From time to time, starter gets a bit out of balance. Either a bit too acid, or a bit too alkali. Mostly, this comes as a result of neglect, but it can also come about from the home baker not being able to read the starter correctly.
People sometimes 'over feed' their starters, and it can end up with this process being the remedy as well. Often, they'll just throw it out and start again. I advise against this course of action, due to the simple fact that the essence of a starter doesn't ever die - it just gets out of balance. By throwing it out, you are throwing away the flavour you want to get by making sourdough bread in the first place!
TYPICAL SYMPTOMS OF A SICK STARTER
Starter smells funny - like acetic acid. Or like mould.
There might be a crust on top.
There might be liquid sitting on top of goop.
Or, a super sticky goop, no liquid at all, covered in mould.
These are all common starter ailments, and all have different causes and possibly remedies.
In all cases, the acid/alkali balance in your sourdough starter is out of whack. This happens when:
you don't feed it, and the micro culture of yeasts, bacteria and fungi and enzymes begin to break the structure of the food (flour) into its component parts, liquid, solid, and waste.
you overfeed it, which occurs when you begin a starter and you get nervous that it hasn't been fed and might die.
it suffocates, and you get that strong acetic acid smell.
If you have a crust on the top, remove it. It makes an excellent food for compost heaps, in that soil cultures actually feed on it, and it acts as a compost nutrient by increasing microbial activity in the soil.
Break it up before you put it in the compost - it will convert quicker.
If you have a liquid starter, and the liquid has separated from the carbohydrate, you have a 'hooch', which is a mildly alcoholic substance. You can either pour off the 'hooch', then feed the starter as you normall would, or simply add a bit of flour and stir it through to thicken it. Usually I will do the latter, because hooches are not such a problem - but it may be smelling like vinegar. If so, then pouring it off is the better course of action.
A liquid starter is generally fed with one part flour to one part water. This ratio varies a bit according to the type of flour you use - wholegrain flours soak up more water. Nonetheless, if your starter has produced a hooch, it will need to be made thicker in future. The hooch actually causes the starter to drown, because the carbohydrate underneath can't get any air!
If you can smell acetic acid, your starter has suffocated, and fermentation has become anearobic. The remedy for this will involve quite a few feeds. You will need to pour off half, or use it in a dough (though the bread will taste a bit acidic). Then feed it in the normal manner. Repeat this process a number of times, a few days apart, until the acetic acid smell is very faint, or gone completely. Then let the starter rest for a week or more - and be sure there is at least the same volume of air in the container as there is starter. What you are doing is converting the anearobic fermentation back to an aerobic one. Patience is key.
If you work with dough sourdough starter, or desem starter, you might have seen a starter which looks like the one in the photos, after many months of neglect. I allowed one of mine to become deeply mouldy to show how to redeem it for the website.
These come back very well indeed, after removing the crusty outer layer. The inside, as the photos show, is a thick and creamy and very old dough sourdough starter, almost ready for use. I simply fed it with a small amount of flour, and used it an hour later. It made the most sensational brown rice and wheat sourdough the very same day!
Here is a chunk of the crusty stuff sliced from my old dough starter. This became a family of worms' multiple lunches.
For a dough starter, feed with two parts flour to one part water. This is a thick mixture. It will help to stabilise the sourdough starter, and create a slightly different balance of enzymes. By thickening sourdough starter, it does become slightly more sour in taste. However, this can be offset by using less as a proportion of the flour weight in recipes.
You should aim to roughly double the total volume of the starter you have, and thicken it at the same time. This is a visual thing. You don't need scales for this.
REINVIGORATING A SICK STARTER (AND CONVERT IT TO DOUGH STARTER AT THE SAME TIME)
Here is a step by step breakdown of how to feed and reinvigorate 'rediscovered' (inert, mouldy, half dead, whatever you want to call it) Sourdough Starter.
I'm showing you how to make it into a dough starter, because if you have had problems with your liquid starter, the best remedy for most of them is to thicken it up to a dough so that you don't have to feed it so often.
After you have removed the crust or hooch, do the following steps:
Add a little warm water to the starter, and stir the starter through the water with a whisk or large fork. You might need to break up the cleaned starter with your fingers so it disperses through the water.
Then add flour, a scoop at a time. Keep adding until you've got something resembling a very wet, or ‘soft’ dough, and begin folding in the flour. I just run my fingers through the dough like a rake until it starts to clump.
Then, as it begins to thicken, turn it in using your spoon or the fingers of one hand. You should end up with something you could knead.
A bit of kneading, also with one hand is good - but not too much. This just expels the excess acid to get soaked up by the fresh flour in the mix.
Make sure your container is large enough for the starter you are making - I recommend allowing about the same volume of air as starter in the container.
Put it away in the fridge.
Finally, after this feed has softened (which is generally after a few days to a week in the fridge), add some more flour. This time, the starter will be quite soft, and the flour will go in more easily than it might have a few days ago.
Leave the other in the fridge to ferment slowly if you choose - now that it's thicker, it will keep substantially longer.
Of course, if you are a frequent baker, you may prefer to keep your liquid starter, rather than converting it to a dough, as we have done here. If this is the case, stick to the ratio of one part flour to one part water, make twice the amount you intend to use each time, and keep feeding it at least each time you make bread. Essentially, the thicker the starter, the longer it takes to ripen.
Okay, so healing your starter is not something you are really up for. I get that. So, follow the link to our School of Sourdough website and you can buy some there. If you are in Oz, the freight is free.
Orders from outside Australia can't be supplied, due to various and varying quarantine issues.