Meats and poultry
The first commercial application of modified atmosphere preservation of meat was developed in the 1930s.
Based on scientific evidence, refrigerated beef carcasses were transported by ship from New Zealand and Australia to the UK in a carbon dioxideenriched environment.
However, MAP of retail-size meat packages was not introduced until the 1950s, in the form of vacuum packaging. Much later, in 1981, Marks & introduced a wide range of fresh meats in the market, packaged in gas-flushed plastic trays (Inns, 1987).
One of the main quality attributes of red meat, and an important indicator of product "freshness", is its color. The bright red color of fresh meat desired by consume is due to the presence ofoxymyoglobin, a myoglobin pigment in its oxygenated form.
Over time, however, oxymyoglobin gradually changes to metmyoglobin, which has an undesirable brownish color. Preservation of the desired bright red color can be achieved by packaging the meat in oxygen-enriched atmospheres.
Meat is a highly perishable food. and the major factor that limits its shelf life is microbial growth. It was noted earlier that carbon dioxide slows down the growth rate of microbes. Thus, atmospheres high in carbon dioxide should be used to suppress microbes and extend shelf life.
Consequently, MAP of meat in a gas mixture with high amounts of both oxygen and carbon dioxide is ideal for preserving the product's quality and extending its shelf life. The recommended atmosphere compositions for beef and pork are shown in Table 10.1.
In the case of poultry, me presence of oxygen is not necessary. Sometimes, such as in the case of turkey meat, the presence of oxygen may even be harmful because it causes off-flavours (Inns, 1987).
The shelf life of poultry products under MAP increases as the concentration of carbon dioxide in the atmosphere increases.
This is probably due to the suppression of microbial growth. However, it has been observed that using carbon dioxide in the gas mixture beyond a certain point results in product discoloration and has negative effects on shelf life.