1. Printing auxiliaries
Food packaging printing contamination has become one of the main causes of secondary food contamination. Benzene has long been recognised as a carcinogen and is currently used mainly as a solvent in adhesive and plastic printing inks for composite packaging materials. Due to the incomplete evaporation of phenyl solvents during the printing process, phenyl substances may remain in the packaging material. During the food packaging process, benzene substances penetrate into the food and thus contaminate it.
2. Printing inks
Food packaging film, in addition to the general bonding and abrasion resistance with the substrate, also requires the ink to withstand the requirements of sterilization and boiling treatment, as well as frost resistance, heat resistance, etc., to ensure that in the process of transportation and storage. No flaking or condensation of the ink will occur.
Italian authorities found traces of a photosensitive chemical, isopropylthioxypyrimidine, in Nestlé's infant formula after sampling and testing. This substance was originally present in the printing ink of the infant formula boxes and it is possible that trace amounts of the ink penetrated into the infant formula. Incidents of ink contamination of food have also occurred in China.
3. Printing process
China's food packaging bags are basically gravure printing. Supermarkets see a variety of food packaging bags, including biscuits, cakes, milk powder and other packaging, basically printed with chlorinated polypropylene ink. The majority of the. Most countries, such as Europe and the United States use flexographic printing. Flexographic printing is slightly inferior to gravure printing in terms of dot performance and slightly poorer print quality, but is at the forefront in terms of environmental protection. In China, environmentally friendly technologies such as flexographic printing are not yet well accepted in the market. As flexographic printing uses the principle of letterpress printing, it has less colouring ink, is thinner and not very colourful compared to gravure printing which is heavy on oil and colour. In terms of brightness, it is not as good as the brightness of gravure printing.
4. Packaging materials
The residues of harmful substances in food packaging mainly come from packaging materials, especially inks and solvents containing harmful chemicals such as benzene, n-hexane and halogenated hydrocarbons, with the packaging printing process as the main raw material. Moreover, such inks and solvents rich in harmful substances can also cause acute and chronic poisoning of operators in the production process, which not only affects the cooperative relationship between employers and employees, but also seriously affects social stability.