Program Book - Master Brewers Association of the Americas

P-189
Influence of non-volatile beer constituents on the bitter taste
perception of iso-α-acids
STEFAN HANKE (1), Werner Back (1), Martina Gastl (1)
(1) Lehrstuhl fuer Technologie der Brauerei I, Freising, Germany
The hop derived bitter taste is one of the most important and
most intrinsic properties of beer. The main bittering sources are
the iso-α-acids and in the case of the use of downstream products
derivates of the iso-α-acids, which are responsible for most of the
perceived bitterness. In addition to the concentration of the bitter
principles there are further factors influencing the perception of
beer bitterness. Because of the complex mixture of ingredients
beer can possibly mask some taste and flavor compounds. Masking
is a widespread phenomenon and a typical effect in heterogeneous
mixtures, like beer. There are different theories about the
contribution of ethanol, dextrins and pH-value on the bitter taste
perception of beer. The perception of bitterness and the harmony
of all ingredients is assumed to have a great contribution on the
drinkability of beer. Drinkability means a specific harmony of
all antagonistic substances in the beverage. It is influenced by
technological and non-technological (physiological) parameters.
One of these technological parameters is the composition of the
beverage. Changing the composition of a beverage has a great effect
on the perception of bitterness. In our experiments we changed
the composition of model solutions and of an unhopped lager. In
aqueous model solutions dextrins had masking properties and
increased the threshold of iso-α-acids. In an unhopped beer they
showed the same pattern. Dextrins may act as masking agents in the
beverage and are an antagonistic part of the bitter taste. Ethanol has
for some tasters a bitter taste. This results in a decreased perception
of bitter acids in the beer, so the thresholds increase. But it seems
that the bitter taste of ethanol itself is reduced by other constituents
in the beer. So we claim that ethanol, dextrins and the acidity of a
beverage have a great impact on bitter taste perception. A harmonic
composition of these factors is essential for beverages with a high
drinkability.
Stefan Hanke was born in 1980. From November 1999 to July
2004 he studied brewing science and beverage technology at
Munich Technical University (Weihenstephan), graduating as an
engineer with a Dipl.-Ing. degree. During his studies he worked for
and received practical training at different German brewing and
malting companies. Since September 2004 he has been a scientific
employee at the Lehrstuhl fuer Technologie der Brauerei I, Freising-
Weihenstephan, Germany (Professor Back). From December 2006
until May 2007 he headed the institute’s Small Scale and Pilot Scale
Brewery Department. Since May 2007 he has been responsible for the
HPLC and GC Laboratory of the institute. His main research topics
are the influence of hops on beer drinkability, as well as the influence
of beer matrix on bitter taste.
P-190
Identification of aroma compounds associated with sourness
KEIKO ISHIKAWA (1), Masato Kawasaki (1), Takeo Imai (1),
Yutaka Ogawa (1)
(1) Kirin Brewery Co., Ltd., Yokohama-shi, Japan
Beer aroma is comprised of various compounds, the balance of
which is very important to taste profile. Consumer research reveals
that indications of sourness can decrease taste preferences. It is
conceivable that the sour aroma in aroma components may be a
contributing factor, separately from sour flavors represented by
organic and inorganic acids. Depending on the concentration
levels, this sour aroma may be characterized as odorant. To improve
beer flavor requires that the aroma associated with this sour odor
be controlled. In our research, we utilized GC-olfactometry in
an attempt to identify compounds associated with sour odors in
beer. As a result of our research, we were able to detect at least 10
components linked to sour odors, mainly odors associated with fruit,
cheese or natto. Using GCMS, we were able to identify aliphatic
acids, aliphatic acid esters, and higher alcohols. For several of these
compounds, we were able to confirm an identical aroma between
a reference standard and our GC-olfactometry. These compounds,
either individually or in combination, may contribute to sourness in
beer.
Keiko Ishikawa graduated from the Department of Food Science
(dietician course) of the Otsuma Women’s University, Faculty of
Home Economics, in 2002. She joined the Kirin Brewery Co., Ltd.
Research Laboratories for Brewing that same year and, for the next
four years, worked in beer instrumental analysis. During 2006, she
started work in brewing technology development, and at present, she
is engaged in microanalysis, focused mainly on odor substances.
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