Can Grain Crush Really Affect Gravity That Much?

[sobiesk2]

This is my first post, i've brewed a few all grain batches and just ran into a major problem on my last 2. Both grain bills were purchased at the same time, and milled on the same mill. The first beer I noticed i was way off on my pre-boil gravity, like 20 points off. I ran to the store for some DME and fixed it, though I don't know how that will turn out.

I figured it was probably a bad job sparging, or I forgot to stir the mash or something, so on the 2nd I decided to do as a no-sparge batch. (mind you I can only do this because I struggle with efficiency in the past and bought extra grain this time)

So I did the 2nd batch, and stirred thoroughly with a roughly 2.4 qt to lb of grain ratio. No temp problems, finished around 148 started at 154. I was again down about 14 points from where it should be pre-boil. So my question is, can a bad crush really set you back 10-20 points on gravity? It seems like that is the only variable left that is messing things up. FYI I did not have any iodine to do the starch conversion test, wish I did.

 

[IslandLizard]

Sadly, yes, crush is a large factor in mash efficiency. If you saw whole kernels or barely cracked kernels, your mash is gonna tank. You could mash longer, that helps somewhat.

Many recipes are designed for (a lowish) 75% efficiency. If yours is less than that, something is wrong.

Sometimes milling twice helps a bit to get you maybe 10% extra gravity. If there's any small kernel grain, like wheat or rye included, they may drop through without much or any crush. Then you'll be asking too: "where is the wheat (or rye)?"

Mill your own is the best answer. "Corona" type mills can be had for around $25. About $100 for a Barley Crusher. If you can buy base malt by the sack at a decent price, you'll earn your mill back in a few years.

 

[Lefou]

Crush and mash pH are two big considerations.
There are times when I will turn a portion of my higher diastatic wheat malt to near flour. Adjusting your water with calcium salts can boost your efficiency, too, because it can improve starch-sugar conversion. Those two "tricks" have helped me gain a few extra points of efficiency with a simple batch sparge.
Furthermore, if you can do an all grain BIAB this way and treat your water to the desired SRM and style, your efficiency and conversion numbers should improve.

 

[dmtaylor]

Yes. Crush is the number one most important factor for those who care about efficiency.

 

[jalc6927]

The finer the crush the better chance at a stuck Mash or sparge. To prevent you can use a brew bag and mash normally

 

[Dirty-Thumb-Brewery]

We have first hand experience with this. Crush and temperature really helped us. We bought and motorized a 3 roller kegco mill to crush grain ourselves and got a lab calibrated thermometer. These 2 changes took us from around 70-73% to a consistent 80-82%!

 

[Horseflesh]

Simply double milling at the LHBS bumped me up 5%.

 

[jalc6927]

It helps efficiency but it does not change the gravity

You just get more out of your grain so you can conceivably use less, although on 5 gallon mash it doesn't make any real difference

 

[tootal]

About 4 beers ago we started losing efficiency. At first we thought we had done something wrong but then 2 beers ago I took a better look at the crush and I was seeing a lot of husk still holding the endosperm. I tightened the mill up about .005" and it looked really nice. Hulls were still whole but the endosperm was in 4 to 5 pieces. Our efficiency went right back up and we hit our numbers right on. We use a RIMS system so we can't mill too fine or it will stick. The pro's mill it to powder but then they have rakes that stir it to keep it from sticking, but their efficiency is amazing!

 

[Steveruch]

My efficiency goes up 15% when I mill at home as opposed to having my LHBS mill for me.

 

[SoCal-Doug]

Makes a hell of a difference in efficiency (the gravity is up to you and how you handle your efficiency).

I normally average 89 to 91 depending on the recipe. One batch a few months ago, I didn't pay attention at the LHBS as my son was helping me mill. Someone had adjusted one of the mills for BIAB or something (I think they were trying to make malt flour). When I mashed in I noticed the ultra fine grind and thought oh crap. Had my very first stuck mash from hell. During the entire mash recirculation I had to keep breaking up and stirring the concrete mass that would form in minutes. Not wanting to waste the batch, I kept trying. When it was all over and in the fermenter, the numbers came out at 96.5%. Here's the funny part... It was a Saison so of course we go for very fermentable and dry, and I was using 3711 (which can ferment distilled water and old gym shirts). The ABV was through the roof. I swear that stuff was flammable Learned my lesson, bought a mill.