Math help.

[bluemoose]

If I brew a beer that typically has an OG of 1.060, but brew it with sap put through a RO machine with an original gravity of 1.060, what kind of alcohol content am I looking at? I have about 20 gallons of mash and sparge water at that gravity.


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[nukebrewer]

So to get the numbers straight:

OG of beer with real water = 1.060
SG of mash and sparge sap = 1.060

And you're wondering what the OG of the beer will be?

You'd need to provide the grain bill (or at least total grain weight) and the yeast you are planning on using to do the appropriate calcs.

Or you could just do what I do; brew it and see what happens. One concern I would have though, is that the sap wouldn't have the proper mineral content for what you're trying to brew.

 

[bluemoose]

11lbs of grain. MO, Vienna Munich and crystal. S-05 for yeast. Style of original beer is pale ale.


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[ianw58]

"but brew it with sap put through a RO machine "

So...basically nice clean, pure water with nearly everything in the sap removed by the RO membrane...

The sap, by itself, BEFORE the RO process, is a very dilute solution of sugar. Typically, the sugar content of sap is anywhere from 1 to 5%. That's why it takes so much sap to produce a small volume of syrup. You can pretty well assume a few points of sugar per gallon of sap.

 

[knyland]

Alright lets assume you are getting 36 points per pound on your grain that's 396 points/ 5 gallons = 1.079.2 assuming you get 75% efficiency that brings your OG to 1.059.4 if your yeast only consumes 75% of the sugars that will bring your FG down to 1.014.85. Rounding all the numbers and calculating for FG that brings your beer to about 5.9% ABV


Hope this helps if my math is correct....

 

[bluemoose]

I am expecting closer to 12%, I think. I must be explaining things wrong. I'm just going to brew it.

 

[satph]

By RO sap, I assume you mean that you are collecting what would usually be the waste from the RO, concentrating the sugar in the sap to create a liquid with an OG of 1.06. 1.06 is equivalent to 14.7% brix according to this calculator.

We can assume that sap is just water and sugar. If you had no boil-off, the OG of your beer would be the sum of the two, or 1.12.

A gallon of water weights 8.33 lbs. So a gallon of 14.7% sap would have 1.22 lbs of sugar. I'm not sure how to account for some of it sticking to your grains or equipment along the way. But if you use 6 gallons of water, that's the equivalent of 7.3lbs of sugar. A 5 gallon batch with 11lbs of grain at 75% efficiency in beer smith comes to 1.06, if I add 7.3lbs of sugar, I get 1.127. I would expect double-digit ABV.

 

[bluemoose]

That was my thinking. I decided to sparge with water. By doing so I will reduce the ABV to somewhere in the 9% range and be able to make another batch.

 

[bluemoose]

Finished. Batch one was 1.085 OG. Batch two was 1.11. I have about 10 gallons of high test sap left.


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