358 Modern Food Microbiology
100% CO 2 at 4 and 10
◦ C, it was dominated by Lactobacillus sakei/curvatus (92–96% of the biota)
after 30 days.
77 D-lactate increased more under CO 2 and vacuum than it did in aerobically stored products. The authors concluded that CO 2 had no significant effect on extending the self-life of taverna
sausage.
Overall, the low-temperature storage of fresh meats under vacuum or MAP is very satisfactory. This
is in large part a reflection of the existence of lactic acid and related bacteria on fresh meats, and when
these products are stored under low O 2 and high CO 2 conditions at low temperatures, the normal biota
prevents the growth of pathogens by virtue of depressed pH, competition for O 2 , possible production
of antimicrobial substances, and other factors.
Poultry
The effectiveness of MAP for the storage of fresh poultry was demonstrated in the early 1950s
73
and since that time a number of studies have been reported. Hotchkiss
48 used from 60% to 80% CO 2
on raw poultry in glass jars and found an increase in self-life to at least 35 days at 2
◦ C. In another
study, when high-barrier film (oxygen transmission rate [OTR] ca. 18 ml) was used to pack cut-up or
whole chicken that was held at 5
◦ C, the chicken had lower numbers of bacteria and kept longer than
that which was stretch-wrapped with a film that had an OTR of 6,500 ml, and this is illustrated in
Figure 14–2.
58 With poultry stored in air, the aerobic plate count (APC) of drip after 16 days at 10
◦ C
was 9.40 log 10 , whereas in 20% CO 2 the APC was 6.14 log 10 .
92
Overall, the generally higher initial pH of fresh poultry meat is primarily responsible for this
product’s not having the MAP self-life of products such as fresh beef.
Seafoods
MAP/vacuum packaging has been shown to extend the self-life of cod fillets, red snapper, rainbow
trout, herrings, mackerel, sardines, catfish, and others. In 1933, F.P. Coyne of England was apparently
the first person to show the preservative effects of CO 2 on fish (see reference 73).
For fish, using 80% CO 2 + air, log numbers after 14 days at 35
◦ C were approximately 6.00/cm
2
compared to air controls with log 10 numbers >10.5 cm
2 . The pH of CO 2 -stored products after 14
days decreased from around 6.75 to around 6.30, whereas controls increased to around 7.45.
74 The
self-life of rockfish and salmon at 4.5
◦ C was extended by 20–80% CO 2 .
8 At least 1 log difference in
bacterial counts over controls was obtained when trout and croaker were stored in CO 2 environments
at 4
◦ C.
39 When fresh shrimp or prawns were packed in ice with an atmosphere of 100% CO 2 , they
were edible for up to 2 weeks, and bacterial counts after 14 days were lower than air-packed controls
after 7 days.
64 When cod fillets were stored at 2
◦ C, air-stored samples spoiled in 6 days, with APC of
log 10 7.7, whereas samples stored in 50% CO 2 + 50% O 2 or 50% CO 2 + 50% N 2 or 100% CO 2 did
not show bacterial spoilage until, respectively, 26, 34, and 34 days, with respective APCs of 7.2, 6.6,
and 5.5 log 10 /g.
88 It was suggested that the use of 50% CO 2 + 50% O 2 is technically more feasible
than the use of 100% CO 2 . Whereas the practical upper limit of CO 2 for red meats is around 20%,
higher concentrations can be used with fish because they contain lower levels of myoglobin.
When salmon fillets were packaged in 60% CO 2 :40% N 2 and stored at −2
◦ C and 4
◦ C for 24 days,
the product stored at −2
◦ C was good for 24 days based on sensory and microbial analyses while that
stored in air had a 21-day sensory shelf-life.
83 The MAP fillets stored at 4
◦ C spoiled after 10 days
while those stored in air spoiled in 7 days. The overall sensory quality of the fillets was not adversely
affected by storage under MAP.
83
100% CO 2 at 4 and 10
◦ C, it was dominated by Lactobacillus sakei/curvatus (92–96% of the biota)
after 30 days.
77 D-lactate increased more under CO 2 and vacuum than it did in aerobically stored products. The authors concluded that CO 2 had no significant effect on extending the self-life of taverna
sausage.
Overall, the low-temperature storage of fresh meats under vacuum or MAP is very satisfactory. This
is in large part a reflection of the existence of lactic acid and related bacteria on fresh meats, and when
these products are stored under low O 2 and high CO 2 conditions at low temperatures, the normal biota
prevents the growth of pathogens by virtue of depressed pH, competition for O 2 , possible production
of antimicrobial substances, and other factors.
Poultry
The effectiveness of MAP for the storage of fresh poultry was demonstrated in the early 1950s
73
and since that time a number of studies have been reported. Hotchkiss
48 used from 60% to 80% CO 2
on raw poultry in glass jars and found an increase in self-life to at least 35 days at 2
◦ C. In another
study, when high-barrier film (oxygen transmission rate [OTR] ca. 18 ml) was used to pack cut-up or
whole chicken that was held at 5
◦ C, the chicken had lower numbers of bacteria and kept longer than
that which was stretch-wrapped with a film that had an OTR of 6,500 ml, and this is illustrated in
Figure 14–2.
58 With poultry stored in air, the aerobic plate count (APC) of drip after 16 days at 10
◦ C
was 9.40 log 10 , whereas in 20% CO 2 the APC was 6.14 log 10 .
92
Overall, the generally higher initial pH of fresh poultry meat is primarily responsible for this
product’s not having the MAP self-life of products such as fresh beef.
Seafoods
MAP/vacuum packaging has been shown to extend the self-life of cod fillets, red snapper, rainbow
trout, herrings, mackerel, sardines, catfish, and others. In 1933, F.P. Coyne of England was apparently
the first person to show the preservative effects of CO 2 on fish (see reference 73).
For fish, using 80% CO 2 + air, log numbers after 14 days at 35
◦ C were approximately 6.00/cm
2
compared to air controls with log 10 numbers >10.5 cm
2 . The pH of CO 2 -stored products after 14
days decreased from around 6.75 to around 6.30, whereas controls increased to around 7.45.
74 The
self-life of rockfish and salmon at 4.5
◦ C was extended by 20–80% CO 2 .
8 At least 1 log difference in
bacterial counts over controls was obtained when trout and croaker were stored in CO 2 environments
at 4
◦ C.
39 When fresh shrimp or prawns were packed in ice with an atmosphere of 100% CO 2 , they
were edible for up to 2 weeks, and bacterial counts after 14 days were lower than air-packed controls
after 7 days.
64 When cod fillets were stored at 2
◦ C, air-stored samples spoiled in 6 days, with APC of
log 10 7.7, whereas samples stored in 50% CO 2 + 50% O 2 or 50% CO 2 + 50% N 2 or 100% CO 2 did
not show bacterial spoilage until, respectively, 26, 34, and 34 days, with respective APCs of 7.2, 6.6,
and 5.5 log 10 /g.
88 It was suggested that the use of 50% CO 2 + 50% O 2 is technically more feasible
than the use of 100% CO 2 . Whereas the practical upper limit of CO 2 for red meats is around 20%,
higher concentrations can be used with fish because they contain lower levels of myoglobin.
When salmon fillets were packaged in 60% CO 2 :40% N 2 and stored at −2
◦ C and 4
◦ C for 24 days,
the product stored at −2
◦ C was good for 24 days based on sensory and microbial analyses while that
stored in air had a 21-day sensory shelf-life.
83 The MAP fillets stored at 4
◦ C spoiled after 10 days
while those stored in air spoiled in 7 days. The overall sensory quality of the fillets was not adversely
affected by storage under MAP.
83