Interactions Between Fermentation Temperature and Yeast Strain: Impacts on Polyfunctional Thiol Release and Beer Aroma

The biotransformation and release of polyfunctional thiols (PFTs), including 3-sulfanylhexan-1-ol (3SH), 4-methyl-4-sulfanylpentan-2-one (4MSP), and 3-sulfanyl-4-methylpentan-1-ol (3S4MP), contribute to tropical fruit aromas in beer. This study examines the effect of fermentation temperature (15–30 °C) on PFT production across five commercial yeast strains. Pilot-scale beers were brewed with Cascade hops and analyzed for 29 aroma compounds. A strong temperature-dependent increase in 3SH (33–72%) was observed, with the lager yeast strain yielding the highest levels at the high-temperature condition (30 °C). However, sensory analysis indicated that elevated thiol concentrations alone did not enhance tropical aroma. Instead, increased levels of β-ionone, β-damascenone, acetate esters, and terpenoids at higher fermentation temperatures correlated with a more pronounced tropical character, particularly with the ale yeasts. These results highlight the intricate relationships between thiol levels and concurrent volatile compounds, emphasizing that elevated thiol presence alone does not directly translate to heightened tropical aromatic expression in beer.