Formation of carcinogenic 4(5)-methylimidazole in caramel model systems: a role of sulphite.

Aqueous caramel model systems consisted the D-glucose/NH(3)/sulphite were heated at 100°C for 2 h and amounts of carcinogenic 4(5)-methylimidazole (4-MI) formed were determined. The amount formed ranged from 7.0 to 155.0 ppm. A system with 0.1 M sulphite yielded the greatest amount of 4-MI, which was 54% more than that yielded from a system without sulphite. When the amount of sulphite increased over 0.1 M, the amount of 4-MI reduced. The greatest reduction was achieved with 0.2 M sulphite by 68% compared to 0 M sulphite, suggesting that sulphite plays an important role in the formation of carcinogenic 4-MI in caramel colour. Also, a system with 0.1 M sulphite yielded the most intense caramel colour but the other levels of sulphite did not change the colour intensity significantly. Sulphite contributed slightly to the level of flavour chemicals evaluated using pyrazine formation. The results suggest that sulphite addition at appropriate amount reduces 4-MI formation in caramel colour without sacrificing flavour and colour formation.