Data from Small Mash Efficiency Experiments

[micraftbeer]

I recently moved from a single vessel eBIAB set-up to a 2-vessel set-up with one kettle a standard Mash Tun (MT) with no heating element, and the other my Boil Kettle (BK) that I was using just for boiling. My efficiency numbers were coming in lower than I expected so I set up a small experiment to try different variables I'd read people suggesting in HBT and other areas. I wanted to share my results to try to put some specifics behind the efficiency effects circulating out there. I also have the brew day length in mind, so I somewhat limited myself to a process time limit of no more than 30 minutes from end of mash to the collection of my full pre-boil volume.

For this experiment I went to my LHBS and weighed out equal amounts of grain and put them in their own bags so I knew for sure the weight was exactly what I wanted, and all of the grain came from the same batch.

My MT was a 15-gallon Spike kettle, with Spike's "V3" false bottom and center pickup tube from the center/bottom of the false bottom. I used a Blichmann 120V/2000W RIMS Rocket to control mash temperature.

I adjusted my brew water with my brewing salts to match my "Hop Forward" profile, and then I added Lactic Acid to hit 5.6 pH (measured) on each of the batches. In this small experiment I evaluated different sparge methods as well as grain crush. Measuring pre-boil gravity in the BK, I used BeerSmith mash efficiency calculations for the numbers below.

7 lbs 2-row
1 lb Crystal 40L
0.5 lb White wheat

Mashed @ 1.4 qt/lb for 60 minutes @ 150F
Sparge water @ 168F
Target pre-boil volume 7.5 gallons


Baseline Process
- Time from Mash end to pre-boil volume collected = 20 minutes
- 0.034" grain mill setting
- After mash complete, transferred full sparge water into MT, then pumped wort out of MT to BK.
- Measured mash efficiency = 70.4%

Single Batch Sparge Process
- Time = 23 minutes
- 0.034" grain mill setting
- After mash complete, drained off all wort from MT into BK, added full sparge water volume to MT and stirred, vourlaf, then drained off wort into BK.
- Measured mash efficiency = 75.3%

Single Batch Sparge Process + Finer Crush
- Time = 23 minutes
- 0.026" grain mill setting (had no stuck sparge issues or excessive grain bits in BK)
- After mash complete, drained off all wort from MT into BK, added full sparge water volume to MT and stirred, vourlaf, then drained off wort into BK.
- Measured mash efficiency = 82.7%

20-Minute Fly Sparge Process + Finer Crush
- Time = 28 minutes
- 0.026" grain mill setting (had no stuck sparge issues or excessive grain bits in BK)
- After mash complete, drained off wort until ~2" water level above grain bed, then continually pumped in sparge water while draining to keep water above grain (until sparge water empty).
- Measured mash efficiency = 83.9%

 

[doug293cz]

Interesting. You could have gotten even more data if you had measured the SG of the wort in the MLT at the end of the mash, as this allows you to calculate the conversion efficiency (percentage of the potential starch that actually converted to sugar) achieved in the mash. Since the effect of finer crush is to improve the conversion efficiency, it would have been nice to clearly demonstrate this. Since mash efficiency is equal to conversion efficiency times lauter efficiency, knowing both mash efficiency and conversion efficiency allows you to calculate lauter efficiency. The sparge method directly affects lauter efficiency, and again, being able to quantitatively demonstrate this would have been a plus.

Finally, any efficiency calculation is only as good as the weight, volume, and SG measurements used in the calculation. Uncertainties in those measurements, as well as grain potentials, and moisture content, result in most efficiency calcs on the homebrew level only being accurate to +/- 3% - 4% (or worse.) So, drawing conclusions based on differences smaller than ~4% is suspect.

Brew on

 

[micraftbeer]

efficiency calculation is only as good as the weight, volume, and SG measurements used in the calculation. Uncertainties in those measurements, as well as grain potentials, and moisture content

To eliminate/minimize the effect of these noise factors, I wasn't comparing BeerSmith predicted efficiency versus measured, I was just trying different process variables so I could compare back to my baseline. Also, since I bought all the batches of grain at one time, the variability of a particular batch of grain would've been present in all samples.

But I agree with your point that rather than the absolute value of efficiency %, the value here is the difference when compared between the different processes.