CYNTHIA ALMAGUER (1), Thomas Becker (1), Martina Gastl (1)
(1) Technische Universität München-Weihenstephan, Lehrstuhl für Brau- und Getränketechnologie, Freising, Germany
At its most simple, hop (Humulus lupulus L.) varieties are
classified, according to their flavoring properties, as ‘bittering hops’
and ‘aroma hops’. In numerous studies, detailed assessments of the
quality parameters of both types have been carried out. Usually,
bittering hops and aroma hops are compared and rated based on their
brewing value and their contributions to beer quality. The brewing value
of hops is primarily attributed to the flavor- and bitter-active
compounds found in the resins. These resins are synthesized and
accumulated in the lupulin glands of hops. Early work on the
fractionation of hop resins, based on the solubility of resins in
various organic solvents, classified them into soft resins and hard
resins. Until now, research has primarily focused on studying the impact
on beer properties of the major hop bitter acids (α- and β-acids)
present in the soft resin. For this reason, little information is
available on the functionality of the hard resin and for years it has
been considered of no value. However, it is known that, besides the
α-acids, hops contain other constituents which can contribute to beer
quality. It is the purpose of this work to determine the extent to which
the hard resins contribute to the beer quality. Additionally, it is
intended to establish if there are any significant differences among the
hard resins extracted from the different hop varieties. Further, the
functionality of this resin as a brewing product is examined, and
finally the hard resin contribution to the microbiological stability of
beer is assessed. To achieve all these, brewing trials were conducted in
which the α-acids were replaced with a hard resin rich extract. In
these laboratory-scale experiments, it was possible to determine that
the hard resin contributes to the microbiological stability of beer.
Furthermore, it was shown that addition of this resin confers a pleasant
bitterness and a desired hoppy flavor which is a great contribution to
the harmony and drinkability of beer.
In 2008, Cynthia Almaguer completed her B.S. degree in biochemical
engineering at Jacobs University, Bremen. She then started her graduate
studies in a collaborative project between the Institute of Brewing and
Beverage Technology (Professor Thomas Becker), TUM-Weihenstephan and the
Department of Food and Nutritional Sciences (Professor Elke Arendt),
University College Cork. Her research project aims to understand and
reveal the contributions of hop hard resins in beer. A significant
portion of her research activities are directed toward the investigation
of the taste as well as the antimicrobial properties of hops.
