Many sourdough bread recipes call for a 'leaven' or 'levain'. If you're new to making sourdough bread at home, you'll need to know how to make a leaven, which is really easy! It's just a little off-shoot of your sourdough starter mixed with water and flour, then allowed to rise. Once it's doubled in size, it's ready to use.
Using a sourdough starter.
Homemade sourdough bread uses a homegrown yeast where wild yeast in the air and in the flour combined with water, start to ferment and become a sourdough starter. It takes about a week to grow and can be used indefinitely as long as it's cared for with regular flour feedings. This is called the main sourdough starter, or 'mother' sourdough starter.
Leaven is an offshoot of the main sourdough starter that is destined to make a loaf of bread. Pulling off a few tablespoons of sourdough starter and mixing it with flour and water will create the inoculation of yeast that you need to bake up a fantastic loaf of homemade sourdough. Once the leaven is mixed, it's set aside for 3-5 hours, allowing time for it to feed on the flour and ferment. A byproduct of fermentation is little bubbles of C02 and lactic acid. The leaven is happily fermenting and rising, becoming light and airy but also gaining strength to power your bake.
Leaven takes time
You'll need to wait to use the leaven until it's doubled in size and at its peak strength. Depending on the temperature, this can take as little as 3 hours or up to 5 hours. How to tell when it's ready? I've got answers! I show you in the video how to do a float test.
Get off to a good start
Before any sourdough bake, I pull my main sourdough starter out of the refrigerator 2-3 days in advance and feed it twice a day. Waking it up and allowing it to regain the strength it needs by using 3 x the flour to really give it a good boost.
The strength and performance of your leaven will be determined entirely of the strength of your starter. If your starter was starved, it won't perform as well as a recently fed and robust starter.
A mature sourdough starter
A mature starter is a sourdough starter that's been fed roughly 6-10 hours ago and is at its peak of fermentation with active gasses, bubbles, rise, and strength. It has an open airy structure with a jiggly surface. It hasn't yet begun to deflate. Mature starters can be used in making fantastic sourdough bread. I prefer, it actually - if I can time it properly. I'll feed my starter the night before I need it, usually around 10 pm. At 6 the next morning (I'm an early riser), it's all puffed and ready to go.
Using a leaven or a mature sourdough starter. You have options.
Using a leaven is predictable. You mix it, it rises, then use it when it's doubled in size. But it takes time, about 3-4 hours in my kitchen. If I start my sourdough bread process at 7 am by mixing the leaven, I usually can't get my final dough mix together until 11 am or so because I'm waiting on the leaven to rise (we call that "build). It's not a bad thing, it just takes planning on sourdough day.
Using a mature starter is my preferred way to go, but it takes a little pre-planning before sourdough day. The starter needs to be fed well at least a few days before using it and the starter has to have held its rise overnight. The big benefit here is I can get my final dough mix together at 7 am and I'm already hours ahead of schedule. I'm done with shaping and getting my loaf into the refrigerator by 1 pm at the latest. I LOVE that and it's the main reason I prefer using a 'mature starter'.
If you're new to sourdough:
I recommend you use the leaven method for now. After maintaining a sourdough starter for a little while, you'll start to see the predictable rise and fall, and you can decrease and increase the feedings to see how it reacts. Once you get it to holding a rise for 8-10 hours after feeding - then for sure consider using a mature starter in your bakes. It's more convenient and saves a ton of time.
How much leaven do you need for sourdough bread?
That depends entirely on the recipe. My beginner loaf calls for 25g sourdough starter, 50g flour, 50ml water. Once it builds, you'll need most if not all of it - somewhere around 90g. I have an intermediate loaf using multi-grains so I bump the quality up a bit, closer to 100g.
And this one is my favorite go-to recipe for homemade sourdough bread.
Finally, I want to include a link for The Fresh Loaf. It's my favorite online forum for everything sourdough. A great place to ask questions.