Food Labels: Which Tests Do Ink and Adhesive Need

When a food manufacturer audits a label supplier, the first document requested is usually a food grade certificate for the face stock. The two layers that actually cause trouble are the ink and the adhesive, because those are what migrate into the food or through a thin barrier toward it.

Direct contact or indirect contact first

Direct contact means the label faces the food, or the label is itself part of the packaging, such as a wrap applied straight to pastry or a sealing sticker. That situation falls under the full set of food contact material requirements. Indirect contact means the label sits on an outer carton or film, with plastic, board or glass in between, so the food never touches it. The requirements are lighter, but when the barrier is thin, storage is warm and time is long, migration still happens and cannot be ignored.

The standards that apply

In China the framework is the GB 4806 series, which is split by material: paper and board, plastics, rubber, coatings and so on. The general safety standard sets out the principles for migration, raw material requirements and marking. Additive use is checked against GB 9685. The actual limits, test conditions and pass criteria live in the text of each part, and they vary substantially with material and with the food simulant used, so the figures need to be read from the standard rather than recalled.

For export, the destination rules apply as well. The European Union has a framework regulation plus a specific measure for plastics in food contact, and the United States works through the relevant FDA provisions. Which one governs depends on the material and the application, and the official text decides.

Ink is the high risk layer

Conventional UV inks cure through photoinitiators, and photoinitiator residue migrating into food is one of the most discussed failure modes in the sector. Low migration inks work by switching to larger molecule photoinitiators that diffuse to the surface far less readily, and they demand higher curing energy. If curing is incomplete, residue goes up rather than down, so the cure needs verifying rather than assuming.

One direction gets overlooked: printing on the food side. Some labels are printed on both faces, and some roll labels carry instructions on the reverse. If that face touches food, the ink is a food contact material and has to be treated as one.

Adhesive by type

Water based acrylic, hot melt, solvent based and rubber based carry different migration profiles. Water based adhesives have low residual monomer and generally lower risk. Solvent based adhesives migrate if drying is incomplete. Rubber based adhesives bring antioxidants and tackifying resins, both small molecules worth asking about. Cold chain and removable formulations are more complex again, so they deserve an extra question during the audit.

Three documents to request

A declaration of compliance stating which standard the product meets, which food categories it suits and any conditions on contact. A test report showing the laboratory, the test items, the simulant and the migration conditions, with the product code matching what is actually being supplied. And a commitment to notify formulation changes, because switching ink or adhesive suppliers happens routinely, and an unreported change invalidates every report issued before it.

One task sits on your side. Write down the real conditions of use and hand them to the supplier: the food type, storage temperature, whether it is heated, and the expected contact time. A dry goods label at room temperature and a ready meal that goes into a microwave are not in the same category, and the requirement differs by an order of magnitude.