Yeast starter is carbonated

[SkinnyPete]

Made 1.5L yeast starter and due to space in my fridge, I split it into two mason jars. But them in the fridge for 4 days while it cold crashed. I put the top on the mason jar and apparently, carbonated the starter. I just decanted and it's carbonated. The decanted beer is in a glass and it's carbed. And reading only went from 1.040 to 1.022. I have no choice but to use this yeast since I'm about to start the boil. Is the Co2 in the starter going to negatively affect my yeast? Never saw this before because I usually don't cold crash for so long and usually not with the top covered.

 

[2thGuy]

The carbonation will stress the yeast some, and the yeast being cold that long will make it go a little dormant. While your fermentation will not be ideal, I think your yeast should be fine enough to make decent beer.

 

[SkinnyPete]

I woke up this morning to a nice continuous bubbling. Now, 24 hours after pitching, I've got a fairly large krausen. So far so good.

And let me just clarify for anyone who may have this same problem, finding this thread in the future, the starter was absolutely carbonated. I'm not talking about the foam that may come out after opening a vial or anything like that. I'm talking full carbonation, you could serve the decanted liquid as a beer. Yet, yeast appears to still be healthy enough. Time will tell. I have more of the same yeast standing by if it should stall.

 

[Jeremy17099]

I made a 2000 ml starter of conan. I cold crashed after 36 hours. I left it in fridge for 1 week with foil on top. Today i went to split it into 2 jars and it is very carbonated. Is the yeast still good? Is the yeast infected. I dont see how foil could keep enough co2 in to carbonate the starter.

 

[flars]

Sometimes I will just leave a finished starter on my work bench if I'm going to use it within a week. This way I know it has fermented the wort as far as it can and CO2 production has ended. With the extra time most yeasts will drop out the same as being cold crashed. I will cold crash the known less flocculant yeasts for easier decanting and dividing for pitching and the amount of yeast to save for the next starter.

 

[IslandLizard]

Your starter beer is naturally carbonated. No pressure needed. I usually drink it, a refreshing low ABV session beer. The yeast went dormant in the cold, but is fine.

Before you brew, just pour off the clear starter beer, leaving just enough behind to swirl up the cake later when you're ready pitch. Leave on the countertop while you're brewing so it can slowly warm up to room/pitching temps.

 

[IslandLizard]

The carbonation will stress the yeast some, and the yeast being cold that long will make it go a little dormant. While your fermentation will not be ideal, I think your yeast should be fine enough to make decent beer.

This is the first time I hear that carbonation stresses yeast. Where did you get that from? Just curious.

I agree that cold yeast is dormant, but after warming up and pitched into an well aerated or oxygenated wort it will perform as any other yeast. Their lag time may be a little longer, but I've never noticed it.

 

[Jeremy17099]

Thanks for the info guys. I Made another starter out of one of the jars last night. Looks like it is doing fine on the stir plate. I am making a 10 gallon ipa with mosaic hops and el dorado hop hash( first time using hop hash). Pretty excited to see and taste the results of the hop hash. Cheers.

 

[Hoppy2bmerry]

This is the first time I hear that carbonation stresses yeast. Where did you get that from? Just curious.

Isn't that one of the reasons a starter is swirled either manually or with a stir plate? Is that not why wine fermenters are swirled during primary, because too high a consentration of CO2 stresses yeast? This is what I recall reading here in the forum some time ago.

 

[Yooper]

Yes, c02 is poisonous to yeast. But how much is related to time and concentration.

I wouldn't think that the small amount of co2 in suspension in a starter would be an issue at all.

That's why when beer is fermented in a pressurized fermenter, a spunding valve is used to remove some of the gas. The pressure of the gas inhibits fermentation above a certain point.

Since the starter vessel isn't pressurized, I don't see it as a problem at all.

 

[IslandLizard]

Isn't that one of the reasons a starter is swirled either manually or with a stir plate? Is that not why wine fermenters are swirled during primary, because too high a consentration of CO2 stresses yeast? This is what I recall reading here in the forum some time ago.

No. A yeast starter needs oxygen to propagate, grow new yeast cells. That's why it needs to be constantly stirred, shaken or swirled, or have air or O2 injected. As a side effect, the amount of dissolved CO2 is also reduced during that process.

I don't know at what concentration CO2 stresses or becomes poisonous to yeast, but beer is never degassed, even 12% ABV beer.

 

[Yooper]

No. A yeast starter needs oxygen to propagate, grow new yeast cells. That's why it needs to be constantly stirred, shaken or swirled, or have air or O2 injected. As a side effect, the amount of dissolved CO2 is also reduced during that process.

I don't know at what concentration CO2 stresses or becomes poisonous to yeast, but beer is never degassed, even 12% ABV beer.

Right- but that's because when a beer is carbonated you don't care about healthy vital yeast. And in the case of a 12% beer, the yeast will be overcome by alcohol toxicity before c02 toxicity before it's carbonated.

There are plenty of papers written about c02 toxicity and yeast vitality. Since we're not fermenting in closed vessels as a rule (although some homebrewers do- that's why they have a spunding valve), it doesn't really come into play for us.

Meadmakers especially degas during active fermentation, since the honey in mead has low nutrients and the yeast can especially be stressed by high volumes of co2. Beer wort has far more nutrients, so this isn't such a problem with beer.