O-4
The relationship between the quality of 100% malt beer and the flavour
compounds of malt. Malt quality has a great influence on quality of beer, especially that of
100% malt beer. We found by sensory evaluation that a type of malt showed the
strong green grainy flavor. It seems that this flavor would be caused by the
malting process and carried through to the final beer. When beer has this
flavor, a negative character will be built up on the palate and decreases the
drinkability of beer. We assumed that this negative flavor of malt was related
to kilning conditions during malting. We thought that there was not enough
moisture in the latter stages of kilning, leading to restraint of chemical
reactions that decreased negative flavor and/or increased positive flavor that
would mask negative flavor. In order to improve malt flavor, we tried to
optimize kilning conditions and manipulated the air re-circulation and airflow
during the latter stages of kilning procedure. As a result, the negative green
grainy flavor of malt decreased and positive malty flavor increased. This could
be achieved without any change in malt specification (e.g., color, diastatic
power, extract) and efficiency of the kilning process. In order to investigate
the indicator chemical compounds of this negative flavor, we tried to analyze
heterocyclic compounds of malt samples. The content of some compounds was
clearly related to the change of kilning procedure and the sensory evaluation.
Especially, the content of 2-acetylpyrrole was higher in the malt produced
through optimized kilning conditions. 2-acetylpyrrole may be a useful indicator
compound of malt flavor quality. We performed brewing trials in the pilot plant
using two kinds of malt samples, produced through kilning conditions before and
after optimization. The sensory analysis of beer samples clearly showed that
decrease of malt green grainy flavor resulted in decrease of green grainy flavor
in beer and improvement of beer drinkability. As mentioned above, beer quality
was improved by improving malt quality through judicious manipulation of kilning
conditions.
Katsumi Oshita is a researcher in the Research Institute for New Product
Development of Suntory Limited. He earned his master's degree in food science
and technology from the Kyoto University in 1991, and joined Suntory Limited as
a researcher that same year. From 1991 to 1995, he was involved in the research
for improving fermentation performance of beer and whisky. Since 1995, he has
studied the relationship between malting conditions and malt quality. He also
has an interest in the relationship between malt quality and beer quality.
KATSUMI OSHITA, Masako Sawada, Akira Isoe, and Yasutsugu Kawasaki. Suntory
Limited, Research Institute for New Product Development, Mishima-gun, Osaka,
Japan.