1. Packaging materials
The residual harmful substances in food packaging mainly come from packaging materials, especially from the use of harmful chemical materials such as benzene, n-hexane, halogenated hydrocarbons as the main raw materials in the packaging printing process, such as inks and solvents. Moreover, such inks and solvents rich in harmful substances can 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 flexible packaging materials mainly include polymer materials such as polyethylene, polypropylene, polyester, polyamide, etc. These packaging materials exhibit significant differences due to their molecular structure, molding process, and different additives added. Therefore, it is particularly important for food manufacturers to choose a packaging material that is suitable for their products, otherwise food safety issues may arise. For example, due to poor barrier properties of materials, the shelf life of liquid milk may be shortened or even cause spoilage in a short period of time. For plastic wrap, without an appropriate amount of air permeability, it is impossible to ensure the freshness of vegetables. The potential harm of PVC cling film to human health mainly comes from two aspects: firstly, the residual amount of vinyl chloride monomer in PVC cling film exceeds the standard, and secondly, the use of DEHA plasticizer during the addition process of PVC cling film can easily release DEHA when it comes into contact with oil or heating, which is harmful to health when food enters the human body.
Bisphenol A is a chemical substance commonly used in plastic food packaging materials, and is also used in tin can coatings and adhesives. Bisphenol A in plastic food packaging can be integrated into food after heating, and it has estrogenic properties. Not long ago, American researchers found through animal experiments that bisphenol A may increase the risk of women suffering from breast cancer.
2. Printing ink
The requirements for ink in food packaging films include not only general adhesion to the substrate and wear resistance, but also resistance to sterilization and boiling treatment, as well as frost resistance, heat resistance, etc., to ensure that ink does not fall off or condense during transportation and storage.
After sampling and testing, Italian authorities found trace amounts of photosensitive chemical substance - isopropylthioanthrone - in Nestle infant milk. This substance originally existed in the printing ink of baby milk packaging boxes, and may have been a trace amount of ink penetrating into baby milk. There have also been incidents of printing ink contaminating food in China. In 2005, a food factory in Gansu discovered a strong and peculiar smell in the production of potato chips. The factory immediately took back more than 600 boxes of products that had already been wholesale to the market. After testing by the Chemistry Laboratory of Lanzhou University, it is believed that the strange odor comes from benzene in the printing ink of food packaging bags, which is about three times the amount allowed by the country. If the residual amount of benzene exceeds the standard, it may cause cancer and blood system diseases.
3. Printing process
At present, food packaging bags are mainly gravure printed. Various types of food packaging bags seen in supermarkets, including biscuits, pastries, milk powder, etc., are mostly printed with chlorinated polypropylene ink. However, most countries such as Europe and America adopt flexographic printing as the main method. Flexographic printing performs slightly worse than gravure printing in terms of dot performance and printing quality, but it takes the lead in environmental protection.
