When buying a fresh-keeping box or film, you must pay attention to whether it is marked with a specific name or chemical structure. If the product has only an English name but no Chinese logo, you should buy it with caution. At the same time, we must choose products marked with "food".
The fresh-keeping boxes are mainly made of polyethylene (PE) and polypropylene (PP). The price difference between the two products is not large, but polypropylene (PP) can better prevent the penetration of oil.
When buying fresh-keeping film, it is recommended to buy self-adhesive fresh-keeping film made of polyethylene (PE) first, especially when fresh-keeping meat and fruits, because from the perspective of safety, PE fresh-keeping film is the safest. If you want to keep fresh for a long time, it is recommended to choose polyvinylidene chloride (PVDC), because this material has better moisture retention performance, and the preservation period is the longest among the three materials. Polyvinyl chloride (PVC) fresh-keeping film has become the choice of many people because of its good transparency, good viscosity, good elasticity and low price. However, it must be noted that it can not be used for the fresh-keeping of greasy food, because it is a resin composed of polyvinyl chloride resin, plasticizer and antioxidant, and is not toxic. However, the added plasticizers, antioxidants and other main auxiliary materials are toxic. The plasticizers in daily-use PVC plastics mainly use dibutyl terephthalate and dioctyl phthalate. These chemicals are toxic. Moreover, the oil in food can easily dissolve the plasticizer "ethylammonia" in the fresh-keeping film, which has a great destructive effect on the human endocrine system and will disturb the hormone metabolism of the human body. Lead stearate, an antioxidant of polyvinyl chloride, is also toxic. Polyvinyl chloride (PVC) products containing lead salt antioxidant will precipitate lead when contacting with ethanol, ether and other solvents. When polyvinyl chloride containing lead salt is used as food packaging and meets with fried dough sticks, fried cakes, fried fish, cooked meat products, cakes and snacks, lead molecules will diffuse into the oil. Therefore, polyvinyl chloride plastic bags cannot be used to contain food containing oil. In addition, it is not allowed to use microwave oven for heating and high temperature use. Because PVC plastic products will slowly decompose hydrogen chloride gas at high temperature, such as about 50 ℃, which is harmful to human body, PVC products are not suitable for food packaging.