Bound and Free 3-Sulfanylhexan-1-ol in Beer: Transfer and Release Rates from Kettle, Late, and Dry Hopping

The polyfunctional thiol 3-sulfanylhexan-1-ol (3SH) is a potent beer aroma compound, contributing fruity and tropical notes despite trace concentrations. Most 3SH occurs as bound S-conjugates in hops, which yeast can enzymatically cleave during fermentation. This study tracked 3SH and its S-conjugates under two hopping regimes (kettle and dry hopping) using Saccharomyces cerevisiae and S. pastorianus. Kettle hopping efficiently transferred hop-derived S-conjugates (∼90%) into wort, while yeast metabolism determined their fate: lager yeast extensively catabolized CysGly- and G-conjugates, yielding more 3SH, whereas ale yeast converted some G-conjugates into γGluCys-conjugates and left substantial G-conjugates unutilized when nondry-hopped. Dry-hopping approximately doubled both the precursor and the 3SH concentration, suggesting that yeast maintained a similar proportional conversion under both hopping regimes. However, less than 1% of total precursors was ultimately transformed into 3SH, and around half remained unused in the final beers. These findings clarify how yeast metabolism and hopping strategy interact to shape 3SH-derived beer aroma.