How to revive a mouldy sourdough starter

It’s possibly a vanity project but I refuse to let my sourdough starter die. I’ve had it for about 4 years now, through thick and thin and although I’ve neglected it a few times, I’ve always managed to revive it with success, even if when it’s layered in mould!

I believe that a stronger, more resilient sourdough will be created from a nearly dead starter being revived so I would always recommend that you try to get it back over starting fresh.

If you need help boosting a dead looking sourdough, the sourdough starter not bubbling article to fix your issue.

A mouldy starter

Why does mould occur on sourdough

Mould spores exist everywhere in the environment. Whilst a sourdough is generally a strong and powerful substance that resists mould, occasionally it can still appear. The most common reason for mould is caused by neglecting the starter from being fed. However, mould spores can enter the sourdough, thrive and multiply, ruining your sourdough dreams.

How to prevent mould occurring in a starter

If you haven’t neglected your sourdough, try moving somewhere where foreign objects can’t enter it or using a tighter lid to cover it. If the issue still persists, try bottled water and/or consider changing your flour.

How to fix a mouldy starter

Depending on the level of mould on the starter, it might just be a thick crust of mold that you can peel off and rescue the good stuff underneath. If it is more deep-rooted, dig to the bottom of your sourdough container and you should find a patch that isn’t moldy. I’ve never not been able to find a patch that isn’t moldy when doing this, you only need a teaspoon’s worth.

Take a small pot and mix a teaspoon of sourdough with roughly 30 grams of water and 30 grams of flour and cover. The following day, discard some of the starter leaving just a teaspoons worth in the pot and repeat the feedings.

Repeat this for two or three days, moving to a bigger pot and refreshing as you normal. After a week or two, the sourdough will be fully revived!

Here's a video to explain the process in detail:

Can a sourdough be too mouldy to fix?

Even if it looks like it on the surface, peel back the skin that’s formed and see if you can find an area that isn’t mouldy. If the mould is everywhere then you will have to throw it away and start a new one.

The mouldy bread experiment

The mouldy bread experiment was a well-shared test which shows how quickly mould grows on a slice of bread. While it isn't a bread making related test, it uses a slice of bread as the base of the experiment. After touching the bread with mouldy hands or household objects the bread is stored in a sealed environment until mould grows on its surface. 

The results show just how much bacteria is on our hands and many of the tested objects. The learning is to make sure that we wash our hands regularly.

To see my full guide on sourdough, view the how to make sourdough bread page, for a simple starter recipe and a deliciously easy sourdough bread to make.

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