Unusual Profile of Thiol Precursors in Special Malts: First Evidence of Chemical Glutathione-/γGluCys- and CysGly-/Cys- Conversions

Polyfunctional thiols (PFTs) present in beers or wines are known to be released by yeast, during fermentation, from bound forms originally found raw materials. In the brewing field, huge amounts of S-conjugates have been evidenced several dual-purpose hop varieties. Malt, however, being major material beer, could also a significant contributor PFTs beer (cysteinylated, Cys- and glutathionylated, G- precursors 3SHol already identified few samples barley malt). Forty-two malts 2 1500 EBC five other malted cereals were screened characterize their thiol precursor profile (G- as well dipeptidic CysGly- γGluCys- 3SHol). First, it was confirmed that G-3SHol ubiquitous reaching up 320 µg/kg some samples, whereas Cys-3SHol remained at trace level 13 µg/ kg. Moreover, for first time, malt (up 10 11 CysGly-3SHol γGluCys-3SHol, respectively). pale malts, form shown proportional (in situ γGT malting process). This appeared no longer true special (ranging 5 45°EBC), whose correlated instead with (suspected chemical conversion dipeptide conjugate). As only (indicating another break Cys-Gly bond, here on G-3SHol) rye, spelt, wheat. No roasted malt.