In daily life, the close relationship between food packaging and food has long been recognized by thousands of households. Whether it is a store, a supermarket, or every family, beautifully designed, practical and convenient food packaging can be seen everywhere. It is hard to imagine what it will be like to deliver unpackaged food to every consumer.

In fact, food packaging is a process in the modern food industry, just like the personal clothing of food. It not only protects and promotes food, but also facilitates the storage, transportation and sale of food. To a large extent, food packaging has become an integral part of food, which will directly or indirectly affect food quality.

1 packaging materials

Residues of hazardous substances in food packaging mainly originate from packaging materials, especially inks and solvents that contain hazardous chemical materials such as benzene, n-hexane, and halogenated hydrocarbons as the main raw materials in the packaging and printing process. Moreover, such inks and solvents rich in harmful substances can also cause acute and chronic poisoning of operators during the production process, which not only affects the cooperative relationship between labor and management, but also seriously affects social stability.

Food packaging materials mainly include polyethylene, polypropylene, polyester, polyamide and other polymer materials. These packaging materials show great differences due to their own molecular structure, molding process and additives added. Therefore, it is particularly important for food manufacturers to choose a packaging material suitable for their products, otherwise food safety problems will arise. For example, due to the poor barrier properties of the material, the shelf life of liquid milk will be shortened or even deteriorate in a short period of time. As for the cling film, the freshness of vegetables cannot be guaranteed without proper ventilation. The potential harm of PVC cling film itself to the human body mainly comes from two aspects: one is that the residual amount of vinyl chloride monomer in the PVC cling film exceeds the standard, and the other is the use of DEHA plasticizer in the process of adding dicing to the PVC cling film, which is exposed to grease or heating. At times, DEHA is easily released, and it is harmful to health after entering the human body with food.

Bisphenol A is a chemical substance commonly used in plastic food packaging materials, and it is also used in tin can inner coatings and adhesives. Bisphenol A in plastic food packaging can be incorporated into food after heating, and it has an estrogen-like function. Not long ago, American researchers found through animal experiments that BPA may increase the risk of breast cancer in women.

2 Printing ink

In addition to the general bonding force and abrasion resistance of the food packaging film, the food packaging film must be able to withstand the requirements of boiling treatment, as well as freeze resistance, heat resistance, etc., to ensure that it is not in the process of transportation and storage. Phenomena such as ink shedding and condensation will occur.

Relevant Italian authorities found traces of photosensitive chemical substance-isopropyl thioxanthone in Nestle baby milk after sampling and testing. This substance originally exists in the printing ink of the baby milk packaging box, and it may be that a small amount of ink penetrates into the baby milk. There have also been incidents of printing ink contaminating food in China. In 2005, a food factory in Gansu found that the potato chips produced had a strong smell, and the factory immediately took back more than 600 boxes of products that had been wholesaled to the market. After testing by the Chemistry Laboratory of Lanzhou University, it is believed that the strange smell comes from the benzene in the printing ink of food packaging bags, and its content is about 3 times the allowable amount. If the residual amount of benzene exceeds the standard, it may cause cancer and blood system diseases.

At present, most inks contain benzene and can only be diluted with mixed solvents containing toluene. If the company uses low-purity cheap toluene when producing food packaging bags, the problem of benzene residues will be more serious. The problem is that although the relevant standards set a limit on the benzene content of food packaging materials, it is difficult for companies to control the limit. The reason is that the cost of benzene testing is quite high, and a package testing will cost more than 1,000 yuan.

3 printing accessories

Food packaging and printing pollution has become one of the main causes of secondary food pollution. Benzene, which has long been recognized as a carcinogen, is currently mainly used as a solvent for composite packaging material adhesives and plastic printing inks. Since benzene solvents are not completely volatilized during the printing process, it is possible that benzene substances may remain in the packaging materials. During the food packaging process, benzene penetrates into the food, causing food pollution.

According to statistics, in 2004, among the plastic inks for food and pharmaceutical packaging produced by large-scale manufacturers in my country, the content of chlorinated polypropylene ink used for BOPP film printing accounted for more than 60%, and the ink solvent and dilution solvent of this system Among them, the content of benzene solvents generally accounts for about 50%, which not only endangers human health, but also affects the healthy development of my country's food packaging industry and even the entire food industry. The benzene solvent remaining in the package is easily adsorbed by the food in the package, causing food contamination. Although the benzene-soluble ink can remove most of the toluene solvent by drying during printing, the pigment in the ink is still prone to residue due to the strong adsorption of the pigment.

In March 2006, at a symposium on the hygiene and safety of food plastic packaging materials held by the Plastic Packaging Committee of the China Packaging Federation, the participants agreed that the safety situation of food plastic packaging materials in my country is very severe, and many food plastic packaging materials on the market are difficult to Meet the requirements for food safety, hygiene and environmental protection. Benzene solvents are more toxic. If they penetrate into the skin or blood, they will endanger human blood cells and hematopoietic function, damage the human nervous system, and cause leukemia. The US FDA lists it as a carcinogenic chemical. Therefore, developed countries such as the United States, Western Europe, and Japan clearly stipulate that benzene-based solvents are prohibited in food packaging printing. On the contrary, my country has no clear regulations so far. In the production of food packaging films and bags, benzene (toluene, xylene) solvents are commonly used as solvents for inks and adhesives, and there is no management and supervision. At present, the relevant departments should be determined to strictly manage them.

4 printing process

Recently, food packaging bags in my country are basically gravure printing. All kinds of food packaging bags seen in supermarkets, including biscuits, pastries, milk powder, etc., are basically printed with chlorinated polypropylene inks. Mostly. While Europe and the United States mostly use flexo printing, flexo printing is slightly inferior to gravure in terms of dot performance, and the printing quality is slightly inferior, but it takes the lead in environmental protection. In our country, the acceptance of environmental protection technologies such as flexo printing in the market is not high. Because flexo printing uses the principle of embossing, it has fewer colored inks, thinner, and not very high coloring than gravure printing with heavy oil and color. In terms of brightness, it is not as bright as gravure.

In recent years, due to the excessively high residues of harmful substances in food packaging, foods have been contaminated and poisoned frequently, which has brought many unfavorable factors to the establishment of a harmonious society. In September 2004, the inspection results of food packaging (film) announced by the General Administration of Quality Supervision, Inspection and Quarantine showed that, in addition to general plastic bags, the unqualified rate of sampling for special food packaging bags was as high as 15%. In recent years, the sampling qualification rate of packaging bags in various places is generally low, and the qualification rate is only 50%-60%. Relevant parties must strengthen the research of ink, adhesive, printing, and composite processing new technologies and new processes as soon as possible to produce safe and environmentally friendly food packaging products