How Your Sourdough Starter Actually Works

Sourdough starters are incredible little things. Flour, water, time - all of that equals a bread rising agent. Isn't nature clever?
I've mentioned before how a sourdough starter works, but I thought today I might go a little more in-depth about it and touch on some of the benefits and reasons to make sourdough bread.

One of the things I remember first wondering about when I was new to sourdough, was how did the sourdough starter possibly stay fresh? Surely mixing flour and water together and leaving it to sit on the bench for several days would result in a mouldy, smelly mess? Why then, did the starter not only bubble to life, but stay fresh?
The answer is lactic acid. It's the same thing that keeps pickles preserved in traditional lacto-fermented foods. Lactic acid is produced during the fermentation process, and whilst the naturally occurring yeast is happy to live in harmony with it, other bacteria aren't. The exact acidity of the starter depends on your environment, flour and water. Whilst of course sourdough will always be similar, different starters will have very slight differences in characteristics. This unpredictability is partly why commercial bakers prefer to use commercial yeast - control.
Baking artisan sourdough bread is easy enough though, and way more fun than adding a teaspoon of yeast from a packet to a bowl of flour!


But where does this wild yeast come from?
It's naturally present in most grains and flours, and also on the surfaces of fruit and vegetables. Yeast breaks down, or "eats", the starches and carbohydrates in the flour. This process produces carbon dioxide and ethanol. The carbon dioxide is what makes the bread rise, and is visible in your starter as the bubbles.

Because sourdough is a fermented product, a lot of the starches are broken down in the process, making it a lot easier for your body to digest it. Soaking and fermenting (aka sourdoughing!) flour also breaks down phytic acid. Phytic acid inhibits the absorption of the majority of the vitamins and minerals contained in the flour, binding them together so that all your body receives is a tiny percentage and some starch. Sourdough breaks this down, meaning bread made this way actually has some nutritional value!
The longer proving and bulk fermenting times of sourdough also help break down gluten into amino acids, which is why some people who are sensitive to gluten find they can eat sourdough.

All this talk of fermenting that surrounds sourdough is what stopped me from trying it for quite some time. I didn't like "sour" or fermented foods (due to a few bad experiences with them), and when I heard lacto-fermented pickles described I pictured cucumbers floating in milky coloured liquid. Yuck!
A friend dropped around a jar of lacto-fermented pickles one day (unaware of my aversion to them) and I was surprised to be faced with a jar of what appeared to be ordinary pickles. And the taste? Oh my goodness, pickle heaven! Even people who don't like pickles would have to like these ones.

I think discovering that these pickles actually tasted pretty darn good made me think that sourdough might not actually be that sour. That and all the beautiful photos I kept seeing of it around the internet, finally whittled away my aversion and I had to try it out for myself.

I'm so, so glad I did!

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Have you tried eating or making sourdough yet?
I hope you've enjoyed this article and it's made you understand just how amazing your sourdough starter really is.

Happy baking!

Sarah x

If you enjoyed this post, you may also enjoy my eBook, Spelt Sourdough Made Simple.

Filled with delicious recipes designed for baking with whole spelt flour (and other variations of spelt) with no mixing in of other flours - this is truly 100% spelt sourdough. Also suitable for whole wheat flour baking. Learn more or purchase your instant download copy here.


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