Waiter, there's a mold in my yeast.

So.. as I'm getting ready to make a starter of a month old Belgian Abbey yeast that I had stored in my fridge, I notice a furry little blob of mold sitting inside the lid of the tube. The yeast itself looked/smelled fine but I tossed it out.. but then got to thinking..

What if I had made that starter, seen no sign of mold infection.. could you then assume that the yeast had out-competed (at least temporarily) the mold for nutrients? Would the mold show up later? At what ABV will mold die?

Oh, and another question.. seeing as how I will now have to procure another sample of the aforementioned yeast. I'm thinking of recultivating from the beer that I recently brewed with it, it's a dubbel at 7%. Nothing out of the ordinary, like I said, it's been in the bottle for almost a month.. If I recultivate from bottle, what are the chances that I'm gonna end up with a mutated yeast? I should mention that I live in Sweden and the nearest LHBS is an hour drive from here (open only until 17:00 on wednesdays) and that buying a new yeast will set me back a handsome 20 bucks or so...

BTW.. this is my first post here! Love this forum..

Cheers

lasseg said:

as I'm getting ready to make a starter of a month old Belgian Abbey yeast that I had stored in my fridge, I notice a furry little blob of mold sitting inside the lid of the tube.

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Starters should really only be kept for less than two weeks. If you're going to need them longer, it's best to look at The Frozen Yeast Bank Thread. Not only will this keep your yeast fresher, done right you can virtually eliminate your yeast expense by harvesting and stocking up.

lasseg said:

The yeast itself looked/smelled fine but I tossed it out.. but then got to thinking..

What if I had made that starter, seen no sign of mold infection.. could you then assume that the yeast had out-competed (at least temporarily) the mold for nutrients?

Click to expand...

I've got no scientific background and this is "common sense musing" here - take that for what it's worth.

Firstly, that the mold could grow in the starter tells me two things. 1.) Conditions are right for mold growth in the starter wort. 2.) Everything that went into the starter wasn't sanitized.

Odds are, the mold spores were in the starter wort and would have taken hold given enough time.

As for out competing the yeast, I'd say no. That's a rough, but flawed, way to view the environment there. No two organisms have EXACTLY the same requirements; while both organisms need food, they may change their "eating habits" when they become stressed (yeast cannibalize themselves in rough times) and may begin eating stuff the other guys didn't.

Hi and welcome to the board!

As far as the mold goes, the original starter may have been infected or more likely the mold came from something else in your fridge. There is no way of knowing definitively at this point. Regardless, mold is present several days before you can see it, so by the time you see it, it is there in large numbers.

You may have had success using the yeast, but I would have tossed it too rather than risk wasting time and ingredients only to discover an infection.

I should drag out one of my microbiology texts to be sure, but I think that ABV has to be above %20 to be antimicrobial.

Thank you for your answers!