Abstract
Nondialyzable melanoidins were isolated from the reaction mixtures of carbohydrates or their derivatives (such as sugars, an osone, and furfurals) with L-tryptophan in 0.1 M phosphate buffer (pH 7.0) after 4 weeks at 37°C or 1-2h at 110°C by dialyzing the mixtures against distilled water at 4°C for 24h. The melanoidins were tested for mutagenic activities toward S. typhimurium TA100 with and without nitrite treatment. None of these melanoidins was mutagenic without nitrite treatment, though the melanoidins from 3-deoxy-D-glucosone, furfural, 5-hydroxymethylfurfural, diacetyl and triose reductone were strongly mutagenic at the dose of 200μg per plate after nitrite treatment under acidic conditions. However, the melanoidins from D-xylose, D-arabinose, D-glucose, D-fructose, maltose, lactose and sucrose induced less than twice as many his+ revertant colonies as the negative control at the dose of 400μg per plate after nitrite treatment. The mutagenic activities of the products were variable depending on the reaction conditions such as reaction time and reaction temperature. Nondialyzable substances from soy sauce and bean paste also showed weak mutagenic activities after nitrite treatment.
