Corporate Research, Firmenich SA, routes des Jeunes 1, 1211 Geneva 8, Switzerland.
Food Chem. 2013 Nov 15;141(2):1078-86. doi: 10.1016/j.foodchem.2013.04.043. Epub 2013 Apr 24.
Cysteine-S-conjugates (CS-conjugates) occur in foods derived from plant sources like grape, passion fruit, onion, garlic, bell pepper and hops. During eating CS-conjugates are degraded into aroma-active thiols by β-lyases that originate from oral microflora. The present study provides evidence for the formation of the CS-conjugates S-furfuryl-l-cysteine (FFT-S-Cys) and S-(2-methyl-3-furyl)-l-cysteine (MFT-S-Cys) in the Maillard reaction of xylose with cysteine at 100°C for 2h. The CS-conjugates were isolated using cationic exchange and reversed-phase chromatography and identified by (1)H NMR, (13)C NMR and LC-MS(2). Spectra and LC retention times matched those of authentic standards. To the best of our knowledge, this is the first time that CS-conjugates are described as Maillard reaction products. Furfuryl alcohol (FFA) is proposed as an intermediate which undergoes a nucleophilic substitution with cysteine. Both FFT-S-Cys and MFT-S-Cys are odourless but produce strong aroma when tasted in aqueous solutions, supposedly induced by β -lyases from the oral microflora. The perceived aromas resemble those of the corresponding aroma-active thiols 2-furfurylthiol (FFT) and 2-methyl-3-furanthiol (MFT) which smell coffee-like and meaty, respectively.
半胱氨酸-S- 共轭物（CS 共轭物）存在于植物源食物中，如葡萄、百香果、洋葱、大蒜、甜椒和啤酒花。在食用过程中，CS 共轭物通过口腔微生物群中的 β-裂合酶降解为具有香气活性的硫醇。本研究提供了证据证明，在木糖与半胱氨酸于 100°C 下反应 2 小时的美拉德反应中形成 CS 共轭物 S-糠基-L-半胱氨酸（FFT-S-Cys）和 S-（2-甲基-3-呋喃基）-L-半胱氨酸（MFT-S-Cys）。CS 共轭物通过阳离子交换和反相色谱分离，并通过（1）H NMR、（13）C NMR 和 LC-MS（2）进行鉴定。光谱和 LC 保留时间与真实标准品相匹配。据我们所知，这是首次将 CS 共轭物描述为美拉德反应产物。糠醇（FFA）被提议为与半胱氨酸发生亲核取代的中间体。FFT-S-Cys 和 MFT-S-Cys 均无味，但在水溶液中品尝时会产生强烈的香气，据推测是由口腔微生物群中的β-裂合酶引起的。所感知的香气类似于相应的具有香气活性的硫醇 2-糠基硫醇（FFT）和 2-甲基-3-呋喃硫醇（MFT），它们分别具有咖啡味和肉味。
