Studies on the mutagenicity of commercial preparations of the food colour Red 2G after purification or oxidation.

The UK-permitted, monoazo food colour Red 2G (C.I. 18050) has previously been shown to induce transition mutations in bacteria when tested with metabolic activation. Whilst this result has now been confirmed, later commercial food-grade batches of the dye have also been found to exhibit dose-dependent direct activity in fluctuation tests with E. coli WP2 uvr A. HPLC analyses revealed the presence of contaminants several of which were either eliminated or reduced in amount after laboratory recrystallization. A concomitant loss of mutagenicity occurred which was gradually regained with storage of purified preparations. Since peroxidation of standard samples significantly potentiated activity over a number of doses it is concluded that commercial mixtures contain at least one mutagenic impurity which may arise by spontaneous oxidation. The data are discussed in relation to the effects of oxidation on other aromatic amines and with respect to the use of this colour in foods.