Percent of fermentable sugars

Physics, chemistry and biology of brewing. The causes and the effects.

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brewmaster808
Light Lager Posts: 15
Joined: Wed Oct 06, 2004 6:14 pm
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Percent of fermentable sugars

If had two batches of wort both with a OG of 1.050. The differrences being one has a 76% fermable sugars and the other has 65% fermable sugars. If I use an yeast with a 70% attenuation, what would the outcome be and what is the formula I would use. I already know the general answer that the 76% will ferment out to a lower FG, but trying to show in formula why.

BillyBock
Imperial Stout Posts: 561
Joined: Sun Dec 31, 2000 11:37 am
Location: Ohio

In the Ballpark

To get you in the ballpark for your particular question, OG=1.050 w/ 76% attentuation, you would have 24% of the gravity remaining (100%-76%=24%). So then FG=1.050 * 0.24 = 1.012

It's very difficult to predict final gravity this way because there are so many variables that go into--amount of yeast pitched, health of the yeast, mashing program used, etc. So the above gives you an idea of where it might end up--it could be more, it could be less. The only way that I know for sure is to brew the recipe repeatedly so you know what to expect.

v/r
Bill

brewmaster808
Light Lager Posts: 15
Joined: Wed Oct 06, 2004 6:14 pm
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Deleted this message, have recieved email from White labs and confirmed there formula is same as Wyeast just done in another fashion, the -1 was meant as -1.0 and not as subtracting 1 point. My mistake. Here is the reply from White labs.
That is just the formula simplified, your probably doing it automatically by not using the 1 in your formula, for example instead of 1.060-1.010, your doing 60-10/60. But you can see how 1.060-1.010/1.060 won't work.
Last edited by brewmaster808 on Wed Jul 06, 2005 6:25 pm, edited 1 time in total.

brewmaster808
Light Lager Posts: 15
Joined: Wed Oct 06, 2004 6:14 pm
Contact:
Would this formula work, is it correct? Just pretend that there are no varibles. If I had two batches of wort both with a OG of 1.050. The differrences being one has a 76% fermable sugars and the other has 65% fermable sugars. If I use an yeast with a 70% attenuation

(100%-70%=30%). So then FG=1.050 * 0.30 = 1.015 (fermable sugars) (100% - 76% = 24%) .24 * 15 = 3.6 then 1.015 + .0036 = 1.0186 expected FG

(100%-70%=30%). So then FG=1.050 * 0.30 = 1.015 (fermable sugars) (100% - 65% = 35%) .35 * 15 = 5.25 then 1.015 + .00525 = 1.020