I've been sourdough baking for a few weeks now and have already gotten a bit experimental. I divided my starter into two jars and to one I added some of my homebrewed ginger beer. This ginger beer is made from a 'plant' of wild yeast and bacteria sourced from the air, ground & fresh ginger, sugar, sultanas and lemon pulp that I have fed it with at various stages of its life. (Before I get jumped on by any GBP purists out there, no this is not a 'true' Ginger Beer Plant.) I figured that adding a few extra microbe strains to my starter couldn't hurt.
The resulting culture was noticeably more 'healthy' than the 'plain' starter that had only been fed white and wholewheat flour, in that it rose much faster both in the jar and in a loaf. The bread was good - much loftier than my other sourdoughs so far, but the texture and flavour weren't quite as interesting as the bread made from the unadulterated starter.
SO, my question is, by adding yeasts from a non-cereal culture, have I actually created a sort of hybryd beast or 'sponge' that is not strictly a sourdough? I'm not trying to be puritanical: ultimately whatever works is good. But this did get me thinking about what 'defines' a sourdough starter. Is it a flour-based culture populated with any any yeasts and bacteria, so long as they are wild and not bought in a packet at a shop? Or is there something more specific about where these fermenting critters a supposed to come from, or where they would 'naturally' be found?