Thermal Food Processing

Thermal Processing of Poultry Products 217
surveillance statistics, Todd 90 reported that contaminated meat products were linked
to more outbreaks of food-borne disease (i.e., 16%) in the U.S. than all other food
product categories. Of the 22 countries surveyed, France and Spain were the only
two nations to report that eggs and egg products were the vehicles most frequently
involved in outbreaks of food-borne illness.
7.3.2.1 Salmonella
Of the above-listed pathogens, Salmonella species have the greatest historical
association with contaminated eggs and egg products. The bacterial pathogens L.
monocytogenes and A. hydrophila pose particular concerns if present in chilled
liquid egg products due to their ability to multiply in foods at proper refrigerated
storage temperatures (i.e., 5°C). Over the last decade, the egg-associated serotype
S. Enteritidis has emerged as one of the leading causes of food-borne salmonellosis
in the U.S., Canada, the U.K., France, Spain, and other nations. 90 In the U.S., the
number of cases of salmonellosis caused by S. Enteritidis increased slowly but
steadily between 1976 and 1987. Since 1988, the isolation rate for S. Enteritidis
from clinical cases of salmonellosis has risen sharply, possibly as a result of this
serotype becoming more invasive in egg-laying flocks. 91 Since 1990, the number
of salmonellosis cases caused by S. Enteritidis have exceeded those attributed to
all other serovars, including S. Typhimurium. 92 Epidemiological studies indicate
that grade A shell eggs are a major source of S. Enteritidis infections in humans. 93
Between January 1985 and May 1987, 35 food-borne S. Enteritidis outbreaks of
known cause were reported to the CDC; of these, 27 outbreaks (77%) were
epidemiologically linked to the consumption of foods that contained eggs or eggs
alone, either inadequately cooked or eaten raw in such foods as hollandaise sauce,
homemade eggnog, or Caesar salad dressing. 93 Between 1985 and 1991, a total
of 380 S. Enteritidis outbreaks were reported in the U.S., involving 13,056 cases
and 50 deaths. Grade A shell eggs were implicated in 82% of the outbreaks. 94
Without question, the implementation of the Egg Products Inspection Act of
1970 and its accompanying liquid egg pasteurization requirements has dramatically
reduced the incidence of egg-associated salmonellosis in the U.S. 95 The use
of pasteurized liquid egg products (rather than shell eggs) for the preparation of
a variety of egg dishes is viewed as the major means for preventing salmonellosis
outbreaks, especially in food service settings and nursing homes. 69 When pasteurized
liquid egg products are properly packaged, stored, and handled by food
preparers, egg-associated risks of salmonellosis may be significantly reduced. To
date, no salmonellosis outbreaks in the U.S., England, or Wales have been associated
with foods containing pasteurized liquid egg. 96
7.3.2.1.1 Thermal Resistance of Salmonella in Eggs
and Egg Products
Because liquid egg pasteurization processes were designed to ensure inactivation
of Salmonella, numerous investigators have sought to define the thermal inactivation
kinetics of this important pathogen. 67,96 The conventional pasteurization process for