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Jun 08, 2022 View:

Low efficiency

We are getting low efficiency on our mashes, hoping to get some eyes on our mashing regime to see if anyone has any input to up our numbers. 4X 300 gallon mashes

250 gal water, 350# corn, 220# malted wheat, 55# malt

add corn to water, ph to 5.4, add 20ml Bioglucanse and 200ml Hitempase from BSG

heat to 195 and hold for 30 min

cool to 140, add wheat and malt, add 20ml Bioglucanase and 200ml Amylo300 from BSG and rest 30 min

Cool and pitch yeast. 

I calculated this to be 46.13 bushels and we only yielded 124.3 proof gallons, or 2.69 PG per bushel. 


Any thoughts on getting our PG per bushel number up is greatly appreciated.  We are seeing low yields across many different mashes mashing this way which makes me think I'm doing something wrong in my mashing, or its another variable such as weak enzyme or corn that isn't milled finely enough. Also of note, extended rest times don't affect starting gravity. 


Malt and malted wheat are going to have a lower PG per bushel than corn. Was this field corn you used or something else like flakes?

Also that mash seems thick for on-grain, at a 22 beer gallons (liquid volume/bushels) -- was this lautered? We run a 30 gallon beer here and usually get 4 to 4.4 PGs per bushel. 


Field corn, on grain ferment and distillation. Original was 16 plato and finished dry


My best guess is it is either too thick or not coarsely ground enough, either or potentially both leading too poor conversion. We hit north of 16 plato with 75% of the grain you used. Our process is almost identical to yours, but we are doing our malt rest around 145 instead of 140, but I don't think that would make that big of a difference in conversion.

It sounds counter-intuitive, but I'd try going thinner and see if your yield goes up, seems a lot of people on here struggle with yield with the thick mashes.


We struggled with similar low yields using fine cracked corn.  Optimizing fine cracked corn required 90-120 minutes at temp, thickness was a major impediment to full gelatinization.  We could run iodine starch tests forever it seemed with the fine crack.

Tom is right, go thinner, and push your hold temperatures longer.  16 plato starting seems very low, would have expected 19-20 with that much grain.  The fact that you are finishing dry points to getting complete fermentation of the starch you are extracting (no residual dextrin, etc - wouldn't expect that with glucoamylase).  So that points to starch extraction from the maize.

Hammer milling the grain ourselves pushed yields up 20% overnight.


4.2 to 4.8 pg per bushel consistent average on a 750 gallon cook. 5 to 6 hour total cook and cool. Cook at 18.5 gallon beer. Pitch at 15.5 to 17 brix pH 5.8 to 6.  End up with a 23 gallon beer at set. 


Appreciate the replies.  We don't have a hammer mill yet, and the corn we use is pretty roughly cracked on a roller mill, trying to get our supplier to mill it finder for us. I have played with 30 and 60 minutes for both rests and I see a bump of 0.5 plato max with the extended rest

Trying my sacc rest at 145 crossed my mind as well, so will be trying that on todays first mash using the same mash bill to limit to a single variable, for the second mash I will thin it to see how it reacts. 


Push longer on coarse crack try 2 hours and move backwards from there, moving from 140 to 145 isn't going to solve this.



I'll give that a go right now and see where we end up, thanks


We use coarsely ground corn and rye here and get great conversion with 45 minute temp rests. For the most part, our ratios match up. Though it is tough to say when we're not using the same brand of enzymes. My one thought is that you may want to contact your enzyme supplier about how to maximize their efficiency. We use a high temp alpha at 2ml per gallon / final mash volume, added after the first 25% of grain is added. It works like a charm in the 170-190F range. We then pitch our gluco amylase as we start to fill the fermenter, right before we pitch our yeast. Another question, which has resulted in lower yields for some folks: how low are you collecting your into stripping run? 


I too was wondering about our enzymes and will reach out. I collect low wines down to 5 abv


Just ran this mash with extended times, 2 hour cook and 1 hour sac rest with no changes. Chalking it up to too coarse of a mill and or weak enzymes 


Post a photo of your corn.  You have more than enough malt to convert without the additional enzyme.  The enzyme is gravy on top.  Keep in mind the glucoamylase will remain active throughout fermentation, that's like sprinkles on your gravy.


Been going back and forth with supplier on the milling, they only have a roller mill but are working with me on getting it crushed finer. This last batch came in particularly horribly milled, a bit of whole kernels even. Bummer because I like their products, but looking at alternative suppliers or more than likely a hammer mill for our shop. 



this person here is selling one.


Also Tractor Supply sells a small one with different size screens if you just want to experiment.  450 pounds per hour, so you'll be there for a while...





Reply:7 minutes ago, Windy City said:
Reply:On 10/7/2020 at 8:32 AM, Windy City said:
Reply:On 10/6/2020 at 10:31 AM, kleclerc77 said:

try holding high cook temp longer, also like others said use a little more water. Hydrolysis consumes water. 

Reply:On 10/21/2020 at 10:23 AM, Tradesman Spirits said:

So mashed two batches of bourbon today, each 350# corn, 110# unmalted wheat, 82.5# peated malt. Same mash regime as the original post, but the first one at 30 min rest at 195, and the second at two hour rest at 195, both 15 plato original gravity. Hammer milled all grain to flour, no clumping or any issues, ran perfectly smooth. Thoughts?  

Reply:3 hours ago, Brewstilla said:
Reply:2 hours ago, Bier Distillery said: