BLBS102-c41 BLBS102-Simpson March 21, 2012 14:25 Trim: 276mm X 219mm Printer Name: Yet to Come
788 Part 8: Food Safety and Food Allergensthe rise in the last two decades (Maurice 1994). The increase
in the incidence of foodborne disease has been attributed to a
combination of factors. These include changes in food produc-
tion and processing practices, changes in retail distribution, so-
cial changes including consumer preferences and eating habits,
lack of experience of mass kitchen personnel, changes in popula-
tion demographics, and increases in population mobility world-
wide 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 analytical methods devel-
opment has led to the availability of better detection methods
for the diagnosis of foodborne illness and a subsequent increase
in the number of cases reported. Other factors such as better
reporting systems and increases in the occurrence of emerging
pathogens have contributed to the increase in cases of food-
borne diseases reported. Issues related to emerging pathogens
will be discussed 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 determine the risks associated with various types of foods un-
der certain processing conditions; predictive modeling, 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 produc-
tion. This chapter will provide an overview of issues related to
microbial safety of food and food products, food preservation
technologies, emerging pathogens, food safety programs to con-
trol microbial contamination, 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 world-
wide 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 stable and perishable.
Whether a particular food product is shelf stable or perishable
depends on the intrinsic properties of the food (e.g., pH, wa-
ter activity, and structure). Shelf-stable foods usually have low
water activity, low pH, or a combination of both, while per-
ishable foods tend to have high water activity and high pH.
The structure or texture of the food is also an important factor
in shelf stability. Extrinsic factors such as storage temperature,
gaseous atmosphere, and relative humidity also determine the
shelf stability of food products (McMeekin and Ross 1996).
These intrinsic and extrinsic factors influence the survival and
growth not only of spoilage 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 perishable foods by pathogens can be a source of
foodborne 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 tech-
niques such as refrigeration can cause foodborne illness. Effec-
tive strategies for controlling the presence of spoilage and food-
borne pathogens in foods should include elimination of sources
of contamination combined with food preservation technologies
such as drying, freezing, smoking, curing, fermenting, refriger-
ation (Baird-Parker 2000) and modified-atmosphere packaging
(Farber 1991).CATEGORIES OF FOODBORNE
ORGANISMSMicroorganisms that can be transmitted to humans or animals
through food are referred to as foodborne organisms. There
are three main categories of foodborne organisms: spoilage,
pathogenic, and beneficial. 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 en-
zymes released by spoilage organisms can result in deteriora-
tion of food quality. Growth of microorganisms to high numbers
is usually required before spoilage becomes noticeable. Hence,
control of growth of spoilage organisms is required to impede
microbial spoilage. The presence of foodborne pathogens in
foods in low concentrations can render foods harmful to hu-
mans 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
consumption of contaminated foods. “Beneficial” or “useful”
organisms include microorganisms used in various food fermen-
tation processes. These organisms 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 bene-
ficial 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 bac-
teria. These includeLactococcus, Leuconostoc, Streptococcus,
Lactobacillus, Pediococcus, Carnobacterium, Tetragenococcus,
Aerococcus, Vagococcus,andEnterococcus.The most important
type of yeast used for fermentation of food and alcohol isSac-
charomyces cerevisiae.This yeast is used for leavening bread
and production of beer, wine, and liquors. It is also used for food
flavor. Non-mycotoxin-producing molds from the generaPeni-
cilliumandAspergillus,and some in theRhizopusandMucor
genera, have been used for beneficial purposes in food prepara-
tion (Bibek 1996).