What is a Sourdough Starter
A sourdough starter is how we cultivate the wild yeast in a form that we can use for baking. Since wild yeast are present in all flour, the easiest way to make a starter is simply by combining flour and water and letting it sit for several days.
Making a starter is a simple process of combining flour and water, which is then subsequently ‘fed’ or refreshed with more flour and water over a period to encourage the yeast to ferment and the bacteria to develop.
Once established, your starter will go through a predictable cycle of bubbling, growing to about double its size, and then falling, and will take a similar time to complete this cycle if held at a consistent temperature.
How To Make Your Own Sourdough Starter
Click here for a step by step guide to making your own sourdough starter.
How does a Sourdough Starter work?
Yeast is present on the surface of cereal (eg wheat, rye) grains. When those grains are crushed to flour, and that flour is then mixed with water, the yeast will begin to multiply and thrive. As the yeast feed on the flour, they produce carbon dioxide gas.
Over time, if more flour and water are provided, and the mixture is ‘refreshed’, the yeast colony will become more concentrated. Eventually, the mixture will produce enough gas that, on adding it to a dough, it will raise that dough to form bread.
Alongside yeast, bacteria also thrive in the mixture. Those which are beneficial to sourdough making, including lactic and acetic acid bacteria, will multiply well alongside the yeasts present.
These bacteria produce acids that contribute to the flavour and texture of sourdough breads. These acids may also help preserve breads made with the mixture, lengthening its shelf life.
What does ‘hydration’ mean?
Starters are often referred to as a percentage ‘hydration’, for example 100% hydration sourdough starter. The percentage indicates the hydration of the flour in the starter.
For example, a 100% hydration starter would be made from and fed with equal quantities (by weight) of both flour and water, or 1 part flour and 1 part water.
The hydration of a starter not only affects its consistency but also how quickly it will ferment. A less hydrated starter will be thicker and slower to ferment, hence requiring less feeding.