Contribution of coffee aroma constituents to the mutagenicity of coffee.

About 40 coffee aroma constituents belonging to the classes of dicarbonyls, sulphur-containing compounds, furfuryls, N-heterocyclics and others were systematically evaluated in three Ames tester strains. Only aliphatic dicarbonyl compounds showed notable direct mutagenic activity, which mainly affected 'base-pair substitution' in Ames tester strains TA100 and TA102. Very weak effects were also seen with some N-heterocyclics, mainly affecting frameshift tester strain TA98 upon metabolic activation. However, it was shown that these N-heterocyclics do not contribute substantially to the mutagenicity in coffee. The hydrogen peroxide and methylglyoxal contents of coffee were determined up to 26 hr after preparation. Their concentrations tended to decrease whereas mutagenic activity decreased significantly with time in tester strains TA100 and TA102. It is concluded that several highly labile coffee constituents contribute to the bacterial mutagenicity and also that the synergism between hydrogen peroxide and methylglyoxal is not the main factor. The absence of coffee mutagenicity/carcinogenicity in rodents with these highly reactive coffee aroma compounds can be explained in part by detoxification of microsomal enzyme systems.