Yield vs mill setting vs Heads Fraction

[klattig]

Hi All, 

Early this year we started milling our grains more finely in an effort to improve yield.  We went from the 'standard' 0.038" we see used for malts a lot, to 0.024".  Sure enough, yields improved 10-20% (we have a lot of different mashbills, and some were affected more than others).

But, it seems like we are generating more heads than we used to.  This is hard to quantify, as it might just be that we're more attuned to the downsides of leaving more sharp notes in the spirit than we used to be.  But, it occurs to us that a finer grind might result in more cellulose getting ground up to the point that it is more fermentable than usual, resulting in more methanol.

Does anyone have thoughts/experience with the idea that a finer grind might produce a larger fraction of heads?

Thanks!

[captnKB]

a 20% increase in yield is a significant increase in alcohol in your wash. if your finishing ABV is high say over 14% the increase in heads production could be a result of over stressed or under pitched yeast, that did not occur before due to low sugar thus lower abv of the wash

[klattig]

captnKB, Yes, that makes sense.  But our OG is 1.070 or so; we never exceed 11%ABV after ferment.  I think we aren't stressing the yeast, but perhaps the finer grind provides more opportunities for methanol-producing activity...

[Silk City Distillers]

Think @captnKB nailed it, larger heads cut due to both higher yield and greater yeast stress.  Also keep in mind, higher starting gravities - in non-temperature controlled fermentations, can result in higher temperature spikes, which would impact heads volume.  What's the increase in product yield - the same 10-20%?

We saw roughly the same increase in product yield moving from a roller mill to a finer grind hammer mill.

Methanol generally results from high pectin fermentations, not cellulose - at least I'm not aware of why cellulose would easily be fermented into methanol.  There's lots of work being done on cellulosic fuel creation, most of it - methanol/ethanol - use highly complex processes to break down the cellulose.  Pectin contains the precursors to form methanol (methanol esters) - cellulose or hemicellulose doesn't.

[klattig]

Around the same time as we changed the mill size, we got a lot pickier about the timing of the heads cut, and stopped recycling any heads.  So the final product yield actually went down, but there were multiple factors involved (as usual, we changed too many things at once!).    Anyway, I think I've read that some methanol can come from one-off ferments of cellulose, but Silk City is right that the literature seems to support the idea that the vast majority comes from pectin.

This is off my original topic, but what ferment temperatures are folks generally using?  There's a wide range of answers on the web!  We do control ferment temperatures pretty tightly, but our target is typically 87F +/-2.  Any thoughts about that being too high, and producing more fusels,  etc?

[captnKB]

Ferment temp and process is going to depend highly on size of ferment, yeast type, ambient temp, beer gallon ratio.

With that said we pitch our 500gal wheated bourbon ferments at 68 and let them free rise to 88. Little to no temp control needed if done right. 

[Silk City Distillers]

We don’t like pushing grain ferments above 82f, we run actively cooled fermenters.

Does it matter?  Who knows.

 

[klattig]

I guess I'll run an experiment and find out!  We actively cool as well, and there's still a few weeks of relative cool here in AZ where I can keep my ferment as low as 80F...  If I don't ping back on this in a couple weeks, bump the thread & I'll post an update!

 

[Silk City Distillers]

Actually, we have a comparison case - we had the jacket ball valve fail on a ferment and it ran uncontrolled to about 93f, finished fermentation about a day faster.

Looking at the numbers, about 12-15% lower product yield on a proof gallon basis with a noticeably larger heads cut.

Distillate quality was nearly indistinguishable from a normal ferment, post cut.  Which was pretty surprising.  Had I not taken that larger heads/tails cut, it would have been pretty rough.

[klattig]

Interesting, and just what I'd expect!  Thanks for the feedback!