Investigation of Geraniol Biotransformation by Commercial Saccharomyces Yeast Strains by Two Headspace Techniques: Solid-Phase Microextraction Gas Chromatography/Mass Spectrometry (SPME-GC/MS) and Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS)

Hop-derived volatile organic compounds (VOCs) and their transformation products significantly impact beer flavour aroma. Geraniol, a key monoterpene alcohol in hops, has been reported to undergo yeast-modulated biotransformation into various terpenoids during fermentation, which impacts the citrus floral aromas of finished beer. This study monitored evolution geraniol its throughout fermentation provide insight differences as function yeast species strain. The headspace concentration VOCs produced model wort was measured using Solid-Phase Microextraction Gas Chromatography/Mass Spectrometry (SPME-GC/MS) Proton Transfer Reaction-Time Flight-Mass (PTR-ToF-MS). In absence yeast, only detected, no terpenoid were detected geraniol-free ferments. During depletion closely followed by detection citronellol, citronellyl acetate geranyl acetate. formation behaviour strain dependent. SPME-GC/MS provided confidence compound identification. PTR-ToF-MS allowed online monitoring these products, showing when differed between Saccharomyces cerevisiae pastorianus yeasts. A better understanding ability different biotransform hop terpenes will help brewers predict, control, optimize aroma