P-1
The influence of raw hop storage condition on the quality of hops and
beer. From the brewer's standpoint, the most important hop components consist of
bitter substances, oils, and polyphenols. In Europe, there was no cold storage
warehouse for raw hops after harvesting until quite recently. Therefore we were
afraid of changes in the quality of raw hops during storage. The constituents of
hops are affected by oxygen, temperature, storage time, and humidity. It has
been reported that cold storage of hops avoids the reduction in alpha acids
normally associated with room temperature storage. We conducted the storage test
of raw hops under laboratory and normal warehouse conditions to examine the
effect of storage temperature on hops and beer. In the laboratory tests, we
evaluated the common indexes used to determine hops and beer deterioration and
decided whether we could use them. In the normal warehouse tests, we examined
the changes in quality under actual conditions to determine the effectiveness of
using the above indexes. In the laboratory, we used the Magnum, the Hersbrucker,
and the Saaz; the hops were stored at 4, 15, and 30°C for 5 months. We then
examined the changes in hops and beer quality with deterioration indexes.
Regarding deterioration indexes for hops, we determined alpha acid content using
the HPLC method and LCV, the ratio of the former to the latter (HPLC/LCV ratio),
the Hop Storage Index (HSI), and Hop Deterioration Index (HDI). Consequently
with increasing temperature, we found a wider difference in the indexes.
Therefore the storage temperature affected hops quality, and the foregoing
methods were adopted as deterioration indexes for hops. We brewed with the
stored hops in 200-L pilot plants, and examined the effect on beer quality. As
to deterioration indexes for beer, we evaluated the ratio of iso-alpha-acid
content to bitter units, polyphenols, anthocyanogen, and low molecular
polyphenols by the HPLC method. Also, beer quality was evaluated by sensory
analysis. We found changes in the indexes for taste and aroma. The storage
temperature affected the beer quality, and we adopted the foregoing methods as
deterioration indexes for beer. In the normal warehouse tests, Japanese
Shinshu-Wase, were used and stored at 4°C or normal temperature for 5 months. We
obtained almost the same results as in laboratory tests, indicating that the
storage temperature affected the hops and beer quality under actual conditions.
We should determine whether to use cold storage warehouse or normal warehouse
from the viewpoint of costs and quality.
Tsunehiro Ikeda received a Master of Agricultural Chemistry in Kyoto
Prefectural University. In April 1988, he began to work at Non-Alcholic Beverage
and Foodstuffs Research Laboratory as an analyst in Asahi Breweries, LTD. He has
studied Bremaster course as a guest student at Weihenstephan University in
Germany (1997-1998). In the Hallertau hop cultivation area in Germany he has had
a practical training in analysis, cultivation, and production of hops. Since
1998 he has researched hops in the Brewing Research and Development Laboratory,
Ibaraki.
TSUNEHIRO IKEDA (1), Toru Kishimoto (1), Atsushi Suzuki (1), Tomoki Nanba (2),
Nobuo Kaji (1), Yutaka Miyamoto (1), Tomomichi Oga (1), Kazunori Shibata (1),
and Katsuyuki Kawatsura (1). (1) Asahi Breweries, Ltd., Moriya, Ibaraki, Japan,
and (2) Asahibeer Malt, Ltd.