Processed Meats and Seafoods
105
own biota. B. thermosphacta has been found by many investigators to be the most predominant spoilage
organism for sausage.
The changes that fresh meat bacteria bring about as processed meats undergo souring are unlikely to
occur in the latter since many members of the fresh meat Gram-negative biota are unable to proliferate
at the lower a w and pH of processed meats. Even in fresh meats, definitive spoilage changes affecting
structural proteins do not occur until APC is in the 10
9 to 10
10 range
54 .
Although mold spoilage of these meats is not common, it can and does occur under favorable
conditions. When the products are moist and stored under conditions of high humidity, they tend to
undergo bacterial and yeast spoilage. Mold spoilage is likely to occur only when the surfaces become
dry or when the products are stored under other conditions that do not favor bacteria or yeasts.
Two types of greening occur on stored and processed red meats: one caused by H 2 O 2 and the
other by H 2 S. The former occurs commonly on frankfurters as well as on other cured and vacuumpackaged meats. It generally appears after an anaerobically stored meat product is exposed to air.
Upon exposure to air, H 2 O 2 forms and reacts with nitrosohemochrome to produce a greenish oxidized porphyrin.
73 H 2 O 2 may accumulate when heating if nitrite destroys catalase, and the peroxide
reacts with meat pigments to form choleglobin, which is green. Greening also occurs from growth
of causative organisms in the interior core, where the low oxidation–reduction (Eh) potential allows
H 2 O 2 to accumulate. Weissella viridescens is the most common organism in this type of greening, but
leuconostocs, Enterococcus faecium, and Enterococcus faecalis are capable of producing greening
of products. Greening can also be produced by H 2 O 2 producers such as Lactobacillus fructivorans
and Lactobacillus jensenii. W. viridescens is resistant to >200 ppm NaNO 2 , and it can grow in
the presence of 2–4% NaCl but not in 7%.
73 W. viridescens has been recovered from anaerobically
spoiled frankfurters and from both smoked pork loins and frankfurter sausage stored in atmospheres
of CO 2 and N 2 .
8 In spite of the discoloration, the green product is not known to be harmful if
eaten.
The second type of greening occurs generally on fresh red meats that are held at 1–5
◦ C and stored
in gas-impermeable or vacuum-packaging containers; it is caused by H 2 S production. H 2 S reacts
with myoglobin to form sulphmyoglobin (Table 5–2). This type of greening does not usually occur
when meat pH is below 6.0. The organism responsible in one study was thought to be Pseudomonas
mephitica
71 but in another study of DFD meats, S. putrefaciens was the H 2 producer.
37 In the latter,
greening occurred even with glucose present, and it could be prevented by lowering pH to below 6.0.
H 2 S-producing lactobacilli were recovered from vacuum-packaged fresh beef and found to produce
H 2 S in the pH range of 5.4–6.5.
81 Only slight greening was produced, and the H 2 S was from cysteine,
a system that was plasmid borne. The organism reached 3 × 10
7 /cm
2 after 7 days, and ultimately
reached about 10
8 /cm
2 at 50
◦ C. No offness of vacuum-packaged sliced luncheon meat was observed
when another lactobacillus attained 10
8 /cm
2 .
At least one strain of Lactobacillus sakei has been shown to produce H 2 S on vacuum-packaged
beef; and the effect of pH and glucose on production is presented in Table 5–3.
26 The investigators
found that greening by L. sakei was not as intense as that caused by S. putrefaciens and that it occurred
only after about 6 weeks at 0
◦ C. Further, the lactobacillus produced H 2 S only in the absence of O 2
and utilizable sugars. No greening was observed when films with an O 2 transmission rate of 1 ml
O 2 /m
2 or 300 ml O 2 /m
2 were used, but it did occur with films that had O 2 transmission rates between
25 and 200 ml/m
2 /24 hours.
26 Visible greening was seen only on samples packaged in films with O 2
transmission rates of 100 and 200 ml/m
2 /24 hours and only after 75 days’ storage. With meat in the
pH 6.4–6.6 range, H 2 S was detected when cell numbers reached 10
8 /g.
A yellow discoloration of vacuum-packaged luncheon-style meat was caused apparently by Enterococcus casseliflavus. The discoloration appeared as small spots on products stored at 4.4
◦ C, and
105
own biota. B. thermosphacta has been found by many investigators to be the most predominant spoilage
organism for sausage.
The changes that fresh meat bacteria bring about as processed meats undergo souring are unlikely to
occur in the latter since many members of the fresh meat Gram-negative biota are unable to proliferate
at the lower a w and pH of processed meats. Even in fresh meats, definitive spoilage changes affecting
structural proteins do not occur until APC is in the 10
9 to 10
10 range
54 .
Although mold spoilage of these meats is not common, it can and does occur under favorable
conditions. When the products are moist and stored under conditions of high humidity, they tend to
undergo bacterial and yeast spoilage. Mold spoilage is likely to occur only when the surfaces become
dry or when the products are stored under other conditions that do not favor bacteria or yeasts.
Two types of greening occur on stored and processed red meats: one caused by H 2 O 2 and the
other by H 2 S. The former occurs commonly on frankfurters as well as on other cured and vacuumpackaged meats. It generally appears after an anaerobically stored meat product is exposed to air.
Upon exposure to air, H 2 O 2 forms and reacts with nitrosohemochrome to produce a greenish oxidized porphyrin.
73 H 2 O 2 may accumulate when heating if nitrite destroys catalase, and the peroxide
reacts with meat pigments to form choleglobin, which is green. Greening also occurs from growth
of causative organisms in the interior core, where the low oxidation–reduction (Eh) potential allows
H 2 O 2 to accumulate. Weissella viridescens is the most common organism in this type of greening, but
leuconostocs, Enterococcus faecium, and Enterococcus faecalis are capable of producing greening
of products. Greening can also be produced by H 2 O 2 producers such as Lactobacillus fructivorans
and Lactobacillus jensenii. W. viridescens is resistant to >200 ppm NaNO 2 , and it can grow in
the presence of 2–4% NaCl but not in 7%.
73 W. viridescens has been recovered from anaerobically
spoiled frankfurters and from both smoked pork loins and frankfurter sausage stored in atmospheres
of CO 2 and N 2 .
8 In spite of the discoloration, the green product is not known to be harmful if
eaten.
The second type of greening occurs generally on fresh red meats that are held at 1–5
◦ C and stored
in gas-impermeable or vacuum-packaging containers; it is caused by H 2 S production. H 2 S reacts
with myoglobin to form sulphmyoglobin (Table 5–2). This type of greening does not usually occur
when meat pH is below 6.0. The organism responsible in one study was thought to be Pseudomonas
mephitica
71 but in another study of DFD meats, S. putrefaciens was the H 2 producer.
37 In the latter,
greening occurred even with glucose present, and it could be prevented by lowering pH to below 6.0.
H 2 S-producing lactobacilli were recovered from vacuum-packaged fresh beef and found to produce
H 2 S in the pH range of 5.4–6.5.
81 Only slight greening was produced, and the H 2 S was from cysteine,
a system that was plasmid borne. The organism reached 3 × 10
7 /cm
2 after 7 days, and ultimately
reached about 10
8 /cm
2 at 50
◦ C. No offness of vacuum-packaged sliced luncheon meat was observed
when another lactobacillus attained 10
8 /cm
2 .
At least one strain of Lactobacillus sakei has been shown to produce H 2 S on vacuum-packaged
beef; and the effect of pH and glucose on production is presented in Table 5–3.
26 The investigators
found that greening by L. sakei was not as intense as that caused by S. putrefaciens and that it occurred
only after about 6 weeks at 0
◦ C. Further, the lactobacillus produced H 2 S only in the absence of O 2
and utilizable sugars. No greening was observed when films with an O 2 transmission rate of 1 ml
O 2 /m
2 or 300 ml O 2 /m
2 were used, but it did occur with films that had O 2 transmission rates between
25 and 200 ml/m
2 /24 hours.
26 Visible greening was seen only on samples packaged in films with O 2
transmission rates of 100 and 200 ml/m
2 /24 hours and only after 75 days’ storage. With meat in the
pH 6.4–6.6 range, H 2 S was detected when cell numbers reached 10
8 /g.
A yellow discoloration of vacuum-packaged luncheon-style meat was caused apparently by Enterococcus casseliflavus. The discoloration appeared as small spots on products stored at 4.4
◦ C, and