sudden high yeast activity

[Shandarr]

Hey all

I have a question about fermentation etc, I just brewed up my 3rd batch of home brew and followed the recipe to a tee with the exception of two things, first I added one whirlfloc tablet for clarity, and second I used an American ale 2 yeast in a smack pack. http://beerrecipes.org/showrecipe.php?recipeid=620 (link for the recipe there). Now after searching the forums out about this, it does not seem to be a problem, however I wanted to check and make sure, it is about 3 days into fermentation, in the first 24 hours you could see the airlock starting to bubble happily away and all was good, 48 hours in, it was still bubbling away as normal, when I checked it this morning, it seemed the fermentation was starting to slow down, the bubbling slowed and the layer of yeast on the top was starting to get smaller in thickness, now thinking to myself, ok maybe not all that much needed to be fermented and all was good, I come home 12 hours later from work and suddenly the yeast has bubbled up into the airlock and plugged it, didn't blow the airlock off or anything and I had left a good 8 inches give or take from the top of my 6 gallon glass carboy to allow for the yeast expansion, what could have caused this very sudden aggressive yeast activity? is it still good? the only other detail I can mention here is that there is about 6 inches of sediment at the bottom of the carboy from the blueberries used that I could not filter out at the time from the very start of fermentation.

After cleaning out the airlock and re-sanitizing it, it is seems to be slowly bubbling again immediately after replacing it, and the level of yeast foam has receeded a bit. Any thoughts on this?

Happy Brewing all

 

[flars]

First just a comment on the recipe. Berries probably should have been added at 185°. Seven days in the primary without SG readings seems short.
What was the temperature of your wort when the airlock plugged?

 

[DocScott]

Are you controlling your temp during fermentation? If not, did the temperature in your fermenting space increase recently?

 

[Shandarr]

temperature of the wort when the blueberries were added was at 180 and I am keeping the temperature controlled at 67 from the time the yeast was added. I also forgot to mention that I did let the wort settle a bit and siphoned off the wort from all the hops and blueberry gunk at the bottom of the stock pot, unlike the author of the recipe who let everything just ferment.

 

[flars]

If the temperrature of the wort was controlled at 67° you are probably okay. The sudden increase in krausen, I don't know. I've never had that happen with American Ale yeast though I don't use it over 64°.

 

[Shandarr]

I have been keeping an eye on things and have found that the Krausen has flooded the airlock a few more times this evening, but it does seem to be slowing down a little, but not much, after closer inspection of my glass carboy I have it fermenting in, I can see tiny bubbles coming up from the bottom of the carboy from what appears to be what is left of the blueberry pulp, it is probably that the yeast has finialy reached the bottom of the carboy and found the pulp and is very rich in natural sugars and is going nuts, along with a very slow dispersion rate of the krausen at the top, I tilted the carboy around a bit with the airlock on and seems to have lowered the level of it as well, along with lowering the temperature down to 64 as well to slow things down.

Hopefully it will still turn out.

 

[DocScott]

I doubt that your theory is the reason (as sugars and the yeast will disperse in the wort fairly evenly once fermentation kicks off) but I don't have a better cause. I suspected temp fluctuation but sounds like you have that under control. Anyway, I think you'll be good with this one.

In the future, I'd suggest fermenting your beer in primary, then transferring to you secondary with the blueberries there rather than adding them after the boil. The fermentation in primary is pretty vigorous as you can see and may drive off the flavor and aroma compounds of the fruit. Adding to secondary helps maintain them in the beer.