For long-term preservation of the quality and freshness of food products, fruits and vegetables, packaging in a gas atmosphere (GVS) has been widely used in recent years.
Each product has an optimal ratio of oxygen, carbon dioxide and nitrogen, at which it is better stored. For example, an environment with a significant amount of oxygen (up to 80%) is suitable for raw meat. The bright red color of meat, an indicator of freshness, is provided by the oxymyoglobin contained in it, which, with a lack of oxygen, turns into metmyoglobin, the meat darkens, acquiring a non-marketable appearance.
Prepared meat products, sausages, smoked fish, cheeses, baked goods are better preserved with minimal or no oxygen. For cheeses, a gas medium containing 99% carbon dioxide and 1% oxygen is used. It is recommended to store fresh vegetables, fruits, berries, mushrooms in a gas environment with a reduced amount of oxygen (2-3%) and an increased amount of carbon dioxide (2-5%) compared to the usual composition of air.
The most common gas packages are those with a modified atmosphere (MAP) and a controlled atmosphere (RGM).
Modified gaseous medium (MGM) is characterized by the fact that an atmosphere is artificially created inside the package, which slows down the "breathing" of the product. This reduces the growth of microorganisms and putrefactive bacteria and increases the shelf life of packaged products by 2-3 times. This is how meat and fish dishes with side dishes, semi-finished products, salads, snacks, pastries, and various bakery products are packed and stored.
A controlled atmosphere (CGM) differs from CGM in that the composition of the gas mixture inside the package changes during storage of the product and depends on the degree of its "breathing" or other reasons. Here, perforated films, gas-selective or selective-permeable film membrane materials are used. Films with selective gas permeability are mainly suitable for fresh produce, vegetables and berries. Low temperature (to reduce "breathing") and special valves or membranes made of silicone gas-permeable materials also contribute to the best storage conditions. A silicone membrane is similar to a "window" in a film package. Oxygen, necessary for the "breathing" of the product, enters through it, and the resulting carbon dioxide comes out. This significantly increases the shelf life of products, especially vegetable products. Fruit, for example, is preserved from harvest to harvest with little or no change in quality. Recently, RGS has been used for portioned packaging of hard cheeses, because they belong to "breathing" products and emit substances that change the gas environment.