Detecting infections in raised yeast.

I have been washing yeast and/or building double starters for quite some time with no trouble until the last 6 brews. All of these were made from washed yeast (WL001) and had been stepped up with a starter. 3 of the 6 batches showed signs of infections after 3 weeks. Thus, I am unsure if the infections came from errors I might have had in brewing 15 gallon batches or if it were in the same yeast culture. I am wanting to throw out my remaining yeast that I have raised just to avoid this again. Curious to know if there are any thoughts on this issue of how to detect problems prior to pitching.

 

I second all of those things, IslandLizard.

And on top of that, you can preclude infections from washed yeast by overbuilding your yeast starters and saving the remainder in a sanitized glass bell jar. In exchange for a small starter each brew, you can propagate yeast ad infinitum, and if your sanitation is good, there's practically zero chance of an infection developing from your yeast.

 

I screwed up my initial post. I meant to say that this was yeast that I had built up from a fresh vial. After I drain the mashtun for my beer I usually run another 1-2 gallons of water to collect enough sugar to boil to make a starter for the other 1/2 of the larger initial starter. I di this with large amounts of success until recently when I had this run of 3 out of 6 beers with infections. Both of these were 15 gallon brews and either 1 or 2 of the beers showed infection at 3 weeks. Thus, I am very unsure of how to test the remaining yeast I have to see what would happen. Should I just make a larger 2 gallon test starter that I let ferment for 2 weeks with the remaining jar of suspect yeast?

 

Haha, why are you so tied to this particular vial of WLP001? It's not exactly a rare strain. I would consider that to be way too much effort to preserve simple Chico yeast. If you are sincerely concerned about this rash of infections, dump the yeast and bleach bomb all of your cold side equipment -- especially transfer equipment.

 

I know I got a lot of mileage from my one yeast vial. It is more just a general question to think about in the future. Most HB don't have a microbiology lab in their basement so I am more just curious on if there is a way to test the viability/purity of yeast samples in the future.