Processed Meats and Seafoods
111
In their study of 91 samples of shrimp of various types, Silverman et al.
84 found that all precooked
samples except one had total counts of
peeled shrimp, 52% had total counts
The general microbiological quality of a variety of seafood is presented in Table 5–6.
In a study of haddock fillets, most microbial contamination was found to occur during filleting and
subsequent handling prior to packaging.
70 These investigators showed that the total count increased
from log 10 5.61/g in the morning to log 10 5.65/g at noon and to log 10 5.94/g in the evening for one
particular processor. According to their study, results obtained in other companies were generally
similar if the night time cleanup was good. In the case of shucked, soft-shell clams, the same general
pattern of buildup was demonstrated from morning to evening. The mean clostridial count for both
haddock fillets and soft-shell clams was less than 2/g, with clams having slightly higher counts than
haddock fillets for these organisms, although both were low. Total counts on fresh perch fillets produced
under commercial conditions were found to average log 10 5.54/g with yeast and mold counts of about
log 10 2.69/g.
58
Clams may be expected to contain the organisms that inhabit the waters from which they are
obtained. Of 60 clam samples from the coast of Florida, 43% contained salmonellae, which were also
found in oysters at a level of 2.2/100 g oyster meats.
33 Hard-shell clams have been shown to retain S.
Typhimurium more efficiently than E. coli.
33
The initial biota of herring fillets has been found to be dominated by S. putrefaciens and Pseudomonas spp., with the latter dominating at 2
◦ C and S. putrefaciens more predominant at 2–15
◦ C.
69
In general, frozen seafood and other frozen products have lower microbial counts than the comparable
fresh products. In a study of 597 fresh and frozen seafood from retail stores, the APC log 10 geometric
means ranged from 3.54 to 4.97/g for the 240 frozen products and from 4.89 to 8.43/g for the 357
fresh products.
32 For coliforms, geometric mean MPN counts ranged from 1 to 7.7 cells/g for frozen
and from 7.78 to 4,800/g for fresh products. By MPN, only 4.7% of the 597 were positive for E.
coli, 7.9% were positive for S. aureus, and 2% were positive for C. perfringens. All were negative for
salmonellae and Vibrio parahaemolyticus (Table 5–6).
Plate counts are generally higher on seafood when incubated at 30
◦ C than at 35
◦ C, and this is
reflected in results from fresh crabmeat, clams, and oysters, evaluated by Wentz et al.
100 The APC
geometric means were: for 896 crabmeat samples, log 10 5.15 at 35
◦ C and log 10 5.72 at 30
◦ C; for 1,337
shucked oysters, log 10 5.59/g at 35
◦ C and log 10 5.95 at 30
◦ C; and for 358 soft-shell clams, log 10 2.83/g
at 35
◦ C and log 10 4.43 at 30
◦ C. This was also seen in raw in-shell shrimp and frozen raw lobster tails,
where the geometric mean APC for shrimp was log 10 5.48 at 35
◦ C and log 10 5.90/g at 30
◦ C, whereas
for lobster tail, it was log 10 4.62 at 35
◦ C and log 10 5.15/g at 30
◦ C.
89
In a study of the prevalence of aeromonads on catfish, 228 channel catfish fillets from three processing
plants in the Mississippi Delta were examined, and both A. hydrophila and A. sobria were found on
36% while A. caviae was found on 11%.
97 Most of the two predominant species produced alpha
hemolysis on sheep red blood cells. In a study of the biota of catfish processing equipment in two
plants, Aeromonas and Pseudomonas spp. were the most abundant genera found.
22
Between 1995 and 1998, a 3-year monthly study of viral contamination of 108 oysters and 73 mussels
for four groups of viruses was conducted in southern France. Results showed that virus concentrations
generally were highest during the cold months (November to March) but variations were seen with
different viruses.
61 Rotaviruses showed no seasonal distribution but varied from month to month with
July being the month with the lowest prevalence as was the case for enteroviruses and astroviruses.
The peak for noroviruses was November; and December and January were the peak months for the
other three groups with at least 70% of samples being positive during the peaks.
111
In their study of 91 samples of shrimp of various types, Silverman et al.
84 found that all precooked
samples except one had total counts of
peeled shrimp, 52% had total counts
The general microbiological quality of a variety of seafood is presented in Table 5–6.
In a study of haddock fillets, most microbial contamination was found to occur during filleting and
subsequent handling prior to packaging.
70 These investigators showed that the total count increased
from log 10 5.61/g in the morning to log 10 5.65/g at noon and to log 10 5.94/g in the evening for one
particular processor. According to their study, results obtained in other companies were generally
similar if the night time cleanup was good. In the case of shucked, soft-shell clams, the same general
pattern of buildup was demonstrated from morning to evening. The mean clostridial count for both
haddock fillets and soft-shell clams was less than 2/g, with clams having slightly higher counts than
haddock fillets for these organisms, although both were low. Total counts on fresh perch fillets produced
under commercial conditions were found to average log 10 5.54/g with yeast and mold counts of about
log 10 2.69/g.
58
Clams may be expected to contain the organisms that inhabit the waters from which they are
obtained. Of 60 clam samples from the coast of Florida, 43% contained salmonellae, which were also
found in oysters at a level of 2.2/100 g oyster meats.
33 Hard-shell clams have been shown to retain S.
Typhimurium more efficiently than E. coli.
33
The initial biota of herring fillets has been found to be dominated by S. putrefaciens and Pseudomonas spp., with the latter dominating at 2
◦ C and S. putrefaciens more predominant at 2–15
◦ C.
69
In general, frozen seafood and other frozen products have lower microbial counts than the comparable
fresh products. In a study of 597 fresh and frozen seafood from retail stores, the APC log 10 geometric
means ranged from 3.54 to 4.97/g for the 240 frozen products and from 4.89 to 8.43/g for the 357
fresh products.
32 For coliforms, geometric mean MPN counts ranged from 1 to 7.7 cells/g for frozen
and from 7.78 to 4,800/g for fresh products. By MPN, only 4.7% of the 597 were positive for E.
coli, 7.9% were positive for S. aureus, and 2% were positive for C. perfringens. All were negative for
salmonellae and Vibrio parahaemolyticus (Table 5–6).
Plate counts are generally higher on seafood when incubated at 30
◦ C than at 35
◦ C, and this is
reflected in results from fresh crabmeat, clams, and oysters, evaluated by Wentz et al.
100 The APC
geometric means were: for 896 crabmeat samples, log 10 5.15 at 35
◦ C and log 10 5.72 at 30
◦ C; for 1,337
shucked oysters, log 10 5.59/g at 35
◦ C and log 10 5.95 at 30
◦ C; and for 358 soft-shell clams, log 10 2.83/g
at 35
◦ C and log 10 4.43 at 30
◦ C. This was also seen in raw in-shell shrimp and frozen raw lobster tails,
where the geometric mean APC for shrimp was log 10 5.48 at 35
◦ C and log 10 5.90/g at 30
◦ C, whereas
for lobster tail, it was log 10 4.62 at 35
◦ C and log 10 5.15/g at 30
◦ C.
89
In a study of the prevalence of aeromonads on catfish, 228 channel catfish fillets from three processing
plants in the Mississippi Delta were examined, and both A. hydrophila and A. sobria were found on
36% while A. caviae was found on 11%.
97 Most of the two predominant species produced alpha
hemolysis on sheep red blood cells. In a study of the biota of catfish processing equipment in two
plants, Aeromonas and Pseudomonas spp. were the most abundant genera found.
22
Between 1995 and 1998, a 3-year monthly study of viral contamination of 108 oysters and 73 mussels
for four groups of viruses was conducted in southern France. Results showed that virus concentrations
generally were highest during the cold months (November to March) but variations were seen with
different viruses.
61 Rotaviruses showed no seasonal distribution but varied from month to month with
July being the month with the lowest prevalence as was the case for enteroviruses and astroviruses.
The peak for noroviruses was November; and December and January were the peak months for the
other three groups with at least 70% of samples being positive during the peaks.