Yeast and Fermentation Session
Joshua Adler, Dalhousie University, Nova Scotia, Canada
Co-author(s): Alex Speers, Dalhousie University, NS, Canada
ABSTRACT: Premature yeast flocculation (PYF) is a burden
on the malting and brewing industries. It causes production difficulties
and quality issues characterized by high sugar concentrations and low
yeast cell counts post-fermentation. This results in variability in
fermentation and flavor profiles. For this reason it is critical for
brewers to assess their malts for PYF potential. To test for PYF
potential in malt, the industry relies on a variety of fermentation
assays. These methods can indicate if a sample displays PYF, but they do
not determine the threshold at which PYF occurs. This study used
modified miniature fermentations to investigate how a concentration of
known PYF malt can influence the fermentation. Using wort prepared from
varying ratios of control and PYF malts the change in absorbance and
Plato was monitored. In addition, a PYF factor was extracted and used in
varying amounts in a synthetic wort (i.e., malt extract) and fermented.
While it is difficult to specify the actual amount of PYF factor
extracted, this “PYF solution” was used in a second experiment to make
up synthetic worts at levels of 0–100%. These trials were conducted
using a 15 mL fermentation with a consistent temperature and pitch rate
(21°C, 1.5 × 107 cells/mL). At designated intervals
throughout each fermentation, yeast in suspension was monitored
spectrophotometrically at 600 nm, and the apparent extract was measured.
It was found that varying the ratio of either PYF malt or the amount of
PYF factor could influence fermentation behavior. In the first
experiment, low PYF malt levels (i.e., 20 and 40%) had no significant
difference (P > 0.05) on absorbance. However, significantly different absorbance measurements (P
< 0.05) were found when using concentrations of 60% PYF malt or
higher. In the second series of experiments no difference from the
control to the PYF solution at strengths of 20, 40, and 60% was observed
(P > 0.05). But, significantly different fermentations (P
< 0.05) were noted when malt extract was prepared with 80 and 100%
PYF solutions. These findings agree with previous work but also suggest
that PYF malt may be blended with typical malt as long as a critical
threshold is not exceeded. This technique provides the brewer with
another tool for making informed decisions when managing their process
stream. Further statistical analysis of extracted measurements will also
be presented.
Joshua Adler received a B.S. degree in biology
from Dalhousie University in Halifax, NS, Canada. While pursuing his
degree he became very interested in food science and was the first
Dalhousie student to gain a minor in the discipline. His undergraduate
thesis focused on problems encountered in wheat beer production ,which
he presented at the 2011 ASBC Annual Meeting. Josh is continuing his
brewing research as an M.S. candidate at “Dal” and hopes to contribute
innovative findings on the fermentability of malt, as well as pass on
valuable knowledge as a teaching assistant in product development and
quality assurance courses. When outside the laboratory, Joshua can
usually be found in the boxing ring training for an upcoming bout or
enjoying a pint with his friends. One of his life’s ambitions is to
visit as many of the worlds’ brewing and distilling regions as possible.
He recently returned from the Lowland region of Scotland, where he
visited a variety of breweries and distilleries.
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