wild yeast taking over?

Question

I brewed a belgian triple last week. I had a starter going using white labs trapist yeast but it didn't take off, must have been a bad vial. In the meantime the batch was sitting in the carboy waiting for yeast. I picked up a packet of wyeast trapist yeast and pitched that into the same starter to get it going.

Problem is: while the starter was going the cooled wort in the fermentor started to ferment without me pitching anything. It didn't get going to hard by the time I pitched a really good size starter into it.

question is: What is going to be the effect of whatever go in the batch to start it fermenting, and, since I pitched a really healthy starter into it that made the fermentation take off, will the yeast I pitched take over and still make a good tripel?

EDIT: for clarification: When my first starter didn't take off, I added more yeast to it (wyeast). In the meantime, while waiting for the wyeast starter to get going the carboy of wort started to ferment on its own.

Answer 1

There's a strong likelihood that the "wild yeast" that started fermenting your wort is residual yeast in the carboy (or other equipment) from your last batch. Something wasn't properly cleaned and sanitized, and the microorganism in highest abundance is generally your last yeast, so that's what has the best odds of survival.

If this is the case, though, the yeast may or may not bear strong resemblance to the last yeast. Because the colony has repopulated from a relatively small sample, with unknown origins and health, I would expect the aroma and flavor to resemble the parent yeast, but with possible profile differences due to the means that the yeast were "selected" and the limited base for the genome.

You could make observations about the character of the fermentation, krausen, trub, aroma, and flocculation (and later, the flavor) - these would not only hint as to whether these yeast are the children of those you recently used, but might suggest where the contamination came from - for instance, if this yeast is exactly like your last yeast except more flocculent, then it would be possible that the colony started from yeast cells on the bottom of your carboy which were the first to flocculate in the last batch.

Answer 2

Unless something bad happened I think the slight foaming you saw on Wednesday was the original yeast and not wild yeast. Perhaps the wort was too hot or too cool when you pitched the first time and it took a while to kick in or as you said a bad/old vial. The wyeast trapist yeast (what little bit grew) and the white labs trapist yeast will both be active for the fermentation. The beer will be just fine.

Answer 3

Well your beer will definitely be a "wild brew" so there's nothing else to do but sit and around and see what happens. And I do mean "sit" because you'll probably need to wait 5-6 months to make sure the wild yeasts have done their thing to completion before you bottle.

I'm glad you pitched the Wyeast instead of chucking the whole thing. All you can do now is give it time. You might want to do a little research on how safe the final product is. Since its not primarily fermented with Saccharomyces Cerevisiae, there could theoretically be a danger in drinking it, although probably not. If the beer smells like "beer", then you are all good and it wasn't wild yeasts! Drink up!

The Mad Fermentationist recently experimented with wild yeasts as primary yeasts and he's prob got some good info, so google him and read his blog.

I'll say that probably the beer will be pretty nasty in the end, but you never know. Could be wonderful. Scratch this, sounds like it will all be fine.