In daily life, the close relationship between food packaging and food has long been recognized by thousands of households. Whether in stores, supermarkets, or in every home, beautifully designed, practical and convenient food packaging can be seen everywhere. It's hard to imagine what it would be like if food without packaging was delivered to every consumer.
In fact, food packaging is just like the underwear of food, it is the last process of the modern food industry. It not only plays the role of protecting and promoting food, but also facilitates the storage, transportation and sales of food. To a large extent, food packaging has become an integral part of food and will have a direct or indirect impact on food quality.
1. Packaging materials
Residues of harmful substances in food packaging mainly come from packaging materials, especially inks and solvents containing harmful chemical materials such as benzene, n-hexane, and halogenated hydrocarbons as the main raw materials during 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 polymer materials such as polyethylene, polypropylene, polyester, and polyamide. These packaging materials show great differences due to their different molecular structures, molding processes and added additives. Therefore, it is particularly important for food manufacturers to choose a packaging material suitable for their products, otherwise food safety problems will occur. For example, due to poor barrier properties of the material, the shelf life of liquid milk will be shortened or even cause deterioration in a short period of time. For plastic wrap, if there is no appropriate amount of air permeability, the freshness of vegetables cannot be guaranteed. The potential harm of PVC cling film itself to the human body mainly comes from two aspects: first, the residual amount of vinyl chloride monomer in the PVC cling film exceeds the standard; second, the DEHA plasticizer is used in the adding process of PVC cling film, which is exposed to grease or heat. When consumed, DEHA is easily released and is harmful to health after entering the human body with food.
Bisphenol A is a chemical commonly used in plastic food packaging materials, as well as in tin can interior 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 discovered through animal experiments that bisphenol A may increase the risk of breast cancer in women.
2. Printing ink
In addition to the general bonding strength with the substrate and wear resistance, food packaging films also require ink resistance to sterilization and boiling treatment requirements, as well as freezing resistance and heat resistance to ensure that they can be used during transportation and storage. Ink will not fall off or condense.
Relevant Italian authorities found trace amounts of the photosensitive chemical substance isopropylthiaxantrone in Nestlé infant milk after sampling and testing. This substance originally existed in the printing ink of the baby milk packaging box, and it may be that a trace amount of the ink penetrated into the baby milk. There have also been incidents in China of printing ink contaminating food. In 2005, a food factory in Gansu discovered that the potato chips it produced had a strong, strange smell. The factory immediately recalled all the more than 600 boxes of products that had been wholesaled to the market. After testing by the Chemistry Laboratory of Lanzhou University, it was believed that the strange smell came from benzene in the printing ink of food packaging bags, and its content was about three times the national allowable amount. If the residual amount of benzene exceeds the standard, it may cause cancer and blood system diseases.
At present, most inks themselves contain benzene and can only be diluted with mixed solvents containing toluene. If companies use cheap toluene with lower purity when producing food packaging bags, the problem of benzene residue will be more serious. The problem is that although relevant standards set limits on the benzene content of food packaging materials, it is difficult for companies to achieve limit control. The reason is that the cost of benzene testing is quite high, with a package testing costing 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. Due to incomplete evaporation of benzene solvents during the printing process, benzene substances may remain in packaging materials. During the food packaging process, benzene substances penetrate into the food, causing food contamination.
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 inks used for BOPP film printing accounted for more than 60%, and the ink solvents and diluting solvents of this system The content of benzene solvents generally accounts for about 50%, which not only harms 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 packaging is easily adsorbed by the food in the packaging, causing food contamination. Although most of the toluene solvent can be removed by drying the benzene-soluble ink during printing, due to the strong adsorption of pigments in the ink, residues are still easy to occur.
In March 2006, at a symposium on health and safety of food plastic packaging materials held by the Plastic Packaging Committee of the China Packaging Federation, participating representatives agreed that the safety situation of food plastic packaging materials in my country is very serious, and many food plastic packaging materials on the market are difficult to Comply with national requirements for food safety, hygiene and environmental protection. Benzene solvents are highly 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, in developed countries such as the United States, Western Europe and Japan, it is expressly prohibited to use benzene solvents in food packaging and printing. On the contrary, our country has no clear regulations so far. In the production of food packaging films and bag making, benzene (toluene, xylene) solvents are commonly used as solvents for inks and adhesives. There is no management and supervision. It has reached a point where relevant departments should make up their minds to strictly manage this.
4. Printing process
The current food packaging bags in our country are basically gravure printed. Various food packaging bags seen in supermarkets, including biscuits, pastries, milk powder and other packaging, are basically printed with chlorinated polypropylene inks. Most of them. Most countries in Europe and the United States use flexo printing. Flexo printing is slightly inferior to gravure printing in terms of dot performance and printing quality, but it takes the lead in environmental protection. In our country, environmentally friendly technologies such as flexo printing are not highly accepted in the market. Because flexo printing uses the embossed printing principle, compared with gravure printing with heavy oils and heavy colors, the coloring ink is less, thinner, and the coloring degree is not very high. In terms of brightness, it is not as bright as gravure printing.
In recent years, due to high levels of harmful substances remaining in food packaging, food contamination and poisoning have occurred frequently, which has brought many unfavorable factors to the creation of a harmonious society. In September 2004, the General Administration of Quality Supervision, Inspection and Quarantine announced the results of random inspections of food packaging (film), which showed that, in addition to general plastic bags, the failure rate of special food packaging bags was as high as 15%. In recent years, the sampling pass rate of packaging bags in various places has generally been low, with a pass rate of only 50%-60%. Relevant parties must strengthen research on new technologies and processes for inks, adhesives, printing, and composite processing as soon as possible to produce safe and environmentally friendly food packaging products.