Control of hop aroma in beer by hop boiling conditions

MARIKO ISHIMARU (1), Takako Inui (1), Kaneo Oka (1), Nobuyuki Fukui (1)
(1) Suntory Liquors Ltd., Beer Development Department, Mishima-gun, Osaka, Japan

Linalool is an important hop aroma compound in beer. Therefore, it is essential to control the concentration of linalool in beer for achieving the target quality, particularly the hop aroma, stably. In order to rationalize the factors which may affect the concentration of linalool during the boiling process, we have carried out model boiling tests under various conditions as follows: 1) the timing of the late hopping, 2) the gravity of the wort, 3) the pH of the wort, and 4) the malt ratio of the wort. The concentration of linalool in the boiled wort was analyzed. We also have focused on hop aroma compounds other than linalool to evaluate their organoleptic characteristics in beers. The isomerization rate of the α-acids and the amount of hop bitter compounds were also examined carefully, because we have observed a case where the isomerization of the α-acid was incomplete as a result of insufficient boiling time. From this information, it is suggested that the characteristics and the intensity of the hop aroma in beer would be controllable by adjusting hop boiling conditions.

Mariko Ishimaru received her M.S. degree from the Department of Agriculture, Kyushu University, and has been engaged in research on the improvement beer quality through hop science at the Beer Development Department of Suntory Liquors Ltd. since 2008.