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Calculating alcohol from grain


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I don't know about TTB tables, but here is a table ripped from The Alcohol Textbook 4th Edtion by K.A. Jacque, T.P. Lyons, and D.R. Kelsall. Published 2003. ISBN1-897676-13-1

Table 2. Typical alcohol yields from various cereals.

Cereal Yield (US Gallons Alcohol/Bushel)

Fine Grind Corn1 (3/16 inch) ---------- 2.85

Coarse Grind Corn (5/16 inch)---------2.65

Milo ------------------------------------------2.60

Barley ---------------------------------------2.50

Rye ----------------------------------------- 2.40

Note that a distiller’s bushel is always a measure of weight. It is always 56 lbs., regardless of the type of grain.

1 Laboratory data using Rhizozyme™ as glucoamylase source.

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Most recipes I have read call for 3 lbs grain per gallon of water. An 8% yield will give approximately 1 750 ml bottle of 80 Proof per gallon of wash. Reversing the math on this gives 1.48 gallons of 100% per bushel. Close to what was posted above, if the above is proof gallons.

Is 8% realistic without adjuncts?

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The standard for the distilling industry for whiskey contacts is 5 proof gallons per bushel.

The 2.85 gallon per bushel is wine gallons used by the fuel plants and that's on dry alcohol but it would never make beverage grade.

High quality GNS we make I use 1.7 wg per bushel and sometimes ( often ) that's pushing the yield and the rest goes for vinegar grade alcohol. Also distillers and beverage alcohol is almost always wet ( not 200 proof )

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Please forgive my stupidity.

This is all very confusing.

A bushel is 50, 53 or 56 lbs, depending what type of grain, 56 for corn and Rye.

3lbs / gallon, from what I can find as being a pretty standard ratio in recipes, would mean approximately an 18.7 gallon wash.

Are you saying this will give 5 gallons of 100 proof?

That would have to be close to 13.5% after fermentation.

In my home brewing experience, I can't get above 8% without adding sugars.

What am I missing?

Thank you

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This is actually pretty simple. The table referenced in the first post refers to the number of wine gallons of total alcohol produced from a bushel of grain. That is the number of gallons of 200 proof alcohol (heads, hearts, and tails, everything) that can be expected from 56 lbs. of a particular grain. Let's take corn for example:

According to the USDA, dried yellow feed corn has a carbohydrate content of 74.26%, but 7.3% of which is fiber, and thus won't be fermentable to alcohol. That leaves a starch content that can be fermented of 66.96%. On a bushel of grain, 56 lbs. , this works out to 37.5 lbs. of fermentables.

If all the available starch were converted to sugars, that leaves us 37.5 lbs. of sugar. Theoretical conversion of sugar to ethanol is 51.1% by weight. That means 1 lb. of sugar yields 0.511 lbs. of ethanol. Using this, our 37.5 lbs. of sugar has now turned into 19.16 lbs of pure ethanol.

Pure ethanol has a density of 6.58 lbs./gal. Our 19.16 lbs. of ethanol will yield 2.91 gallons of 200 proof ethanol. That is pretty close to the published 2.85 gallons that was predicted from the table. However, this math doesn't take into account the inability to convert all of the starch to sugar, or the inefficiency of fermentation.

This same math could be used to calculate the theoretical maximum alcohol yield for any grain. The only piece of information to know at the start is the mass percent of carbohydrates that can be converted to sugar.

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  • 3 years later...

Does anyone have Dwrich's USDA reference to the %fermentables of small grains beyond corn?  I'm interested in growing some that work in my area and am curious which ones may make the best sense.  Corn is pretty easy.  Wheat may be more of a challenge due to lodging and smut.  But some others if there were tables would be interesting to play with.  I'm chewing on some heirlooms to try. 

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