Mutagenicity of nondialyzable melanoidins prepared from carbohydrates and L-tryptophan before and after nitrite treatment.

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Abstract
Nondialyzable melanoidins were isolated from the reaction mixtures of carbohydrates on their derivatives (such as sugars, an osone, and furfurals) with L-tryptophan in 0.1 M phosphate buffer (pH 7.0) after 4 wk at 37.degree. C or 1-2 h at 110.degree. C by dialyzing the mixtures against distilled water at 4.degree. C for 24 h. The melanoidins were tested for mutagenic activities toward Salmonella 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 200 .mu.g/late after nitrite treatment under acidic conditions. 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 400 .mu.g/plate after nitrite treatment. The mutagenic activities of the products were variable depending on the reacting conditions such as reaction time and reaction temperature. Nondialyzable substances from soy sauce and bean paste also showed weak mutagenic activities after nitrite treatment.