How do you know if you've captured unsafe beasties? In breads or in vinegars....
MtRider -well, the vinegar sure didn't smell or look correct
You don't, until too late.
I have no idea...but to me it would seem logical that if a person left their "catchers mitt" sitting outside to long it could begin to grow other stuff? Even with regular commercial yeasts (or friendship yeasts) you can't just set them somewhere and forget them??? I don't mess with yeast too much, other than using the foil packets I buy.
The commercial packets are sold as dryed powders for a reason.
And thank you, I could not remember the English term 'friendship yeast'. These were distributed in dough fingers, wax paper wrapped (before the days of zip log bags)(foil often retarded the culture).
I still can not remember the so-called generic scientific name for a safe yeast. I hope it comes to me.
A good established yeast (good or bad) will fight off any new yeasts forming in/from the 'mother'. That is how the yeast manufacturers you buy the packets from control their raw product. Same with 'mother of vinegar', 'vingar' to me...
My advice, if you do not have access to established mothers, then buy.
of the Librum