Influence of water activity and reaction temperature of ribose-lysine and glucose-lysine Maillard systems on mutagenicity, absorbance and content of furfurals.

The effect of water activity (aw 0.98, 0.84 and 0.60) and reaction temperature (100, 120, 140 and 160 degrees C) on the mutagenic activity of the Maillard reaction products in heated ribose-lysine and glucose-lysine model systems, was investigated. In the ribose-lysine system, heated at 100 degrees C, the mutagenic activity of the mixture increased as the water activity was lowered. On the contrary, no dependence between mutagenic activity and water activity was observed in the glucose-lysine system. At higher temperatures, in both systems, the presence in the browned mixtures of an antibacterial activity interfering with the bacterial mutagenicity assay was observed. Under all the conditions tested, the ribose-lysine system turned out to be the most reactive by producing higher levels of mutagens. Furthermore, in this system, the antimicrobial interference was more easily detectable. In the model systems used, the browning reaction mixtures were analysed for their absorption spectrum between 200-460 nm, and for the accumulation of furfurals. The results obtained showed that, at temperatures between 120 and 140 degrees C there is a correlation among reaction temperature, absorbance at 420 and around 280 nm, mutagenic activity of the mixture and the level of furfurals. Changes in the levels of furfurals can be related to changes in mutagenicity of the browned mixtures.