When parenting a sourdough culture, it really is like looking after a child. You have to keep it fed and control its environment to keep it happy. You can tell when it’s being looked after well as it’ll start smelling beautiful and have plenty of bubbles. Unlike commercial yeast, a sourdough starter goes through a long fermentation process. There’s a specific period wherein it’s ripe and best to use. But why is a ripe sourdough starter so important?
A ripe sourdough starter makes a big difference in the texture, flavour and size of your bread. Since more starch is broken down into sugar it’s going to produce a more complex taste. And as a leavening agent, combined with a higher concentration of yeasts and organic acids, it will produce a better rise.
Regular feedings and warm temperatures create a starter that is high in lactic acid bacteria (LAB) and wild yeasts. It takes a minimum of 7 days for hydrated flour to ferment to produce enough yeast and acids to make bread. Providing it’s looked after well and regularly fed, an older starter will be stronger and more flavourful.
Many bakers will cultivate a new starter for at least 28 days before attempting to use it to make bread.
A ripe sourdough starter will rise up to triple its original size. The rise will depend on the starter’s wetness or stiffness, and of course, the amount of ‘food’ (flour) that it’s fed. The general consensus for optimum starter’s ripeness is the window between it reaching its peak and when it collapses.
The point where the starter is just about to fall is when the amount of organic acids is at its highest. This is when the starter is most effective. Try not to let it collapse as this is when healthy bacteria decreases and unhealthy bacteria tend to increase. It’s fine occasionally, just don’t do it all the time! Adding a starter at any point in the window where it is at its peak will produce quality bread.
If there are still bubbles being produced by the starter and it is capable of peaking in 4-8 hours, you can still use your starter when it is not at its peak. In fact, some bakers prefer to do this. Chad Robertson, owner of the Tartine bakery chooses to use his starter 2 hours after it is fed. This provides a more aromatic flavour that’s going to be less acidic. But bare in mind, Chad has professional proofers where he can manipulate temperature to perfect conditions.
At home, it’s harder to achieve the perfect proofing temperature so I recommend that you use your starter at its peak. If you want to try this method, a home proofer like the one from Brod & Taylor is pretty handy. See: Brod & Taylor home proofer – or my DIY proofing box solution.
Besides being about triple in volume, a ripe starter should look very bubbly with a slightly foamy texture on the surface. More importantly, you should also take note of the smell. A ripe starter should be pleasantly sweet, similar to that of yeasty bread, but with a hint of sour notes.
Along the whole process, the smell of your sourdough will go through different stages. But if it smells like a nail polish remover or bananas, it’s not ready yet and you should wait for a bit more time.
Unlike a healthy starter, a weak starter will have fewer bubbles and very few (if any) on the surface. And even though you put the effort into feeding it, it won’t rise that high. It will also have a different kind of smell that will vary from alcohol, stinky feet, vomit, and aged cheese.
As kind of a general rule, if you can smell something sour, it means that there your starter is alive. Continue to feed it more for a couple of days or weeks until it gets to be stronger.
A sourdough levain is reliant on Lactic Acid Bacteria (LAB) and wild yeasts to make bread rise. Controversy, it is not just yeast in sourdough, LAB is actually responsible for the majority of its leavening ability. Initially, a new starter becomes a harvesting ground for wild yeasts. These are found mainly in the flour, but can also come from the air and the environment.
After a couple of days, enzymes start to break down the flour further and produce LAB. As they multiply, the starter becomes more acidic, thus, lowering its pH balance. The acidity of a sourdough starter is typically between 3 and 4 pH.
Only a certain number of wild yeasts can survive in these acidic conditions which force the wild yeast population to stop expanding. The result is a cultivated mix of wild yeasts and lactic acid bacteria.
To reduce the regular daily feeds needed to maintain a sourdough starter, it is quite common for a baker to keep their starter in the fridge. Sometimes starters get forgotten and left for a while without being fed.
Providing it is not mouldy, the starter can be used again easily. It will need regular feeds and discarding (as if it were a new one) to be able to bring it back to life. After a few days of feeding the starter will re-balance its pH levels which allow the wild yeasts to become potent again.
Using a small clean pot, mix a teaspoon of sourdough starter with roughly 30 grams of water and 30 grams of fresh flour, and cover it for a whole day. Keep it warm.
The next day, discard some of the starters and leave just a teaspoon’s worth in the pot. You can then repeat the process of feeding it.
Continue to do this for about two to three days. Move your starter to a bigger pot and refresh it as how you normally would. After a week or two, your sourdough starter will be fully revived already! If the starter does have signs of mould there is an extra step to take, but it can usually be rescued. To learn more information about this, you can view my how-to revive a mouldy sourdough starter post.
As to how it goes with almost any ingredient, measuring a sourdough starter should also be done by weighing. This allows you to get more accurate and consistent results each time compared to measuring it by volume or through cups. This is also the way it’s done in professional bakeries.
For the best results, use digital kitchen weighing scales that can weigh precisely up to 1 gram. This way, you can avoid leftovers and make the most out of your sourdough starter. See the scales I recommend for baking bread.
A sourdough starter should be fed when it reaches its peak. This, if kept warm should occur twice a day. Regular feedings keep the starter nice and active and prevent starving the bacteria. Methods to reduce feedings whilst maintaining activity are provided in the how to make a sourdough starter recipe.
If you want to keep your starter active at all times you’ll need to keep up with a regular feeding routine. But there is more to it than this:
Keep everything clean! A healthy starter produces enzymes that break down the bacteria it is fed. The main source of bacteria will be the flour that you feed it. If unwanted bacteria is introduced the starter has to waste energy trying to learn new ways to break them down. As long as there are few unwanted bacteria added, the starter will break it down and consume it. But doing so will alter its leavening ability, temporarily making it weaker.
This is why it is important to use clean hands, utensils and clean your starter jar regularly. It’s also the reason why it’s a good idea to use the same flour to feed your starter. The same bag of flour contains the same bacteria, switching regularly can weaken your starter dramatically!
Another way to best keep your starter is to keep its temperature the same. Enzymes operate best at different temperatures. Changing the temperature means the starter will have to use more of one enzyme, and less of one that is plentiful. This causes the starter to weaken, smell funny and be less effective at raising bread.
Well, providing there are some bubbles you can use a weaker starter to make sourdough bread. It just won’t be as effective and will need the dough to be kept warm to allow it to rise. Issues from using a weak starter can include:
See the sourdough starter troubleshooting article for more information.
Once your starter is looking active it is ready to use! You can follow this sourdough bread recipe for beginners if you wish, but any sourdough recipe from a reliable source should work. Remember, it is active when it’s tripling in size in 6 hours and smells nice and hearty.