Thermal Food Processing

Thermal Processing of Meat Products 179
TABLE 6.6
Typical Thermal Destruction Parameters for
Common Food-Borne Pathogens
Pathogen and Substrate
Thermal Destruction Parameters
D60°C (min) Z (°C)
L. monocytogenes
Lean ground beef 2.07 5.17
Fat ground beef 3.29 6.33
E. coli O157:H7
Lean ground beef 1.97 4.67
Fat ground beef 1.20 4.61
Salmonella spp.
Lean ground beef 2.21 5.56
Fat ground beef 1.58 5.56
C. perfringens
Lean ground beef 5.30 6.74
Since the objective is to eliminate the most heat resistant microorganisms in
the product, it should be recognized that several factors influence the heat resistance
of those microorganisms. Microbial factors include strain, source, and
previous exposure to stress. 1,47 Intrinsic factors in the food matrix that influence
heat sensitivity include media, fat content, pH, and water activity. 47 Sometimes,
development of resistance to a given set of factors may cause cross-resistance to
other affecting factors, such as heat. 48 A summary of the heat resistance of
common foodborne pathogens is provided in Table 6.6.
Use of the terms “sterilization” and “pasteurization” in describing thermal
processes applied to foods refers to the basic purpose of the treatment to destroy
pathogenic microorganisms and those of spoilage types. The main difference lies
in the application of the heat and the severity of the treatment. Pasteurization is
the term most often applied to describe processes that are relatively mild, and to
destroy vegetative pathogenic microorganisms in a food product. Sterilization is
the term used to describe a more severe heat treatment, e.g., those given to lowacid
canned foods that are designed to destroy virtually all microorganisms,
regardless of heat resistance.
However, these severe heat treatments may result in products with unacceptable
quality, and are often used in moderation to destroy microorganisms or spores
of microorganisms of public health significance, such as C. botulinum, C. perfringens,
and B. cereus. The implication is that these milder heat treatments may
result in survival of the more heat resistant spore types, such as B. stearothermophilus,
B. subtilis, and similar spore formers. Their growth in the food products
during subsequent storage and distribution is restricted due to either product
intrinsic characteristics, such as pH, a w, etc., or the storage conditions, such as