National Research Institute of Brewing, Higashihiroshima, Hiroshima 739-0046, Japan.
J Agric Food Chem. 2022 Oct 19;70(41):13413-13418. doi: 10.1021/acs.jafc.2c06099. Epub 2022 Oct 6.
Disulfide-bonded thiols in malt and hops were first identified as possible precursors of thiols in beer. The presence of disulfide-bonded 3-mercaptohexan-1-ol (3MH) was confirmed in malt and hops by observing an 8.9-9.9 times increase in the 3MH concentration in hopped water and unhopped wort after the reduction using tris(2-carboxyethyl)phosphine (TCEP), a reducing agent specific for disulfide bonds. The presence of disulfide-bonded 4-mercapto-4-methylpentan-2-one (4MMP) was confirmed in hops by observing 2.1 and 5.1 times increase in the 4MMP concentration after reduction in hopped water. Proteins, peptides, and amino acids having sulfhydryl groups or other thiol substances were assumed to form disulfide bonds with polyfunctional thiols in malt and hops. The release of thiols by the reduction of disulfide-bonded thiols during fermentation was first identified. A 65-82% of disulfide-bonded 3MH were reduced during fermentation, and as a result, concentrations of 3MH in hopped water and unhopped wort increased by 9.5-14.2 times during fermentation.
二硫键结合的硫醇在麦芽和啤酒花中首次被确定为啤酒中硫醇的可能前体。通过观察使用三(2-羧乙基)膦（TCEP）还原后，麦汁和水中小麦和啤酒花中二硫键结合的 3-巯基己烷-1-醇（3MH）的浓度增加了 8.9-9.9 倍，证实了其存在，TCEP 是一种专门针对二硫键的还原剂。通过观察到水中小麦和啤酒花中二硫键结合的 4-巯基-4-甲基戊-2-酮（4MMP）在还原后浓度增加了 2.1 和 5.1 倍，从而证实了 4MMP 的存在。具有巯基或其他硫醇物质的蛋白质、肽和氨基酸被认为与麦芽和啤酒花中的多官能硫醇形成二硫键。首次发现发酵过程中二硫键结合的硫醇还原释放硫醇。在发酵过程中二硫键结合的 3MH 中有 65-82%被还原，因此，在发酵过程中，水中小麦和麦汁中二硫键结合的 3MH 浓度增加了 9.5-14.2 倍。
