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Evidence of Enzymatic and Chemical Interconversions of Barley Malt 3‑Sulfanylhexanol Conjugates during Mashing

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posted on 2023-08-23, 16:05 authored by Cécile Chenot, Sonia Collin, Lucas Suc, Aurélie Roland
Recent studies have highlighted in malt the occurrence of the glutathionylated precursor of 3-sulfanylhexanol (G-3SHol) at concentrations reaching hundreds of μg/kg. Here, SIDA-LC-MS/MS was used to investigate the potential conversion of G-3SHol to its dipeptide and cysteinyl analogues during mashing. At 45 and 55 °C, malt γGT and carboxypeptidase activities quickly degrade G-3SHol (up to 90% loss), first to the cysteinylglycine conjugate and then to the cysteine conjugate (up to 205% increase). No γ-glutamylcysteine S-conjugate formation is observed. At 80 °C, despite enzyme inactivation, the G-3SHol level decreases steadily because of suspected imine formation with wort aldehydes at pH 5.5. More surprisingly, CysGly-3SHol is still generated at 80 °C. This indicates the presence in the wort of as yet unidentified precursors.

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