All Grain Brewing: Grain Crush and Efficiency

When brewing all grain, there are two things that will affect your efficiency more than anything else: grain crush and sparge technique. Grain crush affects your conversion efficiency while sparging affects your sparge efficiency. I'll be talking about sparge technique later, because grain crush is far and away the most important.

The finer your grain is crushed, the more easily the water and enzymes will reach the starchy goodness in the middle of your grains. A whole grain will go mostly unconverted, or require many hours to convert. Grain flour will convert in minutes. The ideal is to get somewhere in between these two extremes.

100% efficiency is attained by crushing the grain to flour in an ideal 'laboratory' setting. This includes the husks, and produces disgusting beer. Tannins are enzymatically extracted from the husks, and traditional sparging is impossible.

A bad crush, where about half of your grains are still whole, will probably get you about 50% efficiency. This was the case in my first two all grain batches, where I was lucky to get over 55% even though I mashed for over two hours.

Adjusting up and down between fine and coarse crushes is a tradeoff between higher efficiency versus difficulty sparging. Fortunately for us, we don't do traditional sparges in Brew in a Bag mashing. The problem in a traditional sparge is that if your crush is too fine, water won't be able to flow evenly through the grain bed. If you're lucky, you will get uneven rinsing. If you're unlucky, the sparge will get stuck. You'll have to mix everything back up, vorlauf again, and try again. You'll end up with so much extra water you'll have to boil for 3 hours. This sucks pretty hard.

When doing BIAB, we 'sparge' by soaking the grain bag in hot water for ten minutes and draining it. We repeat this as many times as we like to achieve maximum efficiency. Sparges don't get stuck. That means we prefer a very fine crush. Flour is fine, as long as you mix it in thoroughly so you don't have balls of dough. There is danger of shredding the hulls if you use certain types of mills, crush too fine, or use something like a food processor or blender to crush your grain. Remember, you are *crushing* your grain, not grinding or blending it!

If you have your own grain crusher, adjust your grinding plates so the endosperm (center of the barley grain) is crushed very fine (many small pieces, or some flour). Don't create too much flour, because it becomes hard to mix in. 20-30% flour is okay. Also don't let your hulls get too small or shredded.

If you crush your grain at your LHBS, ask them to adjust the mill to its finest setting. Then, run it through twice. The second crush won't make it any finer, but it will make 100% sure that no whole grains made it through.

After asking my LHBS to adjust the crush (someone had messed with the mill without them knowing), my efficiency jumped from 58% to 90%. I've since seen efficiency as high as 93-95%.

(Mike McDole mentioned this on one of the brewing network podcasts a while back. He likes his grain crushed very coarsely, and he said that MoreBeer had its grain mill set on the "Tasty" setting for a while. I couldn't stand it!).