Hydrometer sample fermented?

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stevehardt

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A month ago I brewed an all grain hefe. Took a hydrometer reading in a well sanitized hydrometer tube and recorded my FG. Wasn't being careful enough and accidentally left the sample in the hydrometer tube. When I found it 3 - 4 days later the gravity had dropped significantly. Looked like it had fermented in the chamber.

So when I brewed this weekend I deliberately left a sample in the well sanitized hydrometer tube. 3 days later it was clearly fermenting.

Is this caused by airborne wild yeast?
 
Heck yeah there is lots of wild yeast. Mix up some water, flour, add a bit of lemon juice and leave it out for a couple days and you got yourself a sourdough starter.
 
It wasn't necessarily wild yeast. Did the sample come from wort in which you had already pitched yeast? If not, yes it was a spontaneous fermentation. If that's a plastic sample tube, then just be careful, because it'll likely harbor whatever yeast went rampant in there. In that case you would never want to dump a sample back into your batch. Not that many of us do that, but some do.
 
I must admit I'm surprised. It was a well sanitized dip tube with a sample in which I had not pitched any yeast. I had no clue there was that much wild yeast out there. Lesson learned!
 
I had no clue there was that much wild yeast out there. Lesson learned!

I suppose we ought to be glad there is a constant supply of microorganisms floating around. If not, our ancestors would never have discovered fermentation in the first place!

Good example, we eat a lot of yogurt in this house. If I'm not careful, I'll get lacto in my wort. That's the microflora in my environment.
 
I must admit I'm surprised. It was a well sanitized dip tube with a sample in which I had not pitched any yeast. I had no clue there was that much wild yeast out there. Lesson learned!

Yeah man...leave food out for a few days and it will get moldy, lol
 
To illustrate the point even further, I have left my spent-grain bag open a couple of times. One bag sat for two days and it was clearly fermenting. The bag was much warmer than the environment and it smelled like it was fermenting too.
Luckily my beer was also fermenting nicely :)
 
My hydro sample sat out for a week by accident. Started bubbling like crazy, so obviously fermentation had taken place. Decided to add it to my leftover wort, the end running from the mash off my following batch; about a quart. (IOW, Gave it some more sugar to eat) Anyway, I understand it is wild yeast but how do I know it's "good", meaning safe to use. I plan on building it up as it has already increased in size. Smells like a hefe or a belgian. The whole thing interests me, but I want to be sure it's safe for consumption if I decide to use it.
 
There is a great passage on this in the mad fermentationist's book, american sour beers. I can't recall the process off-hand, but if you have access to this book it describes a safe way to accomplish this and commercial examples of wild yeast gathering such as at jester king. If I have the time and recall this, I'll try to make it back over here to help.
 

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