Chemistry and genotoxicity of caramelized sucrose.
Caramelization of a 1% sucrose solution at 180 degrees C accompanied characteristic changes in pH, Mr, UV-absorbance, and fluorescence values as well as increased reducing power activity after 40-60 min. Similar changes occurred to sucrose heated at 150 degrees C, after 150-240 min. Bioactivity of caramelized sucrose samples was tested for mutagenic activity, using Salmonella typhimurium strains TA-98 and TA-100, respectively, as well as the Saccharomyces D7 yeast strain for mitotic recombination and Chinese hamster ovary cells (CHO) to assess clastogenicity. Caramelized sucrose expressed no mutagenicity in the TA-98 strain, but gave positive (p < 0.05) results with the TA-100, base-pair substitution strain. Similarly, mitotic recombination in the Saccharomyces D7 yeast strain and clastogenic activity in CHO cells were induced when exposed to caramelized sucrose. In the all cases, preincubation with S-9 reduced (p < 0.05) the mutagenic activities of caramelized sucrose. Fractionation of the caramelized sucrose into volatile and nonvolatile compounds was performed and tested for clastogenicity using CHO cells. Volatile components contributed approximately 10% to total clastogenicity, which was enhanced by the presence of S-9. Nonvolatile components recovered, consisting of relatively lower Mr, gave highest (p < 0.05) clastogenic activity, denoting that higher Mr caramel colors are relatively free of this property.