Mash Efficiency Tests… The problem with store milled malt

Stored milled grain is notoriously under crushed. The general theory on this is that shops under crush to prevent stuck mashes. I think that’s true but I also wonder if it’s to prevent wear and tear on their equipment and potentially mill faster.

Side by side crush tests

These are side by side mash tests using default setting of a homebrew scale grain mill vs store crushed grain.  The Rahr 2 Row both milled and unmilled were sourced at a reputable local homebrew shop.  Note that it did not come from Northern Brewer.  To produce as consistent results as possible, I measured everything (water and grain) in grams to the nearest single gram.



Procedure:

  1. Weigh 906 grams (1.997 lbs) of grain
  2. Weigh 2,715 grams of strike water (.717 gallons)
  3. Heat up strike water to 162 deg F.  Overheat by a degree or so and then stir back down to temperature.  It’s easier to hit a stable temp going down vs hitting it going up.
  4. While strike water is heating pre-heat mash tun with 1/2 gallon of 212 deg F water.
  5. Place grain (inside of bag) in cooler.
  6. Add strike water.
  7. Stir and record temperature.
  8. Mash for 60 minutes.
  9. Drain first runnings.
  10. Grain back in mash tun.
  11. Add 1,884 grams (.497 gallons) of 212 deg F water to the grain and stir.  I normally would not sparge with boiling water.  I used boiling water to take one more variable out of the equation.
  12. Drain second runnings.  Let grain bag sit on strainer for 5 minutes.
  13. Record volume and gravity.


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Each test used 906 grams (1.997 lbs) of grain using my trusty Escali Primo digital scale.


Each Test used 2,715 grams of strike water (.717 gallons).  For some reason I didn’t use the tare feature when I weighed the water.  The pitcher ways 547 grams.  That makes the water 2,715 grams.



81ZONpZSWNL._SL1500_This 2 Gallon Rubbermaid Cooler Served as a Mash Tun.  I used a paint straining bag to contain the grain.  This process worked pretty well.  This would be good equipment and technique to use for small batch all grain brews.  For consistency, I pre-heated the cooler prior to placing grain and strike water into it.


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A 5 gallon paint straining bag contained the grain.

My Thermapen reading mash temperature.  The temperatures of each trial mash were close but not identical.  One read 151.5 deg F, the other read 152 deg F.  I consider that to be within the limits of what I can test and produce in my kitchen.

Store Milled Grain Results

Store Milled Grain

Collected Wort.  With the help of an on-screen ruler, I’m going to estimate this at .859 gallons collected.  That means that .355 gallons were absorbed.  Making the absorption rate for this grain and crush .177 gallons/lb.


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My Atago PAL-1 Digital Refractometer reads 10 Brix.  That’s on OG of 1.040.  Rahr 2 Row should provide 37 points per lb.  That means there are a total of 74 points in the two lbs of grain I used.  .859 gallons of 1.040 wort comes out to a total of 34.375 points or an efficiency of 46.4%.  That’s low.  Although, the point of this particular experiment is to compare two grinds, not to measure the efficiency of one technique vs another.

Self Milled Grain Results

Milled GrainCollected Wort.  I’m going to estimate this at .875 gallons collected.  That means that .339 gallons were absorbed.  Making the absorption rate for this grain and crush .170 gallons/lb.


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My Atago Pal-1 Digital Refractometer reads 13.2 Brix.  That’s on OG of 1.053.  Rahr 2 Row should provide 37 points per lb.  That means there are a total of 74 points in the two lbs of grain I used.  .875 gallons of 1.053 wort comes out to a total of 46.375 points or an efficiency of 62.6%.  Again, the point of this particular experiment is to compare two grinds, not to measure the effectiveness of a particular set of equipment or technique.Store milled grain (left) vs self milled grain (right). Click to zoom.

Mash Test Conclusion:

  1. The store Milled Grain I used produced an efficiency of 46.4% vs an efficiency of 62.6% when using the default setting of my homebrew mill. That’s a comparative improvement of 34.9%.
  2. The default setting of the grain mill I used produced a great crush. If it hadn’t it could have been adjusted to be more aggressive.
  3. Grain crush is a big part of efficiency. Store crushed grain can be on the under crushed side.  Some stores do this to help prevent stuck sparges.  That’s a valid strategy and it may be way you want.
  4. If you are looking for more control over your mash milling your own grain provides you with quite a bit more control.  It also allows you to buy grain in bulk and crush right before brewing.  That preserves freshness and leads to better tasting beer.

In fairness this was the test of one specific malt from one specific homebrew shop. Results are going to vary. However, this test reinforces what I would call a general belief in the homebrewing community and it also matches my personal experience. Homebrew shops often under mill malt.

Benefits of Milling Your Own Grain

  1. Control Crush: Milling your own grain gives you control over the crush of your grain.  That’s a big factor in efficiency.  Many homebrew shops tend to under-mill grain to protect against stuck mashes.  I’ve seen pre-milled grain wildly-undermilled.
  2. Fine Tune Your Process, Improve Repeatability: A mill allows you to fine tune for your equipment and process.  You know what the crush is going to be since you set it.
  3. Save Money: A mill allows you to save money by buying whole bags of grain at a discount.
  4. Fresher, Better Tasting Beer: The shelf life of unmilled grain is longer than pre-milled grain.  Freshly milled grain = better tasting beer.

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Make sure the components you use are compatible and rated for your intended application.  Contact manufacturer with questions about suitability or a specific application.  Always read and follow manufacturer directions. tag:lnksfxd top:graincrush tag:tpr

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