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Old 04-28-2013, 04:00 PM   #1
buble
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Do acids from a mixed bacteria and yeast ferment affect the specific gravity reading? I am having a hard time figuring out if I can accurately measure alcohol in a brew that has all these extra things like bacteria and acids.

 
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Old 04-28-2013, 11:31 PM   #2
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Originally Posted by buble View Post
Do acids from a mixed bacteria and yeast ferment affect the specific gravity reading? I am having a hard time figuring out if I can accurately measure alcohol in a brew that has all these extra things like bacteria and acids.
No, yeast and bacteria (or other things suspended in the wine) don't affect the SG readings.
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Old 04-29-2013, 04:59 PM   #3
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Originally Posted by buble View Post
Do acids from a mixed bacteria and yeast ferment affect the specific gravity reading? I am having a hard time figuring out if I can accurately measure alcohol in a brew that has all these extra things like bacteria and acids.
In theory, yes - the acid (and anything else dissolved for that matter) will affect the reading. In practice, the amount of acid is so low relative to water/sugar/alcohol that your hydrometer isn't calibrated to detect the subtle differences.

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Old 04-29-2013, 11:08 PM   #4
buble
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even if the ph is around 3-3.5? would that still be low relative to the water/sugar/alcohol?

 
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Old 04-30-2013, 11:50 AM   #5
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Originally Posted by buble View Post
even if the ph is around 3-3.5? would that still be low relative to the water/sugar/alcohol?
Yes, even at pH 3 it shouldn't make much difference with the acids that would be present. Also remember that to determine alcohol you need to know both the OG and FG. Any acid that is in solution to start isn't going anywhere during fermentation so the gravity contribution can be ignored (it is there in both readings you take), and any acid that is created as a byproduct of fermentation is closer in density to the starting sugar than ethanol so can also pretty much be ignored.

 
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