Conventionally, all food products can be divided into "breathing" (with biochemical metabolic activity) and "non-breathing". The former include vegetables, fruits, fresh plant materials, rennet cheeses, and fresh meat. The second group includes ready-made and chilled dishes, ready-made meat products, dairy products, canned food, pasta, baked goods, and cereals.
Freshly picked fruits and vegetables absorb oxygen and release carbon dioxide, water, heat and volatiles. They "breathe" according to the scheme: C6H12O6 + 6O2 = 6CO2 + 6H2O + 674 kcal. Inside the package, this process takes place under the condition of free access of oxygen and removal of end products, primarily carbon dioxide (CO2).
"Breathable" products are packed in materials with increased gas permeability. The "non-breathing" is preserved by vacuum packing, removing oxygen from it. The product is placed in a bag and, after removing air from it, is hermetically sealed. This is how fresh meat and meat products, fish, poultry, bakery, confectionery and other perishable goods are usually packaged.