The change of monoterpenoids during fermentation and their contribution to hop aroma of beer

Monoterpenoids,such as linalool,geraniol and β-citronellol,are important compounds in beer and their changes during fermentation have effect on the beer aroma directly.In 4%(v/v) ethanol solution,it was found that single compound and mixture with linalool,geraniol and β-citronellol in different concentration both have different characteristics by sensory evaluation and statistics.When their concentration were no more than 50 μg/L,it's not necessarily that there was stronger hop aroma in beer with their higher concentration,and the synergy of three compounds had the strongest hop aroma with 12.5 μg/L of linalool,12.5 μg/L of geraniol and 25 μg/L of β-citronellol.In addition,biochemical changes happened during fermentation,and linalool was converted into α-terpineol,geraniol was converted into β-citronellol rapidly and β-Citronellol was converted into citronellyethanoate.Generally,the loss rates of them were 36.6%,45.1% and 38.1% respectively.Sum up,it was probable to get the outstanding hop aroma in beer by adding appropriate amount of hop during brewing and controlling the final concentration in beer with 12.5 μg/L of linalool,12.5 μg/L of geraniol and 25 μg/L of β-citronellol.