Maybe I'm just being a nervous nelly about my yeast starter...

[DRoyLenz]

... but I fear it may be infected, and I want to figure it out before I pitch it.

I have a 3 liter water bottle, and made a 1.5 liter starter, then crash cooled it, and racked off the beer, and stepped it up with another 1.5 liters of wort. I came back from work today, and it was clear that I had a blow-off problem.

Will my initial build up of yeast cause such a vigorous fermentation the second time around to make 1.5 liters or wort blow out of a 3 liter bottle? Or is there a legitimate risk that the starter is infected, thus creating the increased activity?

 

[Zen_Brew]

Yes it is completely possible for your stepped up starter to blow off and there be no problem. It depends on a lot of things like temperature, how you had the top of the bottle sealed, and how much fermentables there was in the second starter. Remember you were dealing with a much larger volume of yeast on the step up, so the growth phase can be more agressive when there are more there to start. Also you could have had some fermentables left from the first starter depending on how long you let it ferment out before crashing it.

 

[DRoyLenz]

I'm thinking that if it is an infection, the FG of my starter will be very low. I'll crash cool it, then take a hydro reading. If it is notably lower than 1.010, then I'll consider holding out until I get some new yeast and a new starter. Sound reasonable?

 

[Torchiest]

I personally would guess the chances of having an infected starter are very very slim. I've never had anything like an infection with any of my starters, and the two or three times I've had infections in my actual beer, it didn't cause any additional or more vigorous fermentation that I noticed. I could be wrong, but I don't think I've heard of that type of activity before.

 

[DRoyLenz]

shameless bump, hoping to get a few more opinions

 

[Wellshooter]

After it settles down and clears take a sample and give it the smell & taste test. It should smell yeasty like yeast bread smells, and it will taste, well, pretty darn good. That means all is well.