Mashing process question---when to pull the grain?

[DFWhomedistill]

I'm still a relatively new distiller and have done about 10 batches. I've been focusing lately on getting a proper fermentation and that has led me to taking a look at my mashing process. To frame my question, I've been making bourbons according to the "rules;" 51% corn, aged in new American oak, etc. After the mashing in process is complete I usually get 8-10% potential alcohol mash but I've not been able to get the fermentation process to run complete. After 5 days the fermentation seems complete but only has consumed about half the sugar at most so I'm getting about a 4-5% yield. I've done everything I can think of to get the fermentation to yield more; changing the acidity of the solution, different yeast types, aeration of the mash, etc.

What I think I'm doing wrong......I am fermenting with the grains still in the mash and straining them right before distillation. I've learned recently that whisky makers strain and lauter at the end of the mash process. Do bourbon makers do this? Would the presence of the grains in the mash keep the yeast from being able to consume a higher percentage of the sugar?

Any help would be appreciated before start another run.

[Pikey]

We need more than that. 51% Corn - what is the other 49% ? Now your "Mashing process" - Run us through it in detail - What temperatures are you raising to - times held - are you using malt or enzymes - if enzymes, which ? and what temperatures are you adding the enzymes or the malt ?

No I don't think your sugar is being masked by the corn.

[DFWhomedistill]

My mash bill is normally around 70% corn, 20% rye, and 10% 2- row barley. I use flaked corn and rye so I don't take the mash above 160. I add the barley at 150 degrees and let it simmer for an hour or so. The mash is normally really thick before the barley is added and thins out like it is supposed to. I do add couple ground up Beano pills too. I usually get readings with a refractometer that lead me to believe I have a 10% potential alcohol solution. I've done iodine tests and they show no starch.

[still_stirrin]

....I add the barley at 150 degrees and let it simmer for an hour or so.

Whatcha’ mean by “...let it simmer...”?

If you mean at a temperature just short of boiling, then you’ve successfully annihilated the enzymes in the mash. And I don’t think the Beano tabs will help you then.
ss

[RedwoodHillBilly]

If the other grains aren't malted, 10% 2-row is probably a bit low on DP to get full conversion. Briess 2-row has a DP of 140, so at 10% you would only have a total DP of 14. Rule of thumb is to have a total DP of 30 or greater.

[zapata]

The presence of the grains is not the problem. Bourbon is not only fermented on grain, it is distilled on grain too.
Honestly, I'm surprised you are passing the iodine test due to the low malt %. It is the first place I would start, try 55% corn 25% malt 20% rye.
Or keep your ratio and add enzymes.

[seamusm53]

My mash bill is normally around 70% corn, 20% rye, and 10% 2- row barley. I use flaked corn and rye so I don't take the mash above 160. I add the barley at 150 degrees and let it simmer for an hour or so. The mash is normally really thick before the barley is added and thins out like it is supposed to. I do add couple ground up Beano pills too. I usually get readings with a refractometer that lead me to believe I have a 10% potential alcohol solution. I've done iodine tests and they show no starch.

I think your yield is low because you cap temp at 160. While using flaked corn eliminates the issue of the corn husk physically preventing enzymes from reaching the enclosed starch, your corn starch remains 'inaccessible' because it takes a much higher temp for the starch to enter into solution - what is called gelatinization.

I have seen a falsely negative iodine reaction when the mash liquid is negative but if I add a drop of iodine to a cracked corn kernel squeezed between my fingers the reaction is obviously still positive.

But if I take the mash above 180 and hold it for 1-2 hrs, everything is iodine negative.

[Shine0n]

You could always boil the water and pour into the flaked maze, cover and let set for a couple hours insulated With some old blankets untiltime to add your malts.

Also up your malt to at least 20% or higher and you could use malted rye along with the malted barley to increase the dp, it may have a slightly different flavor with the rye being malted but it's going to make for a good drop

The enzymes of the malts will do its job so I think you could loose the extra expense of the beano tabs and buy an ale to pass the time while mashing. lol

I run a thumper so I just rack the clear beer into the boiler and mucky mess in the thumper and let her rip, if that's not the case for you then rack the good clear beer first then start squeezing, pressing the grains while you still the first batch.

Shine0n

[dukethebeagle120]

mash temp maybe.
getting some oyster shells in the mash
could be unfermentables

[Cu29er]

"...I am fermenting with the grains still in the mash and straining them right before distillation. ... whiskey makers strain and lauter at the end of the mash process....?"

Doing it the second way allows you to settle the liquid going into the still. Otherwise, a bunch of debris in the still even when strained, when it pukes will plug packing in the column creating a dangerous release of high pressure high temperature spray. It can spray yards out and cause second+ degree burns if you happen to be near it.

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