Some Leavening Thoughts

A lot of my loaves are raised with natural leavens, rather than store-bought yeast.

There’s a lot one could say about natural yeasts, wild yeasts, sourdough starters, levain, leaven, what have you. I'm not going to say much. You can read elsewhere about how a good natural leaven is a symbiotic mixture of different sorts of yeasts and bacteria that together act to keep nastier organisms at bay. Each of the inhabitants of a good culture makes life better for the others in different ways; changing the acidity of the mixture, eating some of the nutrients, excreting others, creating specific flavour molecules. Temperature, hydration and feeding schedule affect which bugs do best, and so affect both the raising power and the flavour. It’s a minefield.

A minefield through which I plough with gay abandon.

I have two leavens. One is derived from a culture I started myself about 20 years ago. I tend to call that one “the starter”. The other is a pasta madre that is supposed to be a centenarian; I call that one “the madre”. With both of them, there’s a build phase, where I take the stored leaven out of the fridge, feed it up once for the madre and two or even three times for the starter before making the dough for the bread. The madre is kept at about 65% hydration, the starter at 100%. The starter I generally feed before putting it back in the fridge. The madre goes straight back in the fridge.

I only ever use the madre for one basic kind of loaf, usually with a good percentage of wholemeal flour and often with nuts and grains and stuff too. The starter gets adapted in one of three ways. If I’m going to be doing a rye loaf, I’ll feed it with 50:50 rye and water, usually twice, and then make the dough, reserving 10–20 grams for next time. There’s also a kind of San Francisco sourdough recipe that I use, from Dan Lepard, that gets fed with ordinary soft flour and a half and half mixture of milk and yoghurt, usually three times to bulk it up.

Those shifts in the flour and the liquid definitely make a difference to the leaven. Fed with rye, it seems to rise much more rapidly, especially the second time. Watered with milk and yoghurt it seems to become more -- how can I put this delicately? -- snot-like, taking on some of the qualities of Finnish long milk, or viili. And I’m pretty sure that they also affect the flavour of the final loaf, although life is way to short too bother finding out.

Some people definitely like to keep a whole lot of leavening cultures going. My life and baking style don’t suit that. So I’ve just got the two (and I’m pretty sure I could ditch one of them, but somehow that wouldn’t feel right). The point is that it really is rather simple to convert them around. The make-up of all the different bugs living in divine peaceful harmony probably doesn’t change all that much, although I don’t doubt that it would given a bit more time. This attitude also makes it easy to convert a starter at one hydration to another. Just do it. If you start with 10 grams of the original, after two feeds at the target hydration, you’ll be as close as makes no difference. Again, I’m sure the balance of bugs would shift further if you kept it up for longer, but if you just need to follow a recipe that calls for a stiffer leaven, start stiffening with the first feed and you’ll be fine.