MY First Infection (I think)

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jacksonbrown

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Brewed a nut brown 7 weeks ago, bottled 3 weeks ago. I noticed a sourness when bottling that's still there now. I'm assuming it's an infection, or some wild yeast because of the taste and the fact that it attenuated 88%!
Oh well, first one in nearly three years of brewing. I'll take it.
 
Kind of like a flanders. It's not ridiculously strong, but it's noticeable. But if I had to choose I'd say vinegar.
 
Quote from a flavor chart I got somewhere.
SOUR-ACIDIC
CHARACTERISTICS: Another of the basic taste
sensations, sourness is perceived on the sides of the
tongue towards the back of the mouth. At higher levels it
can be felt in the throat. Generally in beer this is
perceived as a sour aroma and a tartness or vinegarlike
aroma. Sourness from bacterial contamination can also
be perceived as spoilage or putrefaction.
CHEMISTRY: Caused by lactobacillus, pediococcus,
acetobacter and some yeast strains.
HIGH CONTENT DUE TO PROCESS: Poor sanitation;
poor yeast strain; excessive amounts of citric or ascorbic
acid; high fermentation temperatures; excessive acid rest;
mashing too long; storage at warm temperatures;
scratched plastic fermenter.
LOW CONTENT DUE TO PROCESS: Good sanitation;
cool fermentation temperatures; cool beer storage;
mashing for less than two hours; glass carboy or stainless
steel fermenters.
Hope this helps you prevent further problems.
 
Another quote from same flavor chart.
ACETALDEHYDE
CHARACTERISTICS: Acetaldehyde has the flavor and
aroma of green apples. It can also taste and smell
acetic/cidery.
CHEMISTRY: Formed as a precursor to alcohol by the
yeast, or as a product of the oxidation of alcohol to acetic
acid.
CAUSES: Acetaldehyde from yeast metabolism as a step
in the production of alcohol from glucose has a crisp
green apple flavor. If produced from the oxidation of
alcohol to acetic acid, whether by oxidation or by
acetobacter, this flavor will be more vinegary and less
pleasant.
PROCESS: As a product of yeast metabolism, it can be
caused by the strain itself or by premature termination of
the yeast's fermentation. The reaction from glucose to
alcohol may be stopped at the acetaldehyde stage by
factors such as oxygen depletion, premature flocculation,
etc. It may also be produced by contamination by acetic
acid bacteria.
REMOVAL: Use a good yeast strain that will attenuate
the wort properly. Oxygenate the wort at yeast-pitching
time. DO NOT splash or oxygenate the wort when
racking or bottling. Long lagering periods will also reduce
acetaldehyde.
 
I have a feeling it was the yeast (although I did use US-05, which has been great to me) because I've been brewing a lot lately and no other problems. Could be something got in the carboy after sanitation and before pitching, but it's doubtful. Oh well, like I said, one (3 gal) batch in three years I can handle.
 
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