
report as the source of a foodborne illness. Apart
from the loss of consumer confidence and loss of
sales, there are also legal aspects about which food
companies must be concerned (Odumeru 2002). An
estimated 76 million cases of foodborne illness per
year occur in the United States, resulting in 325,000
hospitalizations and 5000 deaths (Mead et al. 1999).
The economic impact of these illnesses is estimated
at $5 billion or more. A number of food safety pro-
grams are currently in place in the food industry in an
attempt to reduce the incidence of foodborne illness,
which has been on the rise in the last two decades
(Maurice 1994). The increase in the incidence of food-
borne disease has been attributed to a combination of
factors. These include changes in food production and
processing practices, changes in retail distribution,
social changes including consumerpreferences and
eating habits, lack of experience of mass kitchen per-
sonnel, changes in population demographics, and
increases in population mobility worldwide as a
result of increases in international trade and travel
(McMeekin and Olley 1995, Baird Parker 1994).
Furthermore, advances in sciences in the area of ana-
lytical methods development has led to the availabil-
ity of better detection methods for the diagnosis of
foodborne illness and a subsequent increase in the
number of cases reported. Other factors such as bet-
ter reporting systems and increases in the occurrence
of emerging pathogens have contributed to the
increase in cases of foodborne diseases reported.
Issues related to emerging pathogens will be dis-
cussed in a subsection of this chapter. A number of
scientific tools are now available to the food industry
and food safety regulators for implementing food
safety programs designed to reduce the incidence of
foodborne illness. These include the use of risk
assessment of foods and food ingredients, to deter-
mine the risks associated with various types of foods
under certain processing conditions; predictive mod-
eling, which estimates the growth and survival of
pathogens and spoilage organisms under specified
conditions; and rapid methods for screening foods
for quality and safety during and after production.
This chapter will provide an overview of issues relat-
ed to microbial safety of food and food products,
food preservation technologies, emerging pathogens,
food safety programs to control microbial contami-
nation, and future perspectives on food safety.
SHELF LIFE OF FOODS AND
FOOD INGREDIENTS AND FOOD
SAFETYThe shelf life of a food product generally refers to
the keeping quality of the food. An estimated 25%
of the food supplies worldwide are lost as a result of
spoilage; hence, it is economically beneficial to
maintain the quality of food products at various
stages of food production and storage. There are two
categories of foods in relation to shelf life: shelf sta-
ble and perishable. Whether a particular food prod-
uct is shelf stable or perishable depends on the
intrinsic properties of the food (e.g., pH, water activ-
ity, and structure). Shelf-stable foods usually have
low water activity, low pH, or a combination of both,
while perishable foods tend to have high water ac-
tivity and high pH. The structure or texture of the
food is also an important factor in shelf stability.
Extrinsic factors such as storage temperature, gas-
eous atmosphere, and relative humidity also deter-
mine the shelf stability of food products (McMeekin
and Ross 1996). These intrinsic and extrinsic factors
influence the survival and growth not only of spoil-
age organisms but also of pathogenic organisms in
foods. Food spoilage occurs as a result of physical or
chemical changes in the food or of the by-products
of spoilage microorganisms growing in the food
product. Pathogens present in low levels may not
produce identifiable changes in the food; hence, the
presence of pathogens cannot be determined using
noticeable changes in the food as an indicator.
Although shelf-stable foods are less likely to be
implicated in foodborne illness than perishable
foods, cross-contamination of shelf-stable or perish-
able foods by pathogens can be a source of food-
borne illness. A number of preservation applications
used in the food industry are designed to extend the
shelf life of the food product by reducing microbial
growth; however, pathogens that are able to survive
or even grow under preservation techniques such as
refrigeration can cause foodborne illness. Effective
strategies for controlling the presence of spoilage
and foodborne pathogens in foods should include
elimination of sources of contamination combined
with food preservation technologies such as drying,
freezing, smoking, curing, fermenting, refrigeration
(Baird-Parker 2000) and modified-atmosphere pack-
aging (Farber 1991)