Yoshimasa Taniguchi (1),
Yuji Kaneko (2), Mikio Katayama (2), Yasuji Kawachi (2), Fumitoshi
Manabe (3); (1) Central Laboratories for Key Technologies, Kirin
Company, Limited, Yokohama, Japan; (2) Research Laboratories for Health
Science & Food Technologies, Kirin Company, Limited, Yokohama,
Japan; (3) Research Laboratories for Beverage Technologies, Kirin
Company, Limited, Yokohama, Japan
Hops
Poster
Isomerized hop extracts and chemically modified reduced hop extracts
that contain highly pure iso-alpha-acids and reduced iso-alpha-acids,
respectively, have been widely used for brewing to add bitterness and
improve beer quality. These components have also received considerable
attention because of their multiple bioactivities. However, their
intense and sharp bitterness make it very challenging for them to exert
potential benefits. Humulinic acids (HAs), which are derived from
alkaline hydrolysis of iso-alpha-acids, have been reported to be
strongly less or non-bitter. In this study, we aimed to develop a novel
hop extract comprised of HAs. HAs were quantitatively generated with
fatty acid by-products, 4-mehyl-3-pentenoic acid and
4-methyl-2-pentenoic acid, by alkaline hydrolysis of isomerized hop
extract. The fatty acids had a very unpleasant odor and made it
difficult to use the hydrolyzed extract as a food additive. A very
simple and effective method to separate HAs from the fatty acids was
successfully developed. Addition of a divalent metal ion, such as
magnesium, to the hydrolyzed extract formed precipitate of HAs, and the
fatty acids could be completely removed by filtration. Washing the
HA–metal ion complex with acidic water yielded a yellow solid of free
HAs. An aqueous solution of highly pure, concentrated potassium salt of
HAs could be obtained by addition of potassium hydroxide and/or
potassium carbonate. The appearance of the obtained HA extract was
similar to aqueous isomerized hop extract but had markedly reduced
bitterness. The stability of the extract was very good, and no
degradation of HAs was observed for at least 4 months in an acceleration
test at 60°C. Furthermore, HAs in a model beverage solution (pH 4.0)
containing the extract were stable during storage for 2 months at 35°C.
The less-bitter character and high stability of the developed extract
may lead to practical use of the extract to improve beer quality and as a
potential bioactive agent.
Yoshimasa Taniguchi graduated from the Department of Agriculture
at Kyoto University in Japan in March 2006. He began his career in the
Central Laboratories for Key Technologies at Kirin Company, Ltd. in
April 2006. He has investigated hop chemistry in the laboratory since
2009.
