it can also delay the development of oxidative rancidity. Oxygen is
included in the gas flush mixtures for the retail display of red meats to
maintain the bright red appearance of oxymyoglobin. This avoids the
acceptability problem associated with vacuum packs of red meats,
although the high oxygen concentration (typically 60–80%) helps offset
the inhibitory effect of he CO 2 (around 30%) so that the growth of
aerobes is slowed rather than suppressed entirely.
Incontrolled-atmosphere storage, CAP, the product environment is
maintained constant throughout storage. It is used mainly for bulk
storage and transport of foods, particularly fruits and vegetables, such
as the hard cabbages used for coleslaw manufacture. CAP is used for
shipment of chilled lamb carcasses and primal cuts which are packed in
an aluminium foil laminate bag under an atmosphere of 100% CO 2 .Itis
more commonly encountered though with fruits such as apples and pears
which are often stored at sub-ambient temperatures in atmospheres
containing around 10% CO 2. This has the effect of retarding mould
spoilage of the product through a combination of the inhibitory effect of
CO 2 on moulds and its ability to act as an antagonist to ethylene,
delaying fruit senescence and thus maintaining the fruit’s own ability to
resist fungal infection.
Table 4.13 MAP gas mixtures used with foods
Product % CO 2 %O 2 %N 2
Fresh meat 30 30 40
15–40 60–85 –
Cured meat 20–50 0 50–80
Sliced cooked roast beef 75 10 15
Eggs 20 0 80
0 0 100
Poultry 25–30 0 70–75
60–75 5–10 420
100 0 0
20–40 60–80 0
Pork 20 80 0
Processed meats 0 0 100
Fish (white) 40 30 30
Fish (oily) 40 0 60
60 0 40
Cheese (hard) 0–70 30–100
Cheese 0 0 100
Cheese; grated/sliced 30 0 70
Sanwiches 20–100 0–10 0–100
Pasta 0 0 100
70–80 0 20–30
Bakery 0 0 100
100 0 0
FromJ. Food Protection, 1991, 54 , 58–70, with permission
Chapter 4 111