I've recently branched out into fermenting things that aren't beer. I reckon that, for the last 25 years or more I haven't had a single batch of beer that was ruined by spoilage organisms of any sort. I put this down to 3 things: Decent hygiene, purging every deadspace from a large CO2 cylinder, and possibly living in a remote area in Scotland - I hardly see fruit flies etc (although I am paranoid when I do!). Luck must also be a player, but after this length of time not a huge one, I feel. What I'm worried about is: could this all be about to change?? For some reason, I've just become interested in a variety of other fermentation processes. I've made my own bread for some time, to date using baker's yeast, but I've now got 3 sourdough starters on the go. These contain both yeasts and bacteria - and ones that are happy to ferment carbohydrates at room temperature in anoxic conditions - so if they will grow in, and therefore contaminate/spoil beer, my CO2 purging will be entirely futile. Worse, perhaps, I'm also having a go at more esoteric stuff. At the moment, a type of yoghurt that works at room temperature, and also a thing called "ginger kefir water". This is apparently another yeast/bacterium symbiosis that ferments sugars happily at room temperature in the absence of oxygen. So, it seems to me, that the probability of some of these "wild" yeasts and bacteria getting into my beer are quite high unless I step up my procedures to virtually genuine sterilisation, which is clearly not practical. My question, therefore, is this. Has anyone had problems with their beer which they put down to cross-contamination from other fermentation processes? I'd appreciate the benefit of any experiences, positive or negative. I might also try inoculating a few bottles of beer ( when I produce an indifferent brew!) with a few of these things, just to see if they take hold. Oops!! Just realised - I thought I was posting this under "General Beer Brewing Discussion.. " and not "General Beer Discussion". Ah, well - shows it's time for bed!