Yeast starter finished?

[seanppp]

I'm doing my first lager yeast (may me irrelevant to the question, not sure) and it's been on the stir plate for about 18 hours. I've read that the yeast is finished after 18 hours, and one should stop the stir plate and crash the yeast at that time.

However, I'm still seeing a lot of bubbles floating to the surface, so I'm wondering if that means the yeast is still working and I should give it more time? Are the bubbles CO2?

What are the bubbles and do they mean I should continue the starter?!

 

[skw]

The bubbles are CO2, yes. CO2 bubbles don't mean there is fermentation happening at this very moment - as you can clearly observe when you pour a bottle of beer.

However, personally I like to pitch my yeast starters at high krausen - if you have wort waiting for yeast, now's the time to pitch.

 

[seanppp]

I don't want to pitch this one at high krausen because it's a lager starter that is big and since at it was run at room temp there is a lot of nasty stuff in there that I don't want to put into my beer. I prefer to wait until it's finished, then crash and decant. I'm just curious if the CO2 bubbles mean it's not finished yet.

 

[EarthwormJim]

After 18 hours, it may be done but it may not be. I have had some that were slow to start that stayed on the stir plate two days before I thought it was time to crash.

I would say that, normally, co2 bubbles doesn't mean fermentation is happening, but in a starter on a stir plate the co2 comes out of suspension very quickly. If there are co2 bubbles, I think it is still fermenting. But, the bubbles may not be co2. If I am making a smaller starter even with the stir plate at the slowest speed the vortex will hit the bottom of the flask and it throws off air bubbles.

I would say to stop the stir plate and let it sit for like 15/30 minutes. If the color looks right, there are no little co2 bubbles and it starts settling out, it is probably ready to crash. Even if it's a little early it wouldn't be that big of a deal, it isn't like you have to worry about bottle bombs, you just might be a little low on your cell count. But leaving it on the stir plate a little too long won't hurt it either.

 

[seanppp]

Thanks for the replies. As a side note: I ended up crashing the starter and decanted a moment ago to pitch some new wort to grow it up some more, and tasted the decanted wort. It tastes like a delicious English Ale fermented at say 70F! Nice English-like Esters and a beautiful flavor profile! The yeast is WLP802 Budvar Lager. Does anyone else have this experience? I was really flabbergasted! I think I'll save the decanted wort from the next stage and bottle carb it in a bottle, maybe with a couple hop pellets in there. Does anyone do anything like this?

 

[kh54s10]

What are you using for your starter wort? I would imagine light DME, as most use, no hops and fermented at high temperatures would be disgusting... I have never tasted any.

I run my starters for at least 18 hours and up to 24 hours when I see good activity. There may still be fermentation occurring, but that is not what you are concerned with. You are looking for cell growth. The yeast will reproduce until they have cell counts enough to ferment the beer, then most of the activity goes into fermenting the beer. So after the 18-24 hour time frame, the cell growth slows enough that it is no longer necessary to wait longer.

 

[day_trippr]

My typical starter routine is 18 hours on the plate, overnight crash, morning decant, allow to warm while brewing the wort, then pitch in the afternoon.
I check the FG of the spent beer on occasion and it's always been in spec for the strain.

There's enough yeast in that pitch for 5+ gallons of 60 to 100 point beer to hit FG in five days.
Seems to me it shouldn't take long for it to rip through 2 liters of 35 point wort...

Cheers!