He said that the adhesive tape is based on the plastic film (plastic base tape), and the surface of one side is roughened by high-voltage corona, and then coated with adhesive (glue), and then cut into strips and divided into small rolls, commonly known as self-adhesive or pressure-sensitive adhesive.
Baseband and adhesive belong to polymer products. Pure polymer materials are difficult to be digested and absorbed by human body because of their large molecular weight, and it is also difficult to enter the blood circulation system of human body, so they can be regarded as non-toxic.
In order to verify whether the tape used to bind vegetables is toxic or not, Li Yulin specially went to the supermarket to take samples and made a preliminary dissolution and combustion experiment on the tape. After burning, the plastic base band of the adhesive tape has no yellow-green and pungent smell of PVC burning, which can be preliminarily judged as a commonly used polypropylene film material, and it can be regarded as harmless under the existing food safety standards.
The adhesive composition of adhesive tape is complicated, which can't be detected by general experiments. However, oily adhesives are widely used in the market, which contain toluene, formaldehyde and other components.
Teacher Li explained that the harmfulness of adhesive tape is not as serious as the public imagined. During the production, processing and storage of the adhesive, most of the solvents have volatilized and the additives have migrated, so the content of harmful components is still very small. Moreover, because the surface of vegetables and fruits is wet and difficult to stick, it is rare that the adhesive remains on the surface of vegetables and fruits after the tape is torn off.
He said: "Compared with pesticide residues in some vegetables, the toxicity of tape residues is almost negligible, and it will not have obvious impact on human body if it is not ingested in large quantities for a long time."
Experts say:
Tape is a polymer product,
Non-long-term and large intake will not pose a threat to human health
■ Text/Figure Our reporter Tam Peng
Intern Wang Yijin
People who often go to the supermarket to buy food will find that most vegetables in the supermarket are bundled with tape and sold. Recently, many citizens questioned the safety of this kind of tape for binding vegetables. They speculated that the glue on the tape might be industrial glue, which contains carcinogens such as formaldehyde and is toxic to human body.
So, is there a scientific basis for people's doubts? What material is the adhesive tape used to bind vegetables? Is it toxic or not? Therefore, the reporter invited Li Yulin, a teacher from the Department of Chemistry and Materials Science of Hengyang Teachers College, to give a professional explanation.
In some supermarkets in our city, vegetables such as green onions, cowpeas, leeks, celery, Chinese cabbage, etc. are mostly tied with green or blue tape for convenience of sale, and some of them are tied with tape when they are weighed, or price tags are directly attached to vegetables and fruits, even if they are not tied with tape before sale.
Ms. Liu told reporters: "Some vegetables bought from supermarkets are often tied with tape. After the tape is torn off, there are still sticky things sticking to the vegetables. I wonder if eating this kind of vegetables will be harmful to human health?"
Mr. Li, a citizen, is very worried: "The cost of edible glue is higher than that of industrial glue. In order to save costs, it is estimated that the glue on the tape is made of industrial glue." He is worried that industrial glue is toxic and residues on vegetables may cause cancer.
many citizens agree with the saying that "tape residue may cause cancer". Some people even take the vegetables tied with tape home and wash them repeatedly, or simply peel off the parts of the vegetables contacted with the tape.
The manager of the fresh-keeping department of a large supermarket in the city has also encountered some citizens' doubts about the safety of the adhesive tape. For this reason, she specially consulted the adhesive tape manufacturer, and the manufacturer replied: "The materials used to make the adhesive tape are environmentally friendly and harmless, and have no harm to the human body." She also told reporters: "It is a common practice in the supermarket industry to bind vegetables with tape, and food safety is a sensitive issue, and supermarkets also attach great importance to it."
Reporter's investigation:
It is a common practice in the supermarket industry to bind vegetables with tape
Expert's advice:
It is suggested that supermarkets use straw ropes instead of tape,
The public can identify "bad" tape by "seeing two smells and burning three times"
Li Yulin said that the current laws and regulations on food safety and packaging in China have no clear regulations on tape for binding vegetables. However, some cities in China have issued a "ban" prohibiting the use of tape to bundle vegetables. For example, in early 211, the Harbin Municipal Agriculture Committee issued a "Notice on Prohibiting the Direct Use of Tape to Bundle Vegetables", requiring local supermarkets to cancel the behavior of directly bundling vegetables with tape.
He suggested that the supermarkets in our city can use straw rope instead of adhesive tape, or use special adhesive tape for food without toxic ingredients; It is effective for citizens to repeatedly clean or even cut off and throw away the parts of fruits and vegetables that have been in contact with the tape before eating.
In addition, Li Yulin also taught you several simple methods to identify the toxicity of adhesive tapes, namely, "seeing, smelling and burning". At first glance, the more viscous the glue, the greater the possibility of using harmful organic solvents such as toluene; Second, smell the smell of adhesive tape. The stronger the pungent smell, the higher the content of organic solvents or some harmful additives may be. Three burning refers to lighting the adhesive tape with a lighter, observing the color of the flame and fanning the smoke by hand to smell the smell from the side. If it is a blue flame, the sample melts and drips, and the smell is similar to a candle, it may be a relatively safe and hygienic polyethylene material; If it is a yellow-green flame and has a pungent and pungent smell, it can basically be concluded that it is made of PVC. Polyvinyl chloride usually needs to add a lot of oil-soluble plasticizers and other harmful additives.