Ability of the Mandarina Bavaria hop variety to release free odorant polyfunctional thiols in late‐hopped beers

Abstract

The cysteinylated and glutathionylated precursors of 3‐sulfanylpentanol (Cys‐3SPol up to 197 μg/kg, G‐3SPol up to 14 mg/kg), recently reported in hops, were quantitated for the first time in the Mandarina Bavaria variety, along with the ubiquitous cysteinylated and glutathionylated forms of 3‐sulfanylhexanol (Cys‐3SHol up to 897 μg/kg, G‐3SHol up to 46 mg/kg). In contrast to findings with another new German cultivar, Polaris, no trace of 3‐sulfanyl‐4‐methylpentanol adducts (Cys‐ and G‐ 3S4MPol) was found. To assess the transfer rate of thiols from hops to finished beer, the same pilot Mandarina Bavaria hopped wort was fermented with two different dry yeasts, bottle refermented or not, and analysed. The data were compared with results obtained for a similarly produced commercial beer. In conclusion, despite significant variation between harvest years, Mandarina Bavaria appears not to contain outstanding amounts of free thiols or thiol S‐conjugates. Its S‐conjugate pool is sufficient, however, to bring 3SHol above its odour threshold. This work also suggests that since 3S4MPol was found near or above its threshold in most late‐hopped beers it does not originate from hops and that malt may be its main contributor. © 2021 The Institute of Brewing & Distilling

First evidence of the glutathione S ‐conjugate of 3‐sulfanylheptanol in green malt: discrepancy with the ubiquitous 5‐ and 6‐C analogues

“… na: not analysed; nd: not detected; d, detected at trace level (< 0.02 mg/kg in malts and hops, < 0.01 mg/kg in grapes). The shaded data were taken from already published results ( 16,18,21,29 ) . *value for Cys‐3SHol+Cys‐3S4MPol together.…”

“…S‐Benzyl‐L‐cysteine was used as the internal standard (IST) at 4‐8 mg/kg according to the sample. For solid samples, the extraction method was identical to that reported by Chenot et al ( 29 ) starting from either 150 mg milled malt or 100 mg milled hop pellets (solid/liquid extraction with acidified hydro‐alcoholic solution; centrifugation; loading of the supernatant on cation exchange resin; elution with ammonia solutions of increasing concentrations). For the liquid must, 200 mL was acidified (1% formic acid) and directly loaded on the resin.…”

“…3SPol, 3SHol and 3S4MPol S-conjugates were also quantitated in green malt I, according to the procedure previously described by Chenot et al (29) (data for grapes, hops and kilned malts obtained prior to this work (16,18,21,29)).…”

“…To obtain trans-2-heptenal or cis-2-octenal (compounds in hatched boxes in Figure 5), unlikely lipid oxidation pathways would be required, involving 10-, 11-or 12-hydroperoxides (minor (16,18,21,29). *value for Cys-3SHol+Cys-3S4MPol together.…”

Malt and Hop as Sources of Thiol S-Conjugates: Thiol-Releasing Property of Lager Yeast during Fermentation

“…Roland et al already evidenced in malt up to 6 μg·kg –1 Cys-3SHol and 700 μg·kg –1 G-3SHol. Yet as these compounds co-elute from most HPLC columns, an adapted procedure for distinguishing 3S4MPol from 3SHol conjugates was applied here. , …”