In our daily life, plastic wrap is like the unknown hero, guarding our food safety and prolonging the shelf life of food. However, the "hero" has recently been embroiled in a controversy over health and safety.
Some people say that there are harmful things hidden in plastic wrap, and if you use too much, it is not only toxic, but also may cause cancer. Is this true, or is it a rumor with ulterior motives?
1. Scientific experiments on plastic wrap and bacterial reproduction
Researchers have done such an experiment: in the case of watermelon, they cut a watermelon into six pieces, three of which were put in the refrigerator so clean, and the other three pieces were carefully wrapped in plastic wrap.
As a result, four hours later, the number of bacteria in the watermelon without plastic wrap was 10, and the number of bacteria in the cling film was 65, and after seven hours, the number of bacteria in the two was 75 and 90 respectively, and by 20 hours, the difference between 80 and 210 was not a star and a half.
Doesn't this experiment illustrate the problem? Don't worry, it's really not that simple. Although the experiment showed that there were more bacteria in the watermelon covered with plastic wrap, this could not be blamed entirely on the plastic.
Bacteria have three treasures to multiply: a source of pollution, a suitable temperature, and a moist environment. Once the watermelon is cut, the source of pollution in the kitchen may follow the car, coupled with the airtight environment of plastic wrap and the temperature suitable for bacterial growth in the refrigerator, these three conditions hit it off, and the bacteria on the watermelon will naturally be happy to thrive.
2. Common plastic wrap materials and their safety
There are many types of plastic wrap on the market, but there are only a few common ones, such as polyethylene (PE), polyvinyl chloride (PVC) and polymethylpentene (PP). These names may sound scary, but you need to know that they are actually plastic materials that are commonly used in everyday life.
For example, PE, this thing is colorless and odorless, and the plastic wrap made of it has good air permeability and water permeability, but it is almost meaningless in heat resistance, so it can not be wrapped in high-temperature food.
As for PVC, this guy has good transparency and is often used to wrap those candies and medicines that make people salivate when they look at it, but it has a problem, it may release harmful plasticizers when it encounters high temperatures, which is not good for the body, and long-term exposure may indeed have a risk of causing cancer.
3. National standards and health indicators for plastic wrap
In China, the production and use of plastic wrap is regulated by strict national standards. According to national food safety standards, testing for specific migration levels in food contact materials and articles is essential.
For example, the GB 9685-2016 standard specifies the types of additives allowed to be used in food contact materials and products, their uses, and the amount used.
The use of plasticizers in PVC cling film is particularly stringent, as certain types of plasticizers, such as phthalates, have been shown to cause disruption to the human endocrine system, and long-term exposure has even been linked to certain types of cancer.
In addition, the hygienic standard GB 4806.7-2016 for polyethylene resin for food packaging clearly states that heavy metals and other harmful substances shall not be detected in polyethylene (PE) plastic wrap.
In addition, there are strict limits for migratory substances to ensure that even small amounts of migration during food contact do not pose a threat to human health.
In the actual supervision, the relevant departments will regularly conduct random inspections on the plastic wrap products sold in the market to ensure that all products can meet the national standards.
If consumers find that the plastic wrap has an abnormal smell or discoloration during use, it may be a sign of material degradation or substandard products, and should stop using it immediately and report it.
Fourth, how to distinguish different materials of plastic wrap
1. Sensitivity test: Generally, the plastic wrap made of PE material will be softer and more flexible in the feel, easier to stretch and tear, and the edge will be neater when torn;
PVC plastic wrap will feel harder and more elastic, and the edges may be more jagged after tearing. PVDC plastic wrap is somewhere in between, but due to its excellent air insulation, the thickness tends to be more uniform and the feel is different.
2. Combustion test: Although it is not recommended for consumers to do it themselves, theoretically, different materials of plastic wrap will exhibit different characteristics when burned. The color of the flame produced by PE plastic wrap when it is burned is yellow, and it will drip paraffin-like residue after burning, and it smells of candle smoke;
PVC plastic wrap may produce a green flame with a pungent chlorine smell and a hard and black burning residue when burned, while PVDC plastic wrap is more complex to burn, but it is usually difficult to continue burning and may release a pungent odor when burning.
3. Water test: Put the plastic wrap in the water, the PE plastic wrap will float on the water because the density is less than that of water (about 0.91-0.96g/cm³).
PVC and PVDC plastic wrap may sink or float in the middle layer due to its density usually greater than that of water (PVC is about 1.3-1.45 g/cm³). This property can be used as a simple identification method, but the actual effect will vary depending on the thickness and densification of the plastic wrap.
4. Transparency and gloss: Transparency and gloss are also a means of distinguishing the material of plastic wrap. Generally, PE plastic wrap has better transparency, but the degree is not as good as PVC.
PVC plastic wrap is excellent in terms of transparency and luster, and it looks "bright". PVDC cling film is characterized by better transparency and gloss even at higher thicknesses, as well as better freshness.
5. Tensile test By stretching the plastic wrap, you can feel the elasticity and strength of different materials. PE plastic wrap is easy to deform after stretching, and the tensile strength is relative to that of VC, but it is not easy to return to its original state after stretching.
PV recovers even if stretched. In terms of feel, it will be higher in terms of efficiency and oxygen insulation, and relatively thick materials are used for consumers, and it is very important to understand and distinguish between different materials of plastic wrap to choose the products that best meet their daily use needs.
5. The application and precautions of plastic wrap in daily life
In modern home kitchens, plastic wrap has become almost an indispensable item. It plays a vital role in prolonging the shelf life of food and avoiding cross-contamination of ingredients. However, improper selection and use can pose health risks.
From the perspective of scientific materials science, the safety of plastic wrap is of paramount importance. For example, polyethylene (PE) is widely considered to be the safest plastic wrap material and is suitable for food contact.
It is free of harmful substances and stable at low temperatures, making it ideal for refrigerated foods. However, PE cling film needs to be used with caution when using it in a high-temperature environment, as exceeding its temperature tolerance range may lead to the migration of chemicals into food.
Another important consideration when using plastic wrap is to avoid direct contact with foods that are high in fat and acid. Certain materials of plastic wrap may release harmful substances under these conditions.
Therefore, for high-temperature cooking and storage of such foods, it is wise to choose products that are designed for microwave ovens or hot food.
summary
Eco-friendly plastic wrap is becoming more and more important in today's society. With the increase of consumers' awareness of environmental protection and their concern for health, a variety of plastic wrap products made of recycled materials have emerged.
Future trends are likely to revolve around improving the functionality and economic viability of these products. With the advancement of technology and the expansion of production scale, it is expected that more environmentally friendly plastic wrap with competitive prices and better performance will be available on the market in the future.