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L 13
Principal components analysis of
aroma compounds in beer
Taku Irie 1 ,Yuichi Nakamura 1 , Yoshinori Ito 1
1Asahi Breweries Ltd., Tokyo, Japan
L 14
A new stable isotope dilution approach
for the sensitive quantitation
of 3-methyl-2-buten-1-thiol (MBT)
and its application to study sunstruck-flavour
development in beer
and its application to study sunstruck-flavour
development in beer
Susanne Stingl 1 , Peter Schieberle 1,2
1German Research Centre for Food Chemistry, Freising, Germany,
2 Technical University of Munich, Chair Food Chemistry,
Freising, Germany
L 15
A kinetic framework for the modelling
of beer flavour instability
Paul Hughes 1
1International Centre for Brewing and Distilling, Edinburgh,
United Kingdom
DESCRIPTION OF TOPIC:
In this study, we examined the possibility of
principal component analysis (PCA) to control
quality of beer flavour, through the interpretation
of the results about a number of aroma
compounds which are synthesized by yeast
metabolism.
We made PCA of 6 compounds (acetate esters
and higher alcohols) of a certain kind of our
product beer (n = 322). Then we assumed the
interpretation, by analyzing the correlation
between the PC scores and other parameters
and by test brews under various amounts and
timings of wort aeration which affect the ester
formation.
As a result the data are abridged into two
components, which are assumed to indicate
each of two steps of ester formation during
fermentation. And the results of test brews
suggest that this method could be possible to
describe and evaluate the conflicting effects
of oxygen on the each step, that is, acceleration
by the increase of the metabolic substances
and deceleration by the inhibition to
alcohol acetyltransferase.
DESCRIPTION OF TOPIC:
Beer, when exposed to sunlight, quickly develops
an unpleasant aroma, commonly referred
to as the “sunstruck-flavour”. This offflavour
is predominantly caused by skunky
smelling 3-methyl-2-buten-1-thiol (MBT), formed
in the course of a light induced reaction
involving isohumulone, riboflavin, and cysteine.
Due to its extremely low odour threshold,
even minimum amounts of MBT may have a
detrimental effect on the aroma of beer.
In order to get a deeper insight into the parameters
influencing MBT formation in beer
and other hop based beverages, we developed
a new method for its sensitive and reliable
quantitation. Using 4-vinylpyridine, MBT
was converted to its pyridinylethyl derivative,
which was finally analysed by LC-MS/MS. Following
the stable isotope dilution approach,
deuterium labeled MBT was used as the internal
standard. The method was then applied
to study the MBT formation in model systems,
depending on hop product, sulphur source,
and the presence of antioxidants.
DESCRIPTION OF TOPIC:
Many problems of flavour quality have not effectively
yielded to a solution, despite many
man years of effort. In part this is due to the
compositional complexity of beer, so that research
has necessarily focused on one or a
small number of issues. This is particularly
pertinent for beer flavour instability, where
effort variously focuses on oxygen, sulphite,
lipid oxidation, aldehydes, Strecker degradation
etc. Here we propose a framework for
addressing the connectivity of these various
elements at the chemical level, and identify
knowledge gaps that, when filled will enable
the prediction of the trajectories of beer flavour
deterioration with time. As an example
we will look in detail at the various routes of
sulphite loss during beer ageing and indicate
what would be required to minimise the rate
of sulphite loss.
Taku Irie
Susanne Stingl
Paul Hughes
He received a M.S. degree in engineering from
the University of Tokyo in 2000 and began
working for Asahi Breweries, Ltd.. After he
had worked in the packaging section at some
breweries to 2007, he started his career as
an engineer of technological development of
brewing at the Ibaraki R&D Promotion Office.
And since May in 2012, he has been working
as a guest researcher at the Chair of Brewing
and Beverage Technology, Center of Life and
Food Sciences Weihenstephan.
Born in 1984. Studied Food Chemistry at the
Technische Universität München (Technical
University of Munich) in Garching, Germany.
She graduated in 2008. Currently, she works
as a Research Scientist at the Deutsche Forschungsanstalt
für Lebensmittelchemie (German
Research Centre for Food Chemistry),
Freising-Weihenstephan, in the group of Prof.
Dr. Peter Schieberle. At the moment she is
about to finish her PhD studies on compounds
contributing to the sunstruck off-flavour in
beer.
Paul is a trained chemist and is currently Professor
of Brewing and Distilling at Heriot-Watt
University. He specialises in final beer quality,
sensory research/methodology, whisky maturation,
hop chemistry and business planning
for innovation. Paul consults regularly
for the food and drinks industries and has
published widely.
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