Coffee aroma quality: investigation of the reaction pathways involved in the degradation of thiols.

A mixture of volatile thiols covering a large range of physico-chemical properties was monitored over time in the presence of a coffee brew. The analysis was conducted by SPMEGC-MS. Additives inhibiting specific reaction pathways were preincubated with the brew prior to thiol addition. Degradation kinetics of the volatile thiols were characterised by their rate constants k(obs). The results suggest that thiols might disappear via two different major mechanisms depending on their structure. Aliphatic thiols like ethanethiol react by irreversible nucleophilic addition to matrix components generated by oxidation. Benzylic thiols like 2-furfurylthiol react partially following this same pathway but degrade also via radical cascade reactions.