As the Weather Turns Cold, Is Heating Plastic Packaging Harmful?

As the weather gradually turns cold, when buying breakfast you will notice vendors soaking plastic-packaged soy milk or milk in hot water, so that it is warm when we drink it; if the food or drink you buy is a little cold, some people also choose to put it in the microwave for a slight heating, but many plastic-packaged foods give off a faint plastic smell after heating. Are these the plasticizers or other additives of legend, and are they harmful to the human body?

In this regard, Professor Lu Yun of the School of Chemistry and Chemical Engineering at Nanjing University explained that plastic products generally used to hold food are polyethylene and polypropylene, and soaking them in water for heating should be safe. At the same time, many plastic products used for food also contain other additives, such as mold release agents and lubricants; at high temperatures, some additives with relatively active components may decompose, but this high temperature cannot be the temperature of hot water soaking, which is below 100℃.

In the past two years, new packaging on China's beverage market has gradually increased. At present, the main types of plastics used for beverage packaging are as follows:

1. PE (polyethylene):

PE is the synthetic resin with the largest output in the world and also the most consumed plastic packaging material. Polyethylene products are divided into three types: low density, medium density and high density. Among them, high-density polyethylene (HDPE), because of its higher crystallinity, has better hardness, airtightness, mechanical strength and chemical resistance, so it is widely used in blow molding to make bottles and other hollow containers. Taking advantage of PE's good heat seal performance, containers made of various composite materials can hold lemon juice, fruit juice and various other beverages.

1. PVC (polyvinyl chloride):

PVC can be roughly divided into three categories: rigid products, flexible products and paste products. PVC bottles produced by injection stretch blow molding have no seams and uniform wall thickness, and can hold carbonated beverages such as cola and soda; PVC bottles produced by extrusion blow molding are only suitable for holding fruit juice and mineral water.

1. PP (polypropylene):

The development of transparent polypropylene packaging bottles has been a hot spot in plastic packaging at home and abroad in recent years. With the successful development of a transparency modifier—nucleating agent—adding 0.1%–0.4% sorbitol dimethylbenzylidene (benzaldehyde) nucleating agent to ordinary PP, the resulting highly transparent PP bottles can be widely used in beverage packaging that requires thermal sterilization and high-temperature filling, such as concentrated fruit juice. With a suitable price and resistance to pressure and temperature, they are new rivals to PS, ABS, PET and PE bottles.

1. Polyester (PET or PETP):

PET bottles produced by the two-axis stretch blow molding method have good transparency and high surface gloss, presenting a glass-like appearance, and are the most suitable plastic bottles to replace glass bottles. In recent years, China's PET bottle production has developed rapidly, and they are widely used in various tea drinks, fruit juices and other beverages requiring hot filling, such as PepsiCo's 600ml, 1.25L, 2L and 2.5L PET bottles. Different capacities target the different needs of individuals and families, and are well received by consumers.

At present, most of the thin plastic bags used at breakfast stalls are transparent and low-priced, mostly processed from PVC (polyvinyl chloride) as raw material, and most are recycled materials. This kind of plastic bag containing polyvinyl chloride will release toxic substances such as lead when encountering high temperatures. When the temperature exceeds 50℃, the toxic components in the plastic bag will seep out, thereby contaminating the food and harming the human body. When the temperature reaches 80℃, it will melt in the heat and release toxic and harmful substances. Hot (cooked) food is above 40℃, while freshly fried dough sticks and freshly made soy milk are about 90℃.

In fact, in daily use, using contact plastic bags that meet standards can avoid these troubles, but the public should still try not to use plastic bags for high-temperature and oil-containing foods; overly hot food should also be left to cool before being bagged. Correct use in daily life will not cause harm to the body.