Comparative mutagenicity of nine brands of coffee to Salmonella typhimurium TA100, TA102, and TA104

Nine coffee preparations, four caffeinated instant brands, three caffeinated drip coffees, and two decaffeinated coffees, one of which was an instant brand, were evaluated for mutagenicity by the Ames assay using Salmonella typhimurium TA100, TA102, and TA104. All the coffees contained direct-acting mutagens, which reverted the three strains. The inclusion of a rat microsomal enzyme preparation reduced the mutagenic response of the three strains in the presence of some of the coffee samples. Both glyoxal and methylglyoxal, 1,2-dicarbonyls found in the coffees were mutagenic. The concentration of glyoxal, methyglyoxal, diacetyl, and guiacol were measured by gas chromatography/mass spectrometry. Caffeine, furfural, and 5-methylfurfural concentrations were determined by high performance liquid chromatography. Although lower concentrations of methyglyoxal were found in the drip caffeinated coffees, the mutagenic potency of these preparations was higher than the instant coffees on a weight basis especially when TA104 was the indicator organism. Our findings agree with those of other workers who have shown that carbonyl compounds, which were present in all the brands tested, are partially responsible for the mutagenic response of coffee but that additional mutagens are also present.