Advice sought: Puzzling difference in fermentation between 2 identical carboys

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tunoffun

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This is actually a wine related question, peach wine in particular.

We started 2 5 gal buckets of peach wine recently. The peaches were all hand-picked and consistent in quality. Added meta and 1/2 the sugar to start, then waited 24 hours to pitch (same yeast strain, same production date). The only diference between the two is that the #1 bucket ended up with alot more pulp in it than the #2.

After the gravity dropped to ~1.20 we transferred over to carboys and added another 1/4 of the total sugar. To this point, both containers had shown about the same vigor in fermentation. Bucket #1 may have been exposed to air a bit more than #2 during transfer. We weren't overly cautious with either as we were transferring during active fermentation.

Once in the carboys the situation chnaged. Both carboys took about the same time to show signs of fermentation, but once that happened, #1 took off with a rapid, violent fermentation, producing a voluminous head of pure white froth, while #2 had virtually no head at all... just a thin cap of what pulp did make it through, with significantly less CO2 production. #1 was literally churning, while if it weren't for the bubbling airlock, you might mistake #2 for having stopped.

Within a couple days #1 had slowed to a crawl, while #2 continued on its slow, but steady, pace. After about a week, gravity was checked and both were down to ~ 1.000. So we added the last 1/4 of sugar directly to the carboys and stir it in. This is where things get even more interesting.

Adding sugar to #1 is uneventful. But as soon as we started pouring into #2, it errupted, overflowing like a can of soda shaken up on a hot summer day. So if I'm not mistaken, #2 is, for some reason, trapping alot more CO2 in solution than #1.

I guess my questions are... does that sound reasonable? And if so, do you think it explains the difference in fermentation vigor between carboys? I'm thinking that perhaps the high ppm of dissolved CO2 in #2 might have been inhibiting yeast activity?

Another question would be why the difference in CO2 content in the first place. The only significant difference I can think of would be the pulp content. Would this explain one allowing CO2 to gas off where the other retains it?

Anything I haven't mentioned that I may have overlooked?
 
There may be something to the difference in amount of pulp, but I don't know what it is. K-meta isn't always a surefire proposition- perhaps one of the carboys got some wild yeast in there and those are contributing something. That seems unlikely, though, the pitched yeast should totally outcompete them. Temperature could also be an issue- even buckets sitting right next to each other could be different temperatures. That might explain the extra CO2 in the one, but I have no idea. In my experience though, ferments can look different each time and still produce the same product. Weird.
 
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