Requirements for the manufacture and use of food packaging inks in Germany

European countries have strict requirements on food packaging, but there are currently no specific regulations for printing inks used in food packaging. For this reason, ink manufacturers are obliged to comply with the requirements of the "method for manufacturing food packaging inks." This article describes the current requirements for the manufacture and use of food packaging inks in Germany.

Last year in Germany, there were trace amounts of isopropyl thioxanthone (ITX) in different beverages. This residue involves the use of photoinitiators in UV curable inks. When the printed product is wound, a small amount of ITX is transferred to the unprinted back surface by ink sticking, and the package is also made into the food as it is produced and packed. This situation has caused great concern in the community for the public, policy and authorities.

In the framework rule of European Community No. 1935/2004, regulations concerning materials and substances that come into contact with food are stipulated. These materials and substances, whether printed or non-printed, do not allow the following harmful ingredients to be transferred to food: endangering human health, Causes harmful changes in food ingredients, resulting in the effect of food quality on sensory organs.

Legal basis

So far there is no specific legislation on the limits of printing inks, permitted or prohibited inclusions and assessment methods. This situation has prompted people to try to borrow specifications from similar areas of technology. In addition, manufacturers joining the European Printing Ink Association have already been bound by the "Method Requirements for Food Packaging Printing Ink Manufacturing." The most important basis for evaluating the ink composition is "2002/72 specifications (for plastics and articles in contact with food)". It not only stipulates the total migration limit, but also specifies the maximum permissible residuals for the individual materials in the migration limit and daily necessities. Based on this, the materials listed in the plastic specification and used in the ink were evaluated. Of course, most ink materials are not included in this plastic specification. In order to protect the interests of consumers, a unified production method is stipulated by printing ink manufacturers. It specifies the choice of raw materials, their purity requirements and their effect on the sensory properties (odor and taste) as well as the consideration of the packaging structure and the influence of the printing process.

Ink composition

Here's how printing ink ingredients must meet the requirements of food packaging. Sheetfed offset is the most flexible printing method for different paper, paper size, paper weight, print design method, surface finishing and post-press processing. The drying mechanism of sheetfed offset inks is still characterized by thin oil penetration and oxidative drying of vegetable oils. However, the flexibility of a sheetfed offset and the use of a lower cost printer must be traded off at the expense of a few hours of oxidative drying time.

Tasteless

Considering the requirements of food packaging, the drying mechanism of sheet-fed offset printing ink has some defects. When the vegetable oil is oxidatively crosslinked, the thin oil becomes a three-dimensionally cross-linked solid. In addition to the desired polymerization, low molecular volatile fission products are produced which emit a special odor (after the ink has dried). This fission product will be transferred to the food and change the taste of the food. If non-barrier packaging is used for sensitive foods, the mechanism of ink oxidation drying must be abandoned. This means that the print's mechanical strength and abrasion resistance are inferior to those of commonly used offset inks.

Therefore, when using a non-oxidatively dried offset printing odorless ink, it is best to cover the surface with an odorless water-based coating. The odorless rating of prints is mostly based on the sensory center test (Robinson test according to DIN 10955) or on fission products (measurement of acetaldehyde content).

Hazard of migration

Due to the absence of a barrier layer in the packaging structure, there is a risk that the ink contents will be transferred to the food through the substrate, thus requiring the use of migration-free ink. None of the inks contained any less than 1,000 molecular weight inclusions.

This low-molecular material is particularly prone to spread through the substrate due to molecular motion.

In order to make the ink permeate, the molecular weight of the thin oil used therein is usually less than 1000, so the non-migrating ink does not contain a low molecular weight thin oil, but it penetrates slowly. To this end, it is necessary to take some measures, such as increasing the dusting, printing a small amount of deposits and the use of water-based varnish to cover the surface. In order to check the migration state of the ink substance, the printed matter was tightened in a detection transfer tank. Contact the unprinted side with a food simulant. After a predetermined time and temperature have been set, the chemical analysis shows which of the ink's contents pass through the printed matter and the amount of transmission.

Recently, Flint Ink Group launched odorless and migration-free sheetfed offset printing inks for food and cigarette packaging printing. Because there are many influencing factors, making food packaging is a very complicated process. From a purely legal point of view, the manufacturer of the final product is responsible for cooperating with all participants, specifying all requirements and steps in the production process. If necessary, carry out a migration test or check the effect on the senses. Only in this way can food packaging meet technical and legal requirements.