Fresh Meats and Poultry
73
of these being Y. enterocolitica, 25% Y. kristensenii, 15% Y. intermedia, and 9% Y. frederiksenii. In a
study of 43 pork samples from a slaughterhouse, eight contained the following yersiniae species: Y.
enterocolitica, Y. intermedia, Y. kristensenii, and Y. frederiksenii.
82 From a study of hogs in the United
States, 95 of 103 (92%) lots carried at least one Y. enterocolitica isolate, and 99% of the pathogenic
isolates were serotype 0:5, and 3.7% were 0:3.
61 In Finland, 92% of 51 tongue and 25% of 255 ground
meat samples contained Y. enterocolitica.
57 By using PCR and a culture method, >98% of the pork
tongues were positive with biotype IV being the most common. From 31 pork tongues from freshly
slaughtered animals, 21 strains were isolated with 0:8 being the most common, and 0:6, 30 the next
most common.
38 A study of yersiniae in raw beef and chicken in Brazil revealed that 80% contained
these organisms with ground beef and liver accounting for 60% and pork for 20%.
183
In a study of the fate of Yersinia enterocolitica in a Turkish dry sausage (sucuk), the pathogen
decreased from around 5.0 to 1.8 log 10 cfu after 4 days of fermentation and to 0.5 log 10 cfu/g after
12 days of drying without the direct addition of lactic acid bacteria.
25 With the addition of about 7.0
log 10 cfu/g each of Lactobacillus sakei and Pediococcus acidilactici, the pathogen was reduced to 0.5
log 10 cfu/g after 3 days of fermentation, and none was detectable after 4 days.
25
Pathogenic Escherichia coli Strains
E. coli 0157:H7 on red meats and poultry varies widely with none being found on 990 samples of
boneless beef to 17% for two red meats (Table 4–7). The 296 ground beef and cattle fecal samples were
taken from the Seattle, WA area (where the 1993 ground beef outbreak occurred). Of non-0157:H7
Stx-producing strains isolated by Brooks et al.,
16 the most common serovar was 0128:H2, which
produced both Stx1 and 2 toxins, along with three others. No 0157:H7 strains were found in this study
of 218 samples.
In large and medium diameter Lebanon-style bologna, a 5-log reduction of E. coli 0157:H7 was
achieved during the smoking process.
69 The fermentation process consisted of 8 hr at 26.7
◦ C, then 24
h at 37.8
◦ C, and finally 24 h at 43.3H
◦ C, all internal temperatures. The starting material had a pH of
4.4 with 4.0% NaCl and low fat (10–13%), and it was inoculated with E. coli 0157:H7 at a level of
7.5 to 7.9 log 10 cfu/g.
69
Soy-Extended Ground Meats
The addition of soy protein (soybean flour, soy flakes, texturized soy protein) at levels of 10–30%
to ground meat patties is fairly widespread in the fast-food industry, at least in the United States, and
the microbiology of these soy blends has been investigated. The earliest, most detailed study is that of
Craven and Mercuri
30 who found that when ground beef or chicken was extended with 10% or 30%
soy, APCs of these products increased over unextended controls when both were stored at 4
◦ C for up
to 8–10 days. Whereas coliforms were also higher in beef-soy mixtures than in controls, this was not
true for the chicken-soy blends. In general, APCs were higher at the 30% level of soy than at 10%.
In one study in which 25% soy was used with ground beef, the mean time to spoilage at 4
◦ C for the
beef-soy blend was 5.3 days compared to 7.5 days for the unextended ground beef.
14 In another study
using 10%, 20%, and 30% soy, the APC increased significantly with both time and concentration of
soy in the blend.
97
With regard to the microbiological quality of soy products, the geometric mean APC of 1,226 sample
units of seasoned product was found to be 1,500/g, with fungi, coliforms, E. coli, and Staphylococcus
aureus, counts of 25, 3, 3, and 10/g, respectively.
171
73
of these being Y. enterocolitica, 25% Y. kristensenii, 15% Y. intermedia, and 9% Y. frederiksenii. In a
study of 43 pork samples from a slaughterhouse, eight contained the following yersiniae species: Y.
enterocolitica, Y. intermedia, Y. kristensenii, and Y. frederiksenii.
82 From a study of hogs in the United
States, 95 of 103 (92%) lots carried at least one Y. enterocolitica isolate, and 99% of the pathogenic
isolates were serotype 0:5, and 3.7% were 0:3.
61 In Finland, 92% of 51 tongue and 25% of 255 ground
meat samples contained Y. enterocolitica.
57 By using PCR and a culture method, >98% of the pork
tongues were positive with biotype IV being the most common. From 31 pork tongues from freshly
slaughtered animals, 21 strains were isolated with 0:8 being the most common, and 0:6, 30 the next
most common.
38 A study of yersiniae in raw beef and chicken in Brazil revealed that 80% contained
these organisms with ground beef and liver accounting for 60% and pork for 20%.
183
In a study of the fate of Yersinia enterocolitica in a Turkish dry sausage (sucuk), the pathogen
decreased from around 5.0 to 1.8 log 10 cfu after 4 days of fermentation and to 0.5 log 10 cfu/g after
12 days of drying without the direct addition of lactic acid bacteria.
25 With the addition of about 7.0
log 10 cfu/g each of Lactobacillus sakei and Pediococcus acidilactici, the pathogen was reduced to 0.5
log 10 cfu/g after 3 days of fermentation, and none was detectable after 4 days.
25
Pathogenic Escherichia coli Strains
E. coli 0157:H7 on red meats and poultry varies widely with none being found on 990 samples of
boneless beef to 17% for two red meats (Table 4–7). The 296 ground beef and cattle fecal samples were
taken from the Seattle, WA area (where the 1993 ground beef outbreak occurred). Of non-0157:H7
Stx-producing strains isolated by Brooks et al.,
16 the most common serovar was 0128:H2, which
produced both Stx1 and 2 toxins, along with three others. No 0157:H7 strains were found in this study
of 218 samples.
In large and medium diameter Lebanon-style bologna, a 5-log reduction of E. coli 0157:H7 was
achieved during the smoking process.
69 The fermentation process consisted of 8 hr at 26.7
◦ C, then 24
h at 37.8
◦ C, and finally 24 h at 43.3H
◦ C, all internal temperatures. The starting material had a pH of
4.4 with 4.0% NaCl and low fat (10–13%), and it was inoculated with E. coli 0157:H7 at a level of
7.5 to 7.9 log 10 cfu/g.
69
Soy-Extended Ground Meats
The addition of soy protein (soybean flour, soy flakes, texturized soy protein) at levels of 10–30%
to ground meat patties is fairly widespread in the fast-food industry, at least in the United States, and
the microbiology of these soy blends has been investigated. The earliest, most detailed study is that of
Craven and Mercuri
30 who found that when ground beef or chicken was extended with 10% or 30%
soy, APCs of these products increased over unextended controls when both were stored at 4
◦ C for up
to 8–10 days. Whereas coliforms were also higher in beef-soy mixtures than in controls, this was not
true for the chicken-soy blends. In general, APCs were higher at the 30% level of soy than at 10%.
In one study in which 25% soy was used with ground beef, the mean time to spoilage at 4
◦ C for the
beef-soy blend was 5.3 days compared to 7.5 days for the unextended ground beef.
14 In another study
using 10%, 20%, and 30% soy, the APC increased significantly with both time and concentration of
soy in the blend.
97
With regard to the microbiological quality of soy products, the geometric mean APC of 1,226 sample
units of seasoned product was found to be 1,500/g, with fungi, coliforms, E. coli, and Staphylococcus
aureus, counts of 25, 3, 3, and 10/g, respectively.
171