Before we began using modern cultured yeasts leavened bread was made with wild yeasts which exist naturally in the air. I've always wanted to try making sourdough bread because I'm curious about the whole process, want to see what it tastes like and as an added bonus it's supposed to be very good for you.
It's pretty simple. Mix half a mug of white flour with half a mug of water in a sterilised glass jar. Shake it up and leave at room temperature. After 24 hours pour off half the mixture and discard it, top up the remaining mixture in the jar with equal parts of flour and water ... this is feeding the yeast. After four or five days the mixture looks bubbly and frothy which indicates that yeasts are now flourishing and you have an active culture ready to start baking with. Once the culture is nicely active it can be kept in the fridge and will then only need feeding once a week.
There are sourdough starter cultures you can buy in powder form which I tried out last year, but I killed it by mistake when I placed the bowl in a warm oven after baking earlier that day (thinking it would like the heat!). But this time I like the idea of utilising our own local wild yeasts and so I'm about to try again.
It's the frothy culture which is added to your bread dough to raise it and also impart a unique flavour to your bread. The sourdough process results in a more nutritional bread as it semi-digests the flour and releases important nutrients, making them available to us for optimum absorption. The process of sourdough proofing also results in a very low phytic acid content, something that remains high in modern yeasted breads. Phytic acid reduces mineral metabolism (Healing With Wholefoods, by Paul Pitchford), contains flora beneficial to the digestive system and the loaf stays naturally fresh for days, even weeks, after baking. Apart from all that, it's delicious and well worth a try.
For preparation and baking instructions try this website. I'll let you know how I get on in a week or two.