Program Book - Master Brewers Association of the Americas

P-191
Sensory detection thresholds of iso-α and tetra-hydro-iso-αacids
in lager beer evaluated by ASTM 1432
KATHRYN KOLPIN (1), Thomas Shellhammer (1)
(1) Oregon State University
Previous research in our lab has shown qualitative differences
between iso-α-acids (Iso) and tetra-hydro-iso-α-acids (Tetra).
Questions have been raised as to whether there are panelist-specific
sensitivity differences between these two compounds. The objective
of this study was to measure and compare the individual human taste
thresholds and group thresholds of Iso and Tetra in lager beer using
ASTM method 1432. Threshold values of Iso and Tetra have been
published using ASTM method 679, which is the rapid method for
determining group thresholds of added substances; however, ASTM
method 1432 is currently the standard method for determining
individual and group thresholds. In this study, 14 volunteers were
trained in 3 1-hour sessions to familiarize the panelists with the
samples and testing procedure. Six replications were completed
during testing, in which each panelist was presented with a series
of 6 3-alternative forced choice tests. All panelists wore nose plugs
to eliminate olfactory influences. A sigmoidal response was fitted to
each panelist’s Iso or Tetra concentration versus correct choice data,
and the detection threshold for each compound was determined
as the concentration where the panelist correctly chose the dosed
sample 66% of the time (50% above chance). Group thresholds were
determined as the concentration on a rank probability plot where
50% of the panelists could not detect the compound 66% of the time.
Confidence intervals (95%) were calculated for the group according
to a rank-probability plot. The group-wise detection thresholds and
95% confidence intervals of thresholds for Iso and Tetra were 7.1
ppm (4.5–11.2 ppm) and 2.7 ppm (0.7–10.0 ppm), respectively.
Katie Kolpin received her B.S. degree in food science at the University
of Wisconsin, Madison, in 2006. She currently works under the
supervision of Dr. Tom Shellhammer researching sensory thresholds
of hop compounds in foods. She plans to complete her M.S. degree in
food science and technology at Oregon State University in 2008.
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P-192
Ethical drinkability testing: A novel approach to measure
preference without exceeding government guidelines
DEBORAH PARKER (1)
(1) BRI, Nutfield, United Kingdom
As in any production industry, sales volume is a key success factor,
and the brewing industry needs to understand what makes one
product more drinkable than another. Drinkability may be defined
as ‘product preference after consuming a given quantity of the
product’. If the preference changes during the drinking experience,
then the product is deemed not to have a high drinkability. If
the preference does not change then the product has retained
its drinkability. Understanding why customers consume more
of one drink compared to another is a complex issue. We would
like to understand this process more clearly, but investigations
are hampered by ethical issues. In order to explore the concept of
preference in relation to beer, researchers will often use extended
drinkability testing. However, traditional extended drinkability
testing, whereby respondents are asked to consume relatively large
quantities of beer, can raise concerns over ethics. Is it acceptable
to ask respondents to drink in excess of their daily recommended
number of alcohol units? Using an alternative and novel method
of assessing drinkability developed at BRI, the desire to continue
drinking was investigated together with how preference changes
as beer is being consumed. The key factor for this novel method is
that the quantities consumed within the drinkability session remain
within ethical guidelines for moderate daily alcohol consumption
and is therefore a more acceptable method for such studies. This
method is a way of assessing a key sales parameter without upsetting
public morals and can also explore reasons whereby why some
consumers switch beer brands during a drinking session.
Debbie Parker is a sensory scientist. With a honors degree in
biochemistry and a Ph.D. degree in brewing science, Debbie is
a competent project manager for member companies, including
brand benchmarking, troubleshooting and flavor fault diagnosis.
Debbie is an accredited trainer who is experienced in the design
and delivery of sensory training courses and workshops relating to
the brewing industry in the United Kingdom and overseas. She has
given presentations at MBAA, Siebels Institute (Chicago) and EBC
conventions, and she is a member of the EBC Sensory Sub group
Committee. Debbie is knowledgeable about the brewing process
(Dipl. Brew.) and is a frequent lecturer at industry training courses
and technical meetings. Debbie also manages and trains the BRI
Expert, Technical, and QDA panels and is experienced in sensory
data manipulation, including multivariate statistical analyses. She
has been a professional beer taster for 18 years and invited judge at
competitions such as the Great British Beer Festival. Debbie has led
tutored tastings at the British Embassy in Stockholm for the BBPA
to promote British ales and has tutored tastings at the Bar and
Pub Exhibition, Olympia, on behalf of Cask Marque. Debbie is the
assessor of Cask Marque assessors. Debbie has also presented at
“Beer and Food Matching” sessions at the Cheltenham Festival of
Science and provided interviews for various food magazines and for
the BBC Radio 4 Food Programme.