Carbonated Yeast Starter?

[Spartan1979]

I've been homebrewing for 30 years and never had this happen before.

I smacked a pack of Wyeast 2633 Saturday night. It didn't swell much and I made a starter with it on Sunday and threw it on the stir plate. Tuesday morning I put in in the fridge at 38 degrees after putting a rubber band around the tin foil. Yesterday I went to pitch it into the Rauchbier I brewed. AS I was pouring off the extra liquid, I noticed that it was foaming. I tasted a sample and it was carbonated!

The starter didn't really make all that much yeast and I didn't trust it so I pitched some W34/70 instead.

I've never tasted my starters before but I would think the stir plate would knock out most of the carbonation and it wouldn't still be fermenting after 36 hours, especially at 38 degrees.

Edit - I forgot to mention that the yeast was about 4 months old when I made the starter.

 

[3 Dawg Night]

Did it taste sour at all, like there might be something other than yeast in there?

 

[Spartan1979]

Did it taste sour at all, like there might be something other than yeast in there?

No, it tasted okay, although it was the first time I've ever tasted one of my starters. Even sitting in the fridge at 38, it had a small amount of foam on top like it was still fermenting.

 

[marc1]

Maybe it was in bad shape and took longer to wake up and get going, and was still fermenting when you put it in the fridge.

 

[McMullan]

It's possible this starter had only just started fermenting when it was put in the fridge. Doesn't sound like it was a fresh pack. The cold temperature and foil on top allowed it to carbonate.

 

[Spartan1979]

Could be. 36 hours on the stir plate has always been enough. I'm surprised it would be fermenting after cold crashing it.

 

[marc1]

Could be. 36 hours on the stir plate has always been enough. I'm surprised it would be fermenting after cold crashing it.

It's a lager yeast, so it likes the cold. Probably not an optimal fermentation at that temp, though.

One of the Escarpment Labs videos mentioned that Cal Ale can stay active at fridge temps, so it's not unheard of.

For starters, I run 36-ish hours with stirring, then a day or 2 on the counter, and then to the fridge for crashing.