104 Modern Food Microbiology
log 10 4/g. The biota of vacuum-packaged sliced bacon consists largely of catalase-positive cocci, such
as micrococci and coagulase-negative staphylococci, as well as catalase-negative bacteria of the lactic
acid types, such as lactobacilli, leuconostocs, pediococci, and enterococci.
3,13,59 The biota in cooked
salami has been found to consist mostly of lactobacilli.
So-called soul foods may be expected to contain large numbers of organisms, as they consist of offal
parts that are in direct contact with the intestinal-tract biota, as well as other parts, such as pig feet
and pig ears, that do not receive much care during slaughtering and processing. This was confirmed
in a study by Stewart
86 who found a geometric mean aerobic plate count (APC) of log 10 7.92/g for
chitterlings (pig intestines), log 10 7.51/g for maws, and log 10 7.32/g for liver pudding. For S. aureus,
log 10 numbers of 5.18, 5.70, and 5.15/g, respectively, were found for chitterlings, maws, and liver
pudding.
Jerky is a dried shelf-stable product made from lightly salted and spiced slices of meat or fish—most
often beef. When drying to reduce a w to or below 0.86 is carried out within 3 hours, no problems
are likely to result from pathogens, but when drying is not rapid and extends over a long period of
time at temperatures <60
◦ C, S. aureus can survive.
49 In 1993, beef jerky was the vehicle food in
New Mexico for 93 cases of salmonellosis caused by three serovars—S. Montevideo, Kentucky, and
Typhimurium.
14 The product was produced in a commercial establishment, but it is unclear how it
became contaminated. To reduce a w to 0.86 during jerky processing, it has been found that a period
of 2.5–3.0 hours of drying at 52.9
◦ C is needed.
50 This is not lethal to foodborne pathogens, but it
would make the product stable to the growth of Staphylococcus aureus in the case of post-processing
contamination. For beef jerky, a period of 10 hours of drying at 60
◦ C has been shown capable of
reducing E. coli 0157:H7, L. monocytogenes, and Salmonella serovar Typhimurium by log 10 5.5–6.0
units.
42 In an evaluation of homestyle dehydrators, it was found that in order to achieve a log 10
5 reduction of E. coli 0157:H7, the following relation needed to be observed: about 20 hours of drying
at 125
◦ F, about 12 hours at 135
◦ F, about 8 hours at 145
◦ F, or 4 hours at 155
◦ F.
11 This organism was
more sensitive in meat with 5% fat than with 20%. For example, for jerky with 5% fat, a log 5 reduction
could be achieved in about 8 hours at 125
◦ F (51.7
◦ C).
From 32,800 packages of frankfurters examined by the FDA in the United States, L. monocytogenes
was recovered from 532 (1.6%) and about 90% of all isolates were serotype 1/2a.
96 In an extensive
study of luncheon meats for L. monocytogenes in the states of Maryland and California, the organism
was found in 82 of 9,199 or 0.89%.
38
Spoilage
Spoilage of these products is generally of three types: sliminess, souring, and greening. Slimy
spoilage occurs on the outside of casings, especially of frankfurters, and may be seen in its early
stages as discrete colonies, which may later coalesce to form a uniform layer of gray slime. Yeasts,
lactic acid bacteria of the genera Lactobacillus, Enterococcus, Weissella, and B. thermosphacta, may
be isolated from the slimy material. W. viridescens produces both sliminess and greening. Slime
formation is favored by a moist surface and is usually confined to the outer casing. Removal of this
material with hot or warm water leaves the product essentially unchanged.
Souring generally takes place underneath the casing of these meats and results from the growth of
lactobacilli, enterococci, and related organisms. The usual sources of these organisms to processed
meats are milk solids. The souring results from the utilization of lactose and other sugars by the
organisms and the production of acids. Sausage usually contains a more varied biota than most other
processed meats due to the different seasoning agents employed, almost all of which contribute their
log 10 4/g. The biota of vacuum-packaged sliced bacon consists largely of catalase-positive cocci, such
as micrococci and coagulase-negative staphylococci, as well as catalase-negative bacteria of the lactic
acid types, such as lactobacilli, leuconostocs, pediococci, and enterococci.
3,13,59 The biota in cooked
salami has been found to consist mostly of lactobacilli.
So-called soul foods may be expected to contain large numbers of organisms, as they consist of offal
parts that are in direct contact with the intestinal-tract biota, as well as other parts, such as pig feet
and pig ears, that do not receive much care during slaughtering and processing. This was confirmed
in a study by Stewart
86 who found a geometric mean aerobic plate count (APC) of log 10 7.92/g for
chitterlings (pig intestines), log 10 7.51/g for maws, and log 10 7.32/g for liver pudding. For S. aureus,
log 10 numbers of 5.18, 5.70, and 5.15/g, respectively, were found for chitterlings, maws, and liver
pudding.
Jerky is a dried shelf-stable product made from lightly salted and spiced slices of meat or fish—most
often beef. When drying to reduce a w to or below 0.86 is carried out within 3 hours, no problems
are likely to result from pathogens, but when drying is not rapid and extends over a long period of
time at temperatures <60
◦ C, S. aureus can survive.
49 In 1993, beef jerky was the vehicle food in
New Mexico for 93 cases of salmonellosis caused by three serovars—S. Montevideo, Kentucky, and
Typhimurium.
14 The product was produced in a commercial establishment, but it is unclear how it
became contaminated. To reduce a w to 0.86 during jerky processing, it has been found that a period
of 2.5–3.0 hours of drying at 52.9
◦ C is needed.
50 This is not lethal to foodborne pathogens, but it
would make the product stable to the growth of Staphylococcus aureus in the case of post-processing
contamination. For beef jerky, a period of 10 hours of drying at 60
◦ C has been shown capable of
reducing E. coli 0157:H7, L. monocytogenes, and Salmonella serovar Typhimurium by log 10 5.5–6.0
units.
42 In an evaluation of homestyle dehydrators, it was found that in order to achieve a log 10
5 reduction of E. coli 0157:H7, the following relation needed to be observed: about 20 hours of drying
at 125
◦ F, about 12 hours at 135
◦ F, about 8 hours at 145
◦ F, or 4 hours at 155
◦ F.
11 This organism was
more sensitive in meat with 5% fat than with 20%. For example, for jerky with 5% fat, a log 5 reduction
could be achieved in about 8 hours at 125
◦ F (51.7
◦ C).
From 32,800 packages of frankfurters examined by the FDA in the United States, L. monocytogenes
was recovered from 532 (1.6%) and about 90% of all isolates were serotype 1/2a.
96 In an extensive
study of luncheon meats for L. monocytogenes in the states of Maryland and California, the organism
was found in 82 of 9,199 or 0.89%.
38
Spoilage
Spoilage of these products is generally of three types: sliminess, souring, and greening. Slimy
spoilage occurs on the outside of casings, especially of frankfurters, and may be seen in its early
stages as discrete colonies, which may later coalesce to form a uniform layer of gray slime. Yeasts,
lactic acid bacteria of the genera Lactobacillus, Enterococcus, Weissella, and B. thermosphacta, may
be isolated from the slimy material. W. viridescens produces both sliminess and greening. Slime
formation is favored by a moist surface and is usually confined to the outer casing. Removal of this
material with hot or warm water leaves the product essentially unchanged.
Souring generally takes place underneath the casing of these meats and results from the growth of
lactobacilli, enterococci, and related organisms. The usual sources of these organisms to processed
meats are milk solids. The souring results from the utilization of lactose and other sugars by the
organisms and the production of acids. Sausage usually contains a more varied biota than most other
processed meats due to the different seasoning agents employed, almost all of which contribute their