Mash Yield/Fermentability Experiments

I have conducted some experiments on mash extract yield and fermentability as a followup to some work Dr. Fix reported on in Aug. 94 in HBD. I thank Dr. Fix for inspiration for this work and also for technical assistance in setting up the experiments and interpreting my results. I ran the experiments to determine the effects of the 40/60/70C mash program on yield and fermentability in my homebrewery. While I don't consider the results definitive in the realm of mashing grains, I do think they provide useful data on the effects of low temperature (40C/105F) mash rests and manipulating fermentability via 140F/158F mash rests.

Mash Yield Experiment

The following experimental mashes were conducted to determine the effects on extract efficiency in an infusion mash with the following options:

• 30 minute rest at 105F 'beta-glucanase/liquification of amylases'
• 15 minute rest at 165-170F 'Mash-out'

The following conditions were used for all experiments:

• Softened carbonate well water boiled 20 min. with 1.5 tsp. CaSO4 / 5 gal. to reduce carbonate/bicarbonate hardness. Used for mash and sparge.
• HDM Belgian Pale Ale malt - 2# grist per mash crushed w/ fixed roller JSP grain mill
• Total mash water = 1.25qts./lb. grist
• Sparge water = 165-170F / 1.4-1.5qts./lb. grist
• Total sweet wort runoff = 5-6qts. (2.5-3.0 qts./lb.)
• Sparge time = 10 min. to gather 5-6qts. runoff
• Lautering/Sparging conducted in 5gal. Gott cooler w/ false bottom
• Mash pH 5.3 - 5.5

1. Mash-in @ 155F - hold for 60 min. 'One-Step Infusion' extract efficiency = 55% = 1.024 s.g./lb. in 1 gal.
2. Mash-in @ 155F - hold for 60 min - boost to 165-170 F - hold 15 min. grist doughed in at mash water rate of 1.25 qts./lb. grist - external heat boost to 165-170F 'Step Infusion_MO' extract efficiency = 64% = 1.028 s.g./lb. in 1 gal.
3. Mash-in @ 105F (0.75 qts. water/lb. grist) - hold 30 min. - boiling water boost (0.5 qt./lb. grist) + external heat to 155F - hold 60 min. 'Step Infusion_BG' extract efficiency = 68% = 1.030 s.g./lb. in 1 gal.
4. Mash-in @ 105F (0.75 qts. water/lb. grist) - hold 30 min. - boiling water boost (0.5 qt./lb. grist) + external heat to 155F - hold 60 min. external heat infusion to 165-170F - hold 15 min. 'Step Infusion_BG_MO' extract efficiency = 71% = 1.031 s.g./lb. in 1 gal.

Conclusions: Yield Experiment

• In this experiment, a 30 min. rest at 105F was more effective in increasing yield than a 15 min. 165-170F mashout rest.
• In this experiment, when a 30 min. rest at 105F was employed, only a minor increase in yield was obtained with a 15 min. 165-170F mashout rest.

Fermentability Experiment

Several experimental mashes were conducted to evaluate the effects on fermentability of 140F/40C rests of 0 min, 15 min., and 30 min. using a 40/60/70/75 mash program.

Details of this experiment are as follows:

• Mash conditions from Extract Efficiency experiment were used
• A large amount of M&F dried yeast (2 grams /qt.) was pitched to insure complete fermentation
• 20 oz. experimental worts were fermented for 3 days at 66-68F in Korbel (squat) champagne bottles.

Worts from the following three mashes were fermented:

Mash Rest Temp.105F/40C	140F/60C	158F/70C	167F/75C
Fermentability
High		30 min.	30 min.		30 min.		15 min.
Medium		30 min.	15 min.		45 min.		15 min
Low		30 min.	-		50 min.		15 min

Fermentation results are summarized below:

Fementability	Original Gravity	Final Gravity	Apparent Attenuation
High		1.052			1.017		67%
Medium		1.054			1.019		65%
Low		1.050			1.019		62%

Conclusions: Fermentability Experiment

• Apparent attenuation trend matched expectations.
• Apparent attenuation could be further increased by a 45-60 min. rest at 140F prior to the boost to 158F.
• Apparent attenuation can be decreased through the addition of specialty malts such as dextrin or crystal malt.