Homework done but still low mash efficiency: Bad grain crush?

[brew2015]

Hi everyone. It's the first time I post here but definitely not the first time I use the forum to get useful hints.

I have just finished my fourth brew last week. Despite all the changes I incorporated in my process (described below), I am still hitting low mash efficiency values (~65%). I suspect it's because of improper crush, but I wanted to hear the opinion of the specialists.

(that 65% was calculated from the maximum sugar points that the grains could generate + volume and gravity after boil - gravity measured both with refractometer and hydrometer).

All the 4 times I bought the grains in the same shop and milled it there. In the last 2 brews, I passed the grains twice in the mill. In my last recipe, I kept some grain to take a closer look. I tried to separate it by grain size and noticed that:

- 9% of the grains in weight were totally uncrushed
- 26% were fine or very fine particles
- 65% was a mix of husks and crushed grain, from which I took a picture and attached here.



I noticed some grains are broken, but still inside the husk, which is not good. Is that a sign of coarse crush? Could you share some photos of how a proper crush would look like? I would really appreciate some guidance from you guys!

Thanks in advance!

Details of equipment/process:
- All grain brewing, usually 2gallon batches
- Recipes made so far: IPA, American Pale Ale, Irish red Ale, American Stout
- Mash tun: 5gallon rubbermaid cooler with a circular false bottom.
- Single temperature rest mash (64-69oC)
- Batch sparging
- Mash tun loss is very small (~300ml)
- No problems with stuck sparge so far

Some of the improvements I found in the forum and implemented after my 1st low efficiency mash:

- I'm putting hot water in the cooler before mash to warm it.
- I installed a thermal insulation at the lid to avoid heat loss (it was getting hot in the first brews)
- During my mash, every 15 minutes I open the cooler, stir, measure the temperature and collect some wort to make iodine test.
- I only stop mashing when iodine test is negative
- I am batch sparging, using a sparge temperature that takes the mixture to ~72 oC.
- In my last brew, my mash started at 69oC and finished at 60oC after 1h45 (I lose some degrees every time I open and stir). I mashed for a longer time to guarantee I was not losing sugars due to lack of conversion.

 

[Beernik]

Low efficiency is annoying but it's not the end of the world. On a 5 gallon batch, the grain difference between a 66% and an 80% efficiency for a 1.050 wort is about 1.8lbs. Thats a grain cost of less than $3.

I understand the frustration though. I never got better than 66% with my LBHS's crush. And their crush looks a lot like your picture. I think LBHS don't want to set their crush too fine because then everyone will complain about stuck mashes.

On the right is what I use in my BIAB. It might be too fine for a more traditional mash setup.

 

[Qhrumphf]

Crush certainly looks coarse to me.

I am 100% behind each and every homebrew who brews all-grain buying their own mill. Not only is low efficiency a problem with store crushes, but inconsistent crushes too. If the grain mill gap is too wide, doesn't matter how many times you run it through, you won't get a good crush. And if sometimes it's less than others, consistency goes out the window. Unless they'll let you bring in a set of feeler gauges and adjust yourself to the same point every time, there's no way around it.

Plus there's the lack of shelf life from crushed grain. Which prohibits buying in bulk (or reduces beer quality if you do buy in bulk anyway). And the savings from buying your grain in bulk uncrushed and then crushing yourself will more than pay for the mill very quickly.

 

[brew2015]

Thanks for the replies, guys. In my last brew I changed the place where I buy my malt. Grain crush looked better, as you can see in the photo below (it's 50% wheat malt, 50% pilsner malt):



However, when I brewed (following the same guidelines I posted before), I got the same ~65% mash efficiency.

Then I decided to take a look at the spent grain:



There were several grains that were broken in the half but still with the kernel intact inside. Do you also see that?



I dropped some iodine over them and the color indicated that it was starch, or at least a good amount of it. Could that be unssoluble starch? I read in some threads about the presence of that, but I also read that most modern malts are designed in order to give a high amount (~80%) of soluble starches.



I took some of those broken grains with intact kernels, added water again and boiled for about 5 minutes. To my surprise, the kernels were still there, even after 5' at 100oC. So maybe that's indeed inssoluble starch + proteins...

Anyway, after all that I decided to buy a small 2 roll mill. When I receive it, I will make some experiments to adjust the gap and I will also try to condition the malt to facilitate husk separation without shredding. I will keep you posted.

Thanks!

 

[oujens]

I think with wheat malt the grains are smaller so they won't crush the same as a two row or Pilsner. You Would need a tighter gap. In addition, wheat has a longer conversion time, so it's possible you did not reach full conversion before you drained the tun. I recently made the same mistake. I have struggled with efficiency issues on other beers and finally invested in a cereal killer. My first batch hit 82% efficiency when I usually hit between 65% and 75% with LHBS crush.

Are you measuring mash pH as well? Or atleast using a calculator?

 

[RM-MN]

Low efficiency is annoying but it's not the end of the world. On a 5 gallon batch, the grain difference between a 66% and an 80% efficiency for a 1.050 wort is about 1.8lbs. Thats a grain cost of less than $3.

Not a big cost but at 10 batches you would have paid for a Corona style mill and had control of the milling quality.

I think with wheat malt the grains are smaller so they won't crush the same as a two row or Pilsner. You Would need a tighter gap. In addition, wheat has a longer conversion time, so it's possible you did not reach full conversion before you drained the tun.

Wheat is definitely smaller than barley and harder too so you need to set the mill tighter to accommodate that. If the wheat is milled as it should be it converts just as fast as barley but most of the time it won't be crushed as well so a longer mash time allows the wheat to convert too.

 

[eric19312]

Crush is part of the equation and may be huge issue for BIAB brewers but everytime efficiency gets raised it seems to be number one suspect. The right crush depends a lot on your system and how you brew. I like that you are trying different crush from different retailers and agree that once you find what works best for you having your own mill and crushing it the same way every time will be key to consistent efficiency. IMO consistent efficiency is much more important than high efficiency.

You mentioned the following things you have tried:
- I'm putting hot water in the cooler before mash to warm it.
[were you having difficulty hitting target mash temperature? brewing software can compensate for heat loss to warm the mash tun]

- I installed a thermal insulation at the lid to avoid heat loss (it was getting hot in the first brews)
[good]

- During my mash, every 15 minutes I open the cooler, stir, measure the temperature and collect some wort to make iodine test.
[seems excessive. one stir mid way through should be enough. the heat loss is you were preventing with the insulation is nothing compared to opening and stirring]

- I only stop mashing when iodine test is negative
[eh I never had luck with iodine testing but like your pictures. If you have a refractometer you might consider watching the increase in sugars in the mash liquor, I've never done that but am considering]

- I am batch sparging, using a sparge temperature that takes the mixture to ~72 oC.
[Sounds good. When I batched sparged I got better by following Yooper's advice to really stir in that sparge water agressively. "Stir it like it owes you money" I think she says. I'd add don't worry too much about hot side airation. Stir well!]

- In my last brew, my mash started at 69oC and finished at 60oC after 1h45 (I lose some degrees every time I open and stir). I mashed for a longer time to guarantee I was not losing sugars due to lack of conversion. [that is a really big temp loss and a really long mash. I am much more worried about those factors then about your crush]

You did not mention a few other issues that can have impact on mash.
+ Mash thickness. A thinner mash increases conversion. A balanced mash with equal parts runnings delivered from mash and sparge is about optimal for lauter efficiency.
+ Water chemistry. Probably not the issue unless you have some really odd water but might be worth thinking about.
+ Lauter rate. I know Denny and others who advocate Batch sparging say rate doesn't matter but in my system it did/does. Slower liquor collection improved my efficiency.

I also think it might just be harder to get high efficiency at 2gal batch size. Maybe all the things that work well at 5-10-20 gallon batch size are wrong things for 2 gallon. Figuring it out is part of the hobby...have fun!

 

[TheMadKing]

I found that a 90 monute mash followed by some serious bag squeezing raised my efficiency by almost 10%, I usually hit in the mid-70% range now and am content with that.

I fiddled with the crush a whatnot too, and found the squeezing and long mash to help the most.

 

[stpug]

To determine your mash efficiency (i.e. if your crush and/or conversion is problematic) we would need to know:
-Complete grainbill
-Precise preboil gravity
-Precise preboil volume

Once you know your mash efficiency you can determine ways to improve it or look down the line at your brewhouse efficiency, which will always be less.

 

[brew2015]

Thanks for all the replies! Answering the questions:

- I just received my roll mill yesterday, so in my next batch I will be able to adjust the gap accordingly. I will probably waste some grains to fine tune the gap, but once that's done all the subsequent batches should be fine (I hope!).

- I measured the pH in my last brew using a pH-meter I had just calibrated. After 20 min of mash, pH was 5.1 and kept that level until 40 min at least. That's probably lower than the recommended value of ~5.3 I have read in forums, but I'm not sure that's the issue here because I think my problem is related to dissolving the starches, not converting them (investigations continue).

- Reaching the mash temperature is not a problem; in fact, using the recommended temperatures from BS I am reaching the target temperature with less tha 0,5oC of difference. The problem is to keep it (see bullet below)

- I will take the suggestion from eric and reduce the frequency of stirring to probably only 1. Thinking about that, it's likely that the temperature drop I notice is due to the fact that the wort has to "re-heat" the air of the headspace of the mash tun every time I open it. I might also try to stick some styrofoam plaques under the lid to reduce the headspace and therefore wort heat loss.

Considering calculations: I am calculating the efficiency based on the post-boil volume and gravity. The reason is that I can measure those two values with the wort around 20oC, whereas in the pre-boil I can only take at >70oC (or I would have to chill out the wort just to heat again to boil), which causes variations on both gravity and volume. Just to double check, I measure gravity with a refractometer and a hidrometer, having always close results (0,002 error max). For volume: I measure the wort height in the kettle, and calculate volume from that.

However, theoretically the calculations should lead to the same value, since the gravity points are kept after boil. I have some gravity points lost in my mash tun deadspace, but that should be very small (300ml of dead space).

Finally, if my calculated mash efficiency is not high, it's at least consistent, so maybe now using my own roll mill I will get the best of both worlds.

Thanks again everyone, I will keep you posted.

 

[b1v1r]

With my LHBS, I had the opposite issue. They tend to cater to BIAB and crush too fine for my equipment. I get great efficiency, but at the expense of a very slow mash recirculation and occasional stuck sparge. I borrowed a mill from a friend, it was not very consistent, but I got better mash/sparge results with a coarser mill setting (though less efficient). I have since gotten my own mill and am playing with grain conditioned milling. With this type milling I can set the mill gap finer for better efficiency and not have it destroy my hulls. Now, I have not yet had a chance to use this in a mash, but I think that the results will do wonders.

You can see some pics of this here: https://www.homebrewtalk.com/showpost.php?p=7117953&postcount=621

Later I will post my results on my system with this (have not had the time yet). Thought I'd mention it, though, as it seems like it can give the best of both worlds (more efficiency and less stuck sparges). You will need your own mill, though.

 

[brew2015]

Hi everyone. Just to update: on my last brew session I finally had the chance to use my roll mill crusher. And the results were pretty good!

Just out of curiosity, I took a photo of the brew shop mill gap and confirmed that it's probably too high (maybe close to 2mm). See below:



Before start crushing, I conditioned the malt with about 2% of its weight in water. I sprayed it over the grains and let absorb for about 10 minutes.

I varied the roll gap between 0,90 and 0,95 mm. When I tried 0,95mm, I had the impression that there were too many grains coming out intact. With 0,90mm, There seemed to be too much flour (although I did not notice any complications due to that afterwards):



I guess the best alternatives would be something between 0,90 and 0,95mm (hard to have that precision) or try to use a little bit more water in the conditioning of the grains.

Below is a photo of the grains just after crushing. The kernels were very well crushed (maybe too much?) and the husks were well preserved. That was confirmed by the photo and also later, when I dried the spent grain and saw a lot of intact husks.



I used a low mash thickness (2,7 L/kg) and opened the mash tun only once to stir. I also reduced a lot the headspace of the tun (thus reducing the heat loss to air). In 30 minutes, the heat loss was only 0,2oC, so I guess the cooling I was noticing before was indeed due to headspace and too frequent opening.

My mash efficiency, which used to be ~64%, was now 74%! I guess in the next brew, having already adjusted the mill, I will be able to get close to 80%, which is awesome.


The only complication I had this time was during filtration. I had no stuck spare, but when I increased the drain speed, several small grain parts came out. I had then to drain very slowly.

Interestingly, the trub loss was lower than average. Considering that the husks are preserved and should be filtrating well, I guess that those small particles are probably passing under the false bottom (it's a domed false bottom). I am trying to find a way to better attach it to the bottom of the mash tun, but had no good ideas so far. If anyone can share any ideas, it would be appreciated!


Anyway, after all the experimentation, I should recommend to anyone to buy his/her own roll mill!

Thanks for all the comments so far. :rockin:

 

[dwhite60]

0.90mm to 0.95mm is only 0.002 inch. Should not have made that much difference. Las time I brewed I conditioned my grain for the first time and ended up with a 0.65mm gap. Had a great crush.

It's just what worked for me. I think you can go closer on your gap.

All the Best,
D. White

 

[StandingZ]

I believe that I'm having a similar problem with Grain Crush, would it be recommended to run the grains through the mill twice? Or would that ruin the grain?