Migration of melamine from can coatings cross-linked with melamine-based resins, into food simulants and foods

Laurence Castle (1) , Emma Bradley (2) , Joanna Day (2) , Jennifer Leak (2)

1 FERA
2 Food Safety & Quality

Resins based on melamine-formaldehyde and related analogues such as methylolated melamine are used to cross-link coatings used inside food cans and on the metal closures of glass jars. Thirteen commercially coated cans and closures representing 80% of the European market, were tested using simulants under realistic industrial heat-processing conditions for canned and jarred foods. The food simulants and the retort conditions used were 3% acetic acid for 1 hr at 100ºC and 10% ethanol for 1 hr at 130ºC. The highest migration level seen for melamine into simulant was 332 µg/kg. There was no detectable migration of the melamine analogues cyanuric acid (<1 µg/kg) or ammelide (<5 µg/kg) from any sample. Twelve of the thirteen samples released no detectable ammeline (<5 µg/kg) but the coating giving the highest release of melamine did also release ammeline at 8 µg/kg with the higher of the two process temperatures used. Migration experiments into food simulant and foods themselves were then conducted using two experimental coatings made using amino-based cross-linking resins. Coated metal panels were exposed to the food simulant 10% (v/v) aqueous ethanol and to three foodstuffs under a range of time and temperature conditions both in the laboratory and in a commercial food canning facility using proprietary time and temperature conditions. The highest migration into a food was 152 µg/kg from the first coating processed for a long time at a moderate sterilisation temperature. The highest migration into simulant was also from this coating at 220 µg/kg when processed at 134oC for 60 mins, dropping to 190 µg/kg when processed at 123oC for 70 mins. Migration from the second coating was quite uniformly 2 to 3 times lower under all tests. These migration results were significantly higher than the levels of melamine extractable using 95% ethanol at room temperature. The experiments show that commercial canning and retorting can be mimicked in an acceptable way using laboratory tests with an autoclave or a simple pressure cooker. The results overall show there is hydrolytic degradation of the melamine-cross-linked resins to release additional melamine. There is a strong influence of the temperature of heat treatment applied with foods or simulants but only a minor influence of time of heating and only a minor influence, if any, of food/simulant acidity.

Mots clés: Life Sciences

Laurence Castle, Emma Bradley, Joanna Day, Jennifer Leak. Migration of melamine from can coatings cross-linked with melamine-based resins, into food simulants and foods. Food Additives and Contaminants, 2010, 28 (2), pp.243. ⟨10.1080/19440049.2010.536167⟩. ⟨hal-00654143⟩