352 Modern Food Microbiology
Table 14–1 Synopsis of the Early History of Use of Modified-Atmospheres and Related
Technologies
Year
Event
1882 Elevated levels of CO 2 were shown to extend the storage life of meats for 4 to 5 weeks.
1889 The antibacterial activity of CO 2 was established
1895 Lopriore observed that 100% CO 2 inhibited the germination of mold spores
1910 Modified-atmosphere packaging was quite widely used to preserve certain foods
1938 About 26% of New Zealand and 60% of Australian beef was shipped under CO 2 atmospheres
1960 The hypobaric system was outlined by S. Burg
1972 The Tectrol process was introduced in the United States for long-distance transportation of
meats, poultry, and seafoods
1972 A cryogenic O 2 –N 2 atmosphere (liquid O 2 –N 2 ) system was patented by the Union Carbide
Corporation
1976 The Grumman Corporation built the Dormavac, a hypobaric highway storage container based
on Burg’s hypothesis
Vacuum Packaging
By this method, air is evacuated from gas-impermeable pouches followed by sealing. This has the
effect of reducing the residual air pressure from the usual 1 bar to 0.3–0.4 bar, hence some O 2 is
removed (1 bar = 0.9869 atm). Upon storage of a vacuum-packaged food product, an increase in CO 2
occurs as a result of both tissue and microbial respiration where O 2 is consumed and CO 2 is released
in equal volumes. In the case of meats, up to 10–20% CO 2 may develop within four hours and the
concentration may ultimately reach 30% from respiratory activities of the aerobic biota (Table 14–2).
A vacuum pack can be achieved by placing foods in high-barrier plastic pouches followed by the
evacuation of pouches under vacuum (10–745 mm Hg) and heat sealing or heat shrinking by dipping in
Table 14–2 Percentage of CO 2 and O 2 in Gas-Impermeable
Packages of Fresh Pork Stored between 3 Hours and 14 Days
at 2
◦ C and 16
◦ C
2
◦
C
1 6
◦
C
Storage Time
CO 2
O 2
CO 2
O 2
After 3 hours
3–5
20
3–5
—
After 4 days
13
20
30
1
After 5 days
—
—
30
1
After 10 days
15
1
—
—
After 14 days
15
1
—
—
Source: Adapted with permission from G.A. Gardner et al., 28 Bacteriology
of Prepacked Pork with Reference to the Gas Composition within the Pack,
Journal of Applied Bacteriology, Vol. 30, pp. 321–333, copyright c
1967,
Blackwell Scientific Publishers, Ltd.
Table 14–1 Synopsis of the Early History of Use of Modified-Atmospheres and Related
Technologies
Year
Event
1882 Elevated levels of CO 2 were shown to extend the storage life of meats for 4 to 5 weeks.
1889 The antibacterial activity of CO 2 was established
1895 Lopriore observed that 100% CO 2 inhibited the germination of mold spores
1910 Modified-atmosphere packaging was quite widely used to preserve certain foods
1938 About 26% of New Zealand and 60% of Australian beef was shipped under CO 2 atmospheres
1960 The hypobaric system was outlined by S. Burg
1972 The Tectrol process was introduced in the United States for long-distance transportation of
meats, poultry, and seafoods
1972 A cryogenic O 2 –N 2 atmosphere (liquid O 2 –N 2 ) system was patented by the Union Carbide
Corporation
1976 The Grumman Corporation built the Dormavac, a hypobaric highway storage container based
on Burg’s hypothesis
Vacuum Packaging
By this method, air is evacuated from gas-impermeable pouches followed by sealing. This has the
effect of reducing the residual air pressure from the usual 1 bar to 0.3–0.4 bar, hence some O 2 is
removed (1 bar = 0.9869 atm). Upon storage of a vacuum-packaged food product, an increase in CO 2
occurs as a result of both tissue and microbial respiration where O 2 is consumed and CO 2 is released
in equal volumes. In the case of meats, up to 10–20% CO 2 may develop within four hours and the
concentration may ultimately reach 30% from respiratory activities of the aerobic biota (Table 14–2).
A vacuum pack can be achieved by placing foods in high-barrier plastic pouches followed by the
evacuation of pouches under vacuum (10–745 mm Hg) and heat sealing or heat shrinking by dipping in
Table 14–2 Percentage of CO 2 and O 2 in Gas-Impermeable
Packages of Fresh Pork Stored between 3 Hours and 14 Days
at 2
◦ C and 16
◦ C
2
◦
C
1 6
◦
C
Storage Time
CO 2
O 2
CO 2
O 2
After 3 hours
3–5
20
3–5
—
After 4 days
13
20
30
1
After 5 days
—
—
30
1
After 10 days
15
1
—
—
After 14 days
15
1
—
—
Source: Adapted with permission from G.A. Gardner et al., 28 Bacteriology
of Prepacked Pork with Reference to the Gas Composition within the Pack,
Journal of Applied Bacteriology, Vol. 30, pp. 321–333, copyright c
1967,
Blackwell Scientific Publishers, Ltd.