Abstract
Hop oils contribute strongly to beer aroma, but their composition changes during fermentation and conditioning through yeast biotransformation, volatilization, oxidation, and adsorption. This study investigates hop oil transformation during fermentation and beer conditioning. Beer trials were prepared with controlled hop addition timing, yeast strain, fermentation temperature, and conditioning duration. Monoterpene alcohols, terpene hydrocarbons, linalool, geraniol, citronellol, myrcene, ester formation, dissolved oxygen, turbidity, and sensory aroma descriptors were measured. The results show that yeast activity transformed selected hop oil compounds into more aroma-active forms during active fermentation. Conditioning reduced volatile intensity through sedimentation, adsorption, and oxidation, especially when oxygen exposure was not controlled. Late hop addition improved aroma retention but increased sensitivity to storage conditions. The study demonstrates that hop aroma stability depends on managing both fermentation-stage biotransformation and conditioning-stage losses. Better control of yeast–hop interaction can improve aroma persistence and sensory quality in finished beer.