I always think that sourdough bread making is partly an art and partly science. There are lot of things that can go wrong or can have a negative effect on the final taste, crust and look of your bread.
But it all starts with a sourdough starter! If your sourdough starter has gone bad or is not strong enough to rise the bread, then you will end up with tough bread with an enclosed or gummy texture.
Over my 25 years of baking bread and sourdough I’ve come accross starters that have gone bad, but most of the time there was always a way to save the starter. So, here are my favourite tips on how to tell that your starter has gone off and more importantly how to fix it.
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Can sourdough bread starter go bad?
First of all, how bad is bad? As you will see from the rest of the blog post, sourdough bread starter can be saved if the starter hasn’t gone completely bad. But if you leave your sourdough start neglected for long enough, then yes, it will go bad.
The starter live cultures will first eat all the available food (the fresh water and flour that you’d normally feed your starter with) and then they will start to die as they don’t have anything else to survive on.
You’ll see that the colour changes and you might get a black water (called hooch) separated on the top of your starter. You’ll eventually get mould and the sourdough starter will start to smell really bad too.
This process takes quite a while, so you don’t need to worry that if you leave your starter for few days it will go completely bad. It takes time and there are a plenty of ways to save your sourdough starter before it get’s that bad.

What to do if my starter is bad?
I’ve given you detailed answers for each scenario, but in general, here is what to do.
Depending on how bad it is, you could first try to revive your sourdough starter by taking half away, feeding with fresh flour and water.
If that doesn’t help, then you can use the starter for baking or flavouring bread, pancakes etc. This is on the understanding that the sourdough starter is cleaned (no black water on the top, no mould) and moved to a clean container.
If the sourdough starter has too much mould or smells really bad, then I would probably just use it for other domestic purposes (such as making playdough, flour glue etc.) or put it into a compost bin.
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So, how do you tell if your sourdough starter is bad?
But before your sourdough starter will get bad, there are some signs, that will tell you that your sourdough bread is getting less active. This will give you the chance to save your sourdough starter and carry on baking your sourdough bread.

The sourdough starter is flat on the top and there are no bubbles
This is one of the most obvious signs of a sourdough starter, that’s not very active. The top of the sourdough starter will be flat with no visible air bubbles and no signs of life.
How to fix it: Take 1/2 of the inactive sourdough starter away (bake with or use it for your compost) and feed it with strong wholemeal or rye flour and water. Keep it somewhere warm and keep discarding the starter and feeding it until the starter is active again.
There are no bubbles visible from the side of the jar
The next obvious sign is no bubbles on the side of the starter container either.
How to fix it: Follow the tips above, but use extra ingredients (such as grapes, apples or potato flour) to revive your sourdough starter as it’s even less active then if there are no bubbles on the top of your starter.
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The starter didn’t raise at least double in size since you’ve refreshed it (fed it) last time
This is a sign of a slightly underperforming sourdough starter and the chances are that with a little bit of love and tender care you can revive your sourdough starter and nurse it back to health.
How to fix it: Apart from the tips suggested above, the next solution level up is to feed your sourdough starter twice a day (instead of just once a day). Keep the sourdough starter somewhere warm in between the feeds.
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You have left your sourdough starter at room temperature and forgot to feed it
If you leave the sourdough starter in a warm environment the yeast carries on developing until it hasn’t got anywhere to go. If you don’t feed the starter (add fresh flour) the wild yeast soon runs out of food and will start to die off.
How to fix it: Re-start feeding your sourdough starter with fresh flour and water. If your sourdough starter is very limp you can add grated apples or yoghurt to help develop extra live bacteria culture.
The starter has developed mould
This is an obvious sign of sourdough starter neglect and it’s more serious than just not feeding it. The mould can affect the ability of your sourdough starter to grow and be active again.
Mould in flour is not good news and similarly like other flour mixes (such as shop bought pancake flour mix) sourdough starter can go bad.
Some people recommend not to revive starter with mould, because the mould spores are very likely grown into the lower parts of your sourdough starter (although the mould might appear just on the top).
I’ve successfully revived the sourdough starter with a small amount of mould, so I know it’s possible, but I know some people might prefer to get rid of mouldy starter instead of saving it.
How to fix it: You can try to revive the sourdough starter by removing the mould and a large part of the top layer of your sourdough starter. Using another clean spoon take out small amount of sourdough starter that has not been compromised and place it in a clean container.
Add fresh flour, water and if you like add squashed grapes, grated apples or some yoghurt to help to develop live bacteria again a little quicker.
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The starter has a black water on the top
If you leave your sourdough starter for too long without feeding, it might develop a black layer of water on the top and the water separates from the rest of the flour mix.
How to fix this: Remove the black water and the top layer of the sourdough starter. Move the sourdough starter into a clean container, feed it and keep it warm. Carry on discarding and feeding until your starter is active again.
The starter smells very acidic and strong
This can happen if you leave your sourdough starter at a higher temperature environment than recommended – 23-25C ( lower temperatures are fine).
How to fix it: You can try to mellow the acidity by removing some of the sourdough starter and feeding the rest with fresh white flour.
Depending on how acidic the smell is, you might like to take away up to 2/3 of the old sourdough starter and add fresh flour and water to just 1/3 of the original starter.
This blog post was originally written on 13 October 2022 and last updated on 13 October 2022
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