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Sudden Drop in Brew House Efficiency...

bobo1898

Grandmaster Brewer
Master Brewer
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Jul 26, 2012
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I'm sure there are plenty of "how do I bump my efficiency" questions but I have suddenly come across a head scratcher with my brewing system.

When I started to pay attention to BH efficiency (3-4 years ago), I had pretty constant numbers:

Paler beers hit 72-75% efficiency. Darker beers hit 82-84% efficiency.

I was using my tap water (Chicago) with no treatment except for a camden tablet. For years my efficiency stuck within these numbers. Last year, suddenly, my numbers dropped:

Paler AND darker beers hit 59-65%.

My equipment has not changed. I, for the most part, hit my temp aside from the occasional not low enough temp, in which case I stir down to the target temp. Over the course of the 60-90 minute mash, I occasionally lose one to two degrees. The water, while not exact every time, has been very consistent given the chemical analysis report. I mill at my LHBS and it appears that the crush is correct. I spoke with them about it and we determined that it was possibly my mash pH that was the problem. Even though I had better efficiency before and the water was fairly constant, I figured that it was still possible. Regardless of this conversation, for the last year, I had been taking pH readings anyway to see where I stood at mash pH as I was starting to understand water treatment. On average, I was at 5.4-5.7.

The last three batches that I made, I actually treated my water beyond the camden tablet with gypsum, calcium chloride and lactic acid. I made a saison (6.8 SRM), stout (43 SRM) and IPA (7.6 SRM). My efficiencies were:

Saison - 69.8% (did not take a mash pH reading)
Stout - 65.1% (mash pH 5.40)
IPA - 59.4% (mash pH 5.46)

Does any of this make sense? I still have my suspicions about the crush but in appearance it looks correct. It's a bit frustrating cause I'm missing my target gravities by 10-15 points.

Any possible explanation in why a constant brewing system would drop in efficiency?
 
Things I would check into:

1.  Crush

2.  Crush

3.  Crush

Seriously, a drop change that dramatic is most likely to a change in the level of intact grain kernels in your crush.  It may look the same, but take a ounce or two of your next grain batch and spread it out on a dark surface.  Separate all the kernels which look to be intact.  Gently pinch them between finger and thumb to see if they fracture easily or are basically untouched.  If you have a decent crush, you should have very few (if any) kernels which are intact and will not break apart with a little pinch.

Compare the amount (weigh the intact kernels versus the rest) with the rest of the grist.  Do this a couple of times and you should get an idea of your current grind quality.  Have your LHBS double grind another recipe and compare both the quality of the crush and the resultant efficiency of your process.

 
Thanks, Oginme.

Figure it will be the crush. My next thought was to double mill it at the store. I might just go ahead and do that, then check. Should I be concerned about obliterating the existing kernels that are crushed?

If I do find intact kernels, you're saying they should fracture easily upon inspection?
 
Ideally, a good crush leaves the husks intact, so many times there are seemingly intact kernels with fractured grain particles still inside.  These will usually break apart easily in the mashing in process or at the very least, have more surface area exposed in the particles to allow for easy extraction of the starches.  A light pinch will differentiate between kernels which have been shattered on the inside and those which are intact. 

The issue with the intact kernels is that the water cannot penetrate as quickly, nor the soluble starches be extracted quickly, to give you a good conversion efficiency. 

 
I mill my own grains with a Cereal Killer mill and generally grind quite fine (rolls set at .030, measured with feeler gauge, grain conditioned with 2% added water).  I did not
check my gap regularly until one of my batches came back with about a 65% efficiency.  I went back and checked and sure enough the rolls had separated some. After resetting, subsequent batches have generally been over 75%. I currently have the rolls set at .033 as I had one stuck sparge on .030.  So I agree with Oginme, check the crush.  You can get pretty aggressive before you experience a stuck sparge.
 
Sounds good, guys. Thanks for the responses.

I'll go ahead and check on this in a couple weeks when I brew next.
 
I must concur with the others. 15 years of brewing and when I see that dramatic of a change it has to do with crush
 
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