Model Studies on the Oxidative Stability of Odor-Active Thiols Occurring in Food Flavors

Dilute ethereal solutions of mercaptoacetone (MA), 2-mercapto-3-butanone (MB), 3-mercapto-2-pentanone (MP), 2-methyl-3-furanthiol (MFT), and 2-furfurylthiol (FFT), either alone or in pairs, were stored at 6 °C. During a period of 10 days the oxidation of the thiols to the corresponding disulfides or mixed disulfides was followed by high-resolution gas chroraatography/mass spectrometry. In diethyl ether MFT showed the highest oxidation rate, which decreased in the order MFT ≫ MA > MB = MP = FFT. After 1 day, mixed disulfides (e.g. MFT-FFT, FFT-MB) were detectable when pairs of the five thiols dissolved in diethyl ether were stored at 6 °C. MFT oxidized more slowly in dichloromethane than in diethyl ether, and it was stable in pentane. However, a heat treatment increased the oxidation rate of MFT dissolved in dichloromethane or pentane.