α-Mercaptoketone Formation during the Maillard Reaction of Cysteine and [1-13C]Ribose

The volatiles formed from [1-13C]-ribose and cysteine during 4 h at 95 °C in aqueous phosphate buffer (pH 5) were analyzed by headspace SPME in combination with GC-MS. The extent and position of the labeling were determined using MS data. The identified volatiles comprised sulfur compounds such as 2-[13C]methyl-3-furanthiol, 2-[13CH2]furfurylthiol, [1-13C]-3-mercaptopentan-2-one, [1-13C]-3-mercaptobutan-2-one, [4-13C]-3-mercaptobutan-2-one, and 3-mercaptobutan-2-one. The results confirm furan-2-carbaldehyde as an intermediate of 2-furfurylthiol, as well as 1,4-dideoxypento-2,3-diulose as an intermediate of 2-methyl-3-furanthiol and 3-mercaptopentan-2-one. Loss of the C-1 and C-5 carbon moieties during the formation of 3-mercaptobutan-2-one suggests two different mechanisms leading to the key intermediate butane-2,3-dione. Keywords: Maillard reaction; 2-methyl-3-furanthiol; 2-furfurylthiol; 3-mercaptopentan-2-one; 3-mercaptobutan-2-one; [1-13C]ribose; cysteine; 1,4-dideoxypento-2,3-diulose; solid-phase microextraction; Amadori compound; mass spectrometry