Understanding and evaluating the effect of wort boil time and trub levels on malt fermentability with the miniature fermentation

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.