Temp rise indicative of some fermentation?

[donshizzles]

So I brewed up a 5.75 gallon batch of milk stout today. I've gone over my numbers a few times and am coming up with a 90% brewhouse efficiency, effectively hitting better than my estimated numbers (I've usually been in the 82-87% range).

I pitched US-05 into 71 degree F wort after a 60 sec shot of O2 with a 0.5 micron diffusion stone. I'm using a blow-off tube sitting in a jar of Starsan solution and have seen no bubble activity after 8 hours. I'm not concerned at all as I know activity usually takes upwards of 24-72 hours to show signs of life, if at all. The temp after a few hours in the fermenter dipped down to 67 degrees (constant temp probe sitting in the wort) and held there for a few hours (room temp is constant). Now it has risen back up to 70 degrees F.......is this a possible indication of the beginnings of fermentation? Still no bubbles in the Starsan jar but I figure this thermal rise is a good indication the yeasties are happy so far

Thoughts?

 

[C-Rider]

I would think so if the room temp is not changing.

 

[RM-MN]

Yes. Fermentation is exothermic so you should expect a temperature rise as the yeast get started. The activity of the yeast increases with higher temperatures too. When I start fermenting at 59 ambient the fermenter will only come up about 1 degree. At 62 ambient, it will rise about 2 degrees. Higher temperatures will lead to a faster rate of fermentation and the temperature rise will be greater.

 

[donshizzles]

I'm using a Northern Brewer plastic bucket as the primary. Whats the thoughts on leaving it in there for up to 4 weeks before racking to secondary? Any concerns that long in plastic?

 

[RM-MN]

Only 4 weeks? Pfft! Not a problem. I've left a beer for 9 weeks and the only thing I noticed different was that it didn't take much time in the bottle to be ready to drink.

Are you adding anything that would make a secondary a good idea? If not, just let it stay in the primary.

 

[donshizzles]

No, not adding anything to it for justifying a secondary. It seems there are equal arguments for and against racking to secondary. I've just always used a secondary fermentation as I've read leaving the beer on the primary trub for an extended length of time can contribute to off flavors from autolysis.