Most of the fresh-keeping films and commonly used plastic bags sold in the market are made of ethylene masterbatch. According to the different types of ethylene masterbatch, the fresh-keeping films can be divided into three categories.
The first is polyethylene, or PE for short. This material is mainly used for food packaging. The film we usually buy for fruits and vegetables, including semi-finished products purchased in supermarkets, uses this material;
The second is polyvinyl chloride (PVC), which can also be used for food packaging, but it has a certain impact on human safety;
The third kind is polyvinylidene chloride (PVDC), which is mainly used for the packaging of some cooked food, ham and other products.
Among the three kinds of fresh-keeping films, PE and PVDC fresh-keeping films are safe for human body and can be safely used. However, PVC fresh-keeping films contain carcinogens and are harmful to human body. Therefore, PE fresh-keeping films should be selected when purchasing fresh-keeping films.
From the physical point of view, the fresh-keeping film has moderate oxygen permeability and moisture permeability, adjusts the oxygen and moisture content around the fresh-keeping products, blocks dust, and thus extends the fresh-keeping period of food. Therefore, it is necessary to choose different fresh-keeping films for different foods.
The fresh-keeping film on the market is generally divided into two categories: one is ordinary fresh-keeping film, which is suitable for keeping fresh in the refrigerator; One type is microwave oven fresh-keeping film, which can be used for both refrigerator and microwave oven. The latter kind of fresh-keeping film is far superior to the ordinary fresh-keeping film in heat resistance, non-toxic and other aspects. Therefore, consumers should pay special attention to the use of sub items.