Identifying the problem

[Safa]

I brewed a 6 gallon batch of APA two weeks ago, and split it into two 5 gallon carboys. Into these carboys, I split a smackpack of wyeast american ale II.

One carboy took off and went nuts almost immediately, whereas the other barely showed any indication of activity throughout the two week primary

When racking into a single carboy to dry hop, I took a little taste of each, along with a hydro reading of course.

The carboy that had lagged in performance tasted absolutely amazing. I swear it tasted better than the commercial APA I was drinking at the time. I took several sips of each and preferred the un-carbonated, warm beer!

Heres where it gets weird. The carboy that had been very active had a subtle off flavour to it. I cant put my finger on it for certain, but I've tasted it before with my homebrews, I just dont know whats causing it.

Everything about these two beers was the same! I have one explanation thats possible:

--- I pitched slightly different amounts of yeast into each carboy. BUT - tell me this -- why would the carboy that took off like a rocket be the one that tasted bad? Surely the one that suffered from presumed under-pitching would be the one with off flavours?

tl/dr - I have an off flavour, what the hell is causing it?

 

[Beernik]

Fermentation is exothermic. The one that had the more active fermentation fermented at a higher temperature because it generated more heat.

 

[freisste]

Fermentation is exothermic. The one that had the more active fermentation fermented at a higher temperature .

+1. You probably under pitched one slightly - not enough to cause glaring off flavors. The other went crazy and heated itself up. That caused it to go even faster in a vicious cycle.

Did you do anything to control temps? Bucket of water, etc?

 

[Safa]

They were side by side in a temperature controlled ferm chamber the whole time, the temp didn't go above 67 in two weeks.

 

[Beernik]

The chamber temp was 67F or the fermenter temp? If your probe is reading the chamber temp, the fermenter was warmer than 67F.