Krausen after secondary addition?

[Preturbed]

I'm currently fermenting 10 gallons of "milkshake IPA" designed to be sort of like a lemon creamsicle.

After a week of fermentation I zested six lemons, then removed the rind and seeds from four of them, added just enough overproof rum to sanitize, and made a tasty lemon slurry to give my beer, along with a big fat secondary hop addition. Before adding the stuff, I checked my gravity; the beer seemed pretty close to done.

Three days later I went to doctor another beer (a gose) and I found that the airlock in both fermenters was bubbling at a rate of about 1 per 5-10 seconds. I ventured a quick peek under the lid - krausen! There hadn't been any before. I guess what I'm asking is, did I really add enough sugars to the beer for those yeasties to go back into a krausen-forming stage? It didn't seem like much to me.

My original brix was 12.75
Brix upon secondary addition: 6.25
London Ale III yeast

 

[day_trippr]

Google says a lemon provides 1.5 grams of sugars, so you might have added around 10 grams of fermentables to your creation.
I rather doubt throwing 10 grams of sugar at a gazillion yeast would keep those single cell pyranha busy for long at all, never mind three days...

Cheers!

 

[RM-MN]

Along with the lemons you added a bunch of hops. Those hops form nucleation points for the CO2 dissolved in the beer to come out of solution and that is likely why you have krausen. At the end of fermentation there is a lot of CO2 dissolved in the beer and it isn't uncommon for that to keep bubbling the airlock for days or weeks as the excess is expelled.