Zech don't worry you won't catch anything nasty, the yeasts come from the flour, not the air, so unless you are using rotten flour....Zech wrote:I'm a bit nervous about catching wild yeast in case I get something completely different by mistake. Could I get a sourdough started with commercial yeast, then carry on in the same way?
You can use commercial yeast, but you are missing out on an important part of a natural leaven, complexity and flavour, as commercial yeast has only one strain of yeast.
If your sourdough starter is seperating it probably means it is being left too long between refreshments. You need to refresh your starter once a week if kept in a fridge. Once it has separated you might be able to recover it but it will probably be too sour, so it will need several refreshments to get back to normal, probably easier to start again.