Thermal Food Processing

170 Thermal Food Processing: New Technologies and Quality Issues
Epidemiologic surveillance data indicate that the case fatality rate varies by age,
with a higher case fatality rate among newborns and the elderly.
L. monocytogenes can be in the food processing environment and can form
biofilms on solid surfaces commonly found in food processing plants, including
stainless steel and rubber under experimental conditions. Listeria can also survive
adverse conditions on apparently smooth surfaces. Recently, several recalls of readyto-eat
(RTE) meat and poultry products have occurred because of adulteration with
L. monocytogenes. Food-borne illnesses and deaths have been linked to some recalled
products. It has generally been concluded that the adulteration occurred through
cross-contamination from environmental sources following cooking.
6.5.2.4 Clostridium perfringens
C. perfringens is widely distributed in a variety of foods, particularly meat and
poultry, and has been implicated in numerous food-borne disease outbreaks. The
abilities of C. perfringens to form heat-resistant spores and grow at a very rapid
rate at relatively high temperatures are the major contributing factors leading to
food poisoning. The temperature range for growth of C. perfringens, 6 to 52.3°C
is well documented. 20,31 A short generation time of 7.1 min in ground beef means
that after the spores have germinated, rapid cooling of foods is critical. 1,32,33
C. perfringens continues to be a concern to the food industry, particularly to
the retail and food service industries, and has been implicated in several large
outbreaks. The U.S. Centers for Disease Control and Prevention estimates more
than 248,000 cases of food-borne illness due to C. perfringens annually in the U.S. 30
Although C. perfringens vegetative cells do not survive the normal heat
processing schedules employed in the meat industry, the spores can survive. Heatactivated
spores can germinate and grow rapidly if these products are improperly
chilled. Juneja and coworkers 1,32,33 reported D 58°C values of 1.15 to 1.60 min for
10 strains of C. perfringens (vegetative cells) in a model beef gravy system, which
are similar to the D values reported for vegetative food-borne pathogens such as
E. coli O157:H7, Salmonella spp., and L. monocytogenes. 29,34 Lethality standards
for Salmonella spp. 27,28 should be adequate to control normal incidence levels of
C. perfringens vegetative cells in processed meat and poultry products.
In case thermal process deviations (heating or cooling) occur, spores of C.
perfringens, if present in the raw meats utilized for processing of cooked products
may be heat activated, germinate, and grow to hazardous levels during cooling
or improper storage. The time/temperature guidelines for cooling cooked products
specify that the maximum internal temperature should not remain between 54.4
and 26.7°C for more than 1.5 h, nor between 26.7 and 4.4°C for more than 5 h. 28
The U.S. Food and Drug Administration (FDA) Division of Retail Food Protection
recognized that inadequate cooling was a major food safety problem and established
a recommendation that all food should be cooled from 60 to 21°C in 2 h
and from 21 to 5°C in 4 h. 35 Of importance is the use of organic acid antimicrobials
such as lactates, diacetates, and citrates, which have been shown to act as
bacteriostats to prevent outgrowth of activated spores. 36 A complete compilation