Fresh-keeping bags are generally made of three materials: polyethylene (PE), polyvinyl chloride (PVC), and polyvinylidene chloride (PVDC). Among them, PE, PVDC storage bags are relatively safe, PE is mainly used for the packaging of fruits and vegetables, PVDC is mainly used for the packaging of some cooked food and ham. Although PVC insurance bags are widely used in the packaging of food and vegetables, they have certain potential harm to the human body. Therefore, PVC storage bags are prohibited from being used for foods such as meat, cooked food, and tofu that can be eaten directly.

The raw materials of plastic bags are generally high-density polyethylene and low-density polyethylene. The former is the shopping bag of the supermarket, which is very hard to touch. The latter is mostly used for packaging foods and is soft to the touch. Dark plastic bags such as red, black and blue are mostly reprocessed from recycled plastic products. It is strictly forbidden to directly load food.

In summary, because of the special process of cling film, it has good gas permeability and fresh-keeping properties. The use of ordinary plastic bags for a long time will make the food deteriorate, and the material is not as safe as the storage bag. Therefore, the storage bag is more suitable for direct food.