In this post you will learn the key differences between different sourdough starters, having a closer look on a regular starter, stiff starter and a liquid starter.

The water amount of each starter is the key difference

A regular starter is typically at a hydration of 100%. This means you have equal parts of flour and water in your starter. A liquid starter has a hydration of 500% meaning you have 5 times as much water as you have flour. A stiff starter (lievito madre) has a hydration of 50% meaning you have half the water compared to your flour amount. This is where it gets really crazy, just by changing how much water your starter has, you can influence the whole fermentation process and thus the final taste of your bread. Let me explain.

The microorganisms of your starter

Sourdough starters contain wild yeast and bacteria. The yeast is creating ethanol and CO2, the bacteria creates lactic acid and acetic acid (also sometimes CO2 and ethanol). You have homofermentative bacteria and heterofermentative bacteria. This is fancy term for bacteria that can change what they eat and what they ultimately produce during the fermentation activity (aka. POOP). CO2 makes your bread fluffy and ethanol induces alcoholic taste. However, that mostly boils during the baking process. The lactic acid creates you dairy notes, the acetic acid vinegary notes.

By adding water to your flour the amylase enzyme is activated. Amylase converts starch into smaller molecules ultimately yielding maltose. The same happens in your mouth if you keep bread in your mouth for long enough. The flour does this as the germination process needs energy. This is what the yeast is feeding on.

So does the lactic and acetic acid bacteria. On top of that they are also digesting the ethanol created by the yeast. Furthermore the lactic and acetic acid bacteria are eating the gluten of your flour. Gluten is a storage protein that’s broken down by water as well into smaller amino acids. This is what the germ needs to sprout too. This is important information for you, because with bacterial fermentation you will lose dough strength over time. This is good and bad. Good because the dough might become more digestible. You don’t feel so bloated after eating, bad, because the CO2 created can no longer be retained inside of your dough. Your dough will not be as fluffy. Ultimately your dough is going to become very sticky. Fun fact, that’s why it’s important to have a slow/long fermentation because it takes some time for the amylase to work the flour. That’s why a good dough shouldn’t be make in 1 hour. Try to aim for at least 8 hours of fermentation.

Now the unique composition of lactic and acetic acid bacteria depends on your starter. Please let your starter sit without feeding for 2 days at room temperature. Does it small like a bottle of vinegar? If it does, then your starter produces a lot of acetic acid. That’s nothing bad, but ultimately it depends on what kind of bread you plan to bake. If you want to make a hearty rye bread, then vinegary notes are great. Do you want to make a soft sandwich or brioche bread? Then I would not like to have vinegary notes. So this all depends on what kind of taste you like.

To suppress the vinegary notes you need to deprive your starter of oxygen. Acetic acid requires oxygen in the whole process to be made. That’s where a liquid starter comes into play. By submerging your flour mixture in water, you are suppressing additional oxygen from entering the fermentation process. Similar to a lake in summer times where the fish sometimes die in case no new oxygen enters. The flour starts to sit near the bottom of your starter. Over time the bacteria that only produces lactic acid will start to dominate and eventually take over. Your starter will mostly start producing dairy notes only. Warning - over time your microorganisms change and you can never go back! I’ve tried to go back to vinegary production with a 100% starter, but I can’t. I really like the flavor this liquid starter adds to your dough, it’s mild and dairy.

It seems though that at a higher hydration your yeast is also not as active.. I tested different starters and I measured how much each of them would inflate a balloon. The liquid starter lost compared to the starter at 100% hydration. Both of them lost to the starter at 50% hydration. I made all of the 3 doughs from the same source starter. So you could directly see the impact after just 1 feeding. Please check out the video, it contains a few additional interesting experiments. The outcome of this video was for me to then use the stiff starter to bake bread. I could confirm that the stiff starter creates very fluffy bread, that’s mild and not high in acidity. On top of that I made great sourdough with the cheapest low gluten flour that I could find. This confirms that the gluten munching bacteria isn’t as present. This is really cool to know, because normally you would want to get a high gluten flour to withstand the long fermentation, but the with the stiff starter that’s not needed. I still don’t fully understand why the yeast prefers the stiff environment. I have also not found literature on the topic yet. If you do find something please share it with me.

Here’s a quick summary of the different starters and their flavor:

# Liquid starter Regular starter Stiff starter
Flavor Dairy Vinegary or dairy, or both Vinegary or dairy, or both but more mild
Microorganisms Favors bacteria Bacteria and yeast Favors yeast

Depending on where your stiff starter is coming from the taste can be either slightly dairy, slightly vinegary or both. So in case you are a chaser of the pure mild dairy flavor consider converting your starter to a liquid starter before.

If you make a starter from fruit water then in many cases you don’t even have strong vinegary notes. This depends a lot on which bacteria you cultivate. My starter has been originally made with rye flour and just after a few days it would really smell very gross. If it does and you prefer milder sourness, then consider the liquid starter.

Liquid starter conversion

  1. Take 10g of your existing starter
  2. Mix with 50g of water and 10g of flour
  3. Next day shake the bottle, extract 10g, add 10g flour again, 50g water
  4. Repeat for another 2-3 days
  5. Please note how the smell of your starter is going to change

Using the liquid starter

Your liquid starter is ready to be used when you gently shake it and see bubbles of air coming to the top of the surface. I recommend to use around 25g of liquid starter (5%) in summer times and 50g (10%) in winter times (calculated for 500g of flour). As the starter is really liquid make sure to use a little less water. I typically subtract the liquid starter amount from the water amount required to make the dough. This then gives me the final water value I should use.

Please try putting a piece of bread in your freezer just to compare the taste the liquid starter adds to your dough. It’s crazy.

Liquid starter maintenance

I give my liquid starter one feeding before it stays good in the fridge for months. You can always dry a bit of your starter. It will take a little while for it to reactivate, but after a few days it’s good as new.

Stiff starter conversion

  1. Take 10g of your existing starter
  2. Feed with 50g of flour and 25g of water
  3. On the next day, take 10g of your stiff starter, feed again with 50g of flour and 25g of water
  4. The starter is very dry and mixing is a pain. I typically knead it on my bench
  5. Please repeat this for another 3 days, it takes time for your microorganisms to adapt

Stiff starter maintenance

After making a dough feed your stiff starter one more time. Then proceed and place it in your fridge. It will stay good for months. The best thing is to feed it 1 more time before baking. But, you could also just be using a little less starter for your next dough (5%). However, you are introducing quite a lot of fermented flour in the main dough, which can cause issues. So unless you know what you are doing, my recommendation is to give your starter one additional feed. I typically do that in the evening over night (10g starter, 50g flour, 25g water) and then in the morning I mix my dough.

Using the stiff starter

  1. The stiff starter is ready when you flip the glas you have over and you see pockets of air in the starter dough
  2. In summer times I use 10% of stiff starter calculated on the flour. That’s 50g for a dough of 500g of flour
  3. In winter times I use 20% of stiff starter calculated on the flour, that would be 100g

A note on autolysis

Some bakers like to mix a portion of the dough in advance. I personally don’t see the sense in it. I like to do a fermentolyse where I mix everything together right away. To slow the fermentation I use a little less starter. The autolysis as far as I can tell helps to the protease and amylase enzyme to do their work. Sometimes if your main dough fermentation is too fast biochemical reactions don’t happen fast enough. But to counter that I simply use a little less starter to achieve the same thing with a slower fermentation.

Leftovers

when feeding you will end up with leftover start that you don’t use. Please don’t throw it away. Store it in your fridge and then make some sourdough spice or a delicious bread out of it.

Closing words

I just wanted to quickly write this post down. I will be adding sources for everything asap when I have a bit more time :-). In general I can recommend the following books where many of the aspects are covered. But please also know that your starter is a symbiotic relationship of various microorganisms. This means that it doesn’t necessarily mean that all the research applies to your starter as well. Experimentation at home is required.

  1. Bakery Products Science and Technology. Y.H Hui et al.
  2. Handbook on sourdough biotechnology. Gobbetti et al.
  3. Highly Efficient Gluten Degradation by Lactobacilli and Fungal Proteases during Food Processing: New Perspectives for Celiac Disease. Carlo G. Rizzello et al.