Yeast and Fermentation Session
ANKITA MISHRA, Dalhousie University, Halifax, Nova scotia, Canada
Co-author(s): Alex Speers, Dalhousie University, Halifax, NS, Canada
ABSTRACT: The basic aim of barley malt breeders and
maltsters is to produce malt with optimum fermentability levels, which
enables maximum alcohol yield from fermentable wort dissolved solids
(extract). This challenge includes understanding and assessing the
effects of physical processes involved in beer preparation such as wort
boiling and trub formation. The intent of this research was to
understand and evaluate the effect of wort boiling and autoclaving at
varying time periods (30, 45, 60, 90, and 120 min) on malt
fermentability. The effect of trub content was also analyzed.
Small-scale fermentations were carried out using a “reference malt” and
the now standard SMA yeast strain. The apparent degree of fermentability
(ADF), turbidity (absorbance at 600 nm) and density (°P) was measured
at specific time intervals over the 3-day fermentation period. The ADF
relates to the relative percentage or the extent to which wort is
fermented. The decline in density was modeled with the logistic equation
that predicts a sigmoidal shaped decline in density. Turbidity
measurements reflect the relative amount of yeast cells present in the
fermenting wort and can be modeled with a tilted Gaussian fit. The data
sets were then modeled and compared with ANOVA type analysis using PRISM
software. From the results obtained, we suggest that upon boiling the
wort without trub (at 100.2°C) for a range of times significant
differences in ADF are obtained (P < 0.05). All fermentation
runs, with and without trub, at lower boiling or autoclaving times were
faster than longer boiling or autoclave treatments showing steeper
extract curves when modeled. Malt fermentability also considerably
declined upon treatment of wort with high autoclave temperature and
pressure levels (121.1°C, 2 atm). The amount of trub formed after
boiling or autoclaving was found to be 0.2–0.32 g in 500 mL of wort. The
presence of trub gave mixed results. When wort was autoclaved, trub
significantly lowered (P < 0.05) the fermentation rate.
However, when boiled wort containing trub was fermented, no significant
difference in the fermentation rate were noted (P > 0.05).
Free amino nitrogen (FAN) level and wort color (EBC units) were also
determined and compared after each specific wort treatment.
Ankita
Mishra received her bachelor of technology degree in biotechnology from
the Vellore Institute of Technology, India, in 2009. She began her
master of science degree in food science at Dalhousie University in
2009. Ankita received Industrial training from Dabur Industries (India)
in plant biotechnology and quality control in 2008. She has previously
worked with Biostadt (India Ltd.) in quality assurance in manufacturing
bio-pesticides and related manufacturing processes.
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