Sourdough Baking Without the Mystery: Starter, Feeding and a Good First Loaf

When I first started baking with sourdough, I soon came across two rules that were repeated almost everywhere, but rarely explained:

1. Discard most of the starter before feeding it.
2. Feed the starter with equal parts starter, flour and water.

I followed the rules, but I did not really understand why. Why should I throw away a starter I had just spent several days making? And why should equal parts flour and water be right whether I used white wheat flour, wholemeal rye, or a flour that absorbed far more water than another?

After a few years of sourdough baking, I think this is one of the things that makes sourdough unnecessarily difficult for beginners. You are taught a method before you are taught what you are trying to achieve.

Sourdough becomes much easier when you stop thinking of the starter as a recipe and start treating it as a small ecosystem. We give the microorganisms food, water, the right temperature and enough time. The balance between these factors determines how the starter behaves. Equal parts flour and water is only one possible starting point.

What is a sourdough starter?

A sourdough starter is flour and water in which a stable community of mainly lactic acid bacteria and yeast has become established. The yeast produces gas, which can raise the bread. The bacteria produce lactic acid and acetic acid, among other things. These add flavour, affect the dough and help the bread keep longer.

It is tempting to describe the starter as one particular organism, but it is more accurate to see it as a small workplace with many employees. Which ones dominate, and how they work, is influenced by factors including:

• the flour we use
• how much water is available
• temperature
• how often we feed it
• how much mature starter we carry over
• how long the starter stands between feeds

This also means that two starters can behave very differently even if both are fed with “equal parts”.

Why do we feed the starter?

When the microorganisms have used up much of the readily available food, activity slows down. At the same time, the starter becomes more acidic and waste products accumulate. Feeding adds fresh flour and water, dilutes the acids and gives the culture new carbohydrates to work on.

Feeding is therefore not simply a matter of adding more flour. At the same time, we decide:

• how much the mature starter is diluted
• how much new food becomes available
• how stiff or liquid the environment will be
• how long the starter will need to reach its peak

A 1:1:1 feed means one part starter, one part flour and one part water by weight. With 20 grams of starter, you add 20 grams of flour and 20 grams of water. A 1:5:5 feed means 20 grams of starter, 100 grams of flour and 100 grams of water.

The second feed provides much more fresh food relative to the amount of mature starter. At the same flour and temperature, it will therefore normally take longer to reach its peak. You can use this deliberately. A starter that needs to be ready in four hours requires a different feed from one that needs to be ready the next morning.

Why do we discard some of the starter?

We do not discard starter because the old part is “dead” or dangerous. We reduce the quantity to keep the ratio between mature starter and fresh food under control.

If you begin with 100 grams of starter and add the same amount of flour and water each time without removing anything, you have 300 grams after the first feed, 500 after the second and 700 after the third. If you continue at 1:1:1 based on the full amount, it grows even faster: 100 grams becomes 300, then 900 and then 2.7 kilograms. Before long, you need a cement mixer and a small grain store.

What we actually want is to retain a small quantity of microorganisms and give them a suitable amount of fresh flour and water. We can, for example, keep 10 grams of starter and feed it with 50 grams of flour and 50 grams of water. The rest can be discarded, but it can also be used in pancakes, waffles, crackers, pizza dough and other things where we want the flavour without relying on the starter for all the rise.

The most effective way to avoid waste is to keep a small mother starter. You do not need half a kilo of starter in the fridge. For everyday use, 20–50 grams is often plenty.

Equal parts flour and water is not a law of nature

When people say that a starter should be fed with equal parts flour and water, they normally mean equal parts by weight. That produces a starter at 100 per cent hydration: the amount of water is 100 per cent of the amount of flour.

This is practical because it is easy to calculate, easy to teach and fits many recipes. But 100 per cent hydration only tells us how much water was added relative to the flour. It does not tell us exactly what the environment is like for the microorganisms or how the starter will feel in the hand.

Different flours bind water differently. Wholemeal flour contains bran and other components that affect absorption. Rye behaves differently from white wheat flour. Two white wheat flours can also have different protein content, extraction rates and absorption.

Water activity is a measure of how much water is actually available for chemical reactions and microorganisms. It is not the same as the total amount of water. Two starters can contain the same percentage of water but still provide different environments because the flours bind that water differently.

A home baker does not need to measure water activity. The point is to understand that the figure of 100 per cent does not describe the whole starter. Consistency, type of flour, temperature, smell, acid development and the time it takes to peak tell us at least as much about how it works in practice.

Fact box: baker’s percentages

Baker’s percentages make it possible to compare doughs regardless of size. Everything is calculated as a percentage of the total flour weight, and flour is always 100 per cent.

A simple dough with 500 g flour, 350 g water and 10 g salt becomes:

• flour: 100%
• water: 70%
• salt: 2%

The water percentage is usually called the dough’s hydration. The calculation is 350 ÷ 500 × 100 = 70%.

If a recipe includes starter or levain, its flour and water must be included. The bread recipe below uses 500 g flour and 330 g water in the main dough, plus 100 g levain at 100 per cent hydration. The levain therefore contains 50 g flour and 50 g water.

The complete dough contains:

• total flour: 500 + 50 = 550 g
• total water: 330 + 50 = 380 g
• salt: 10 g

The total hydration is 380 ÷ 550 × 100 = 69.1%. The salt is 10 ÷ 550 × 100 = 1.8%. The 50 grams of flour in the levain represents about 9.1 per cent of the total flour. This is commonly called the percentage of prefermented flour.

If we divide only the water in the main dough by the flour in the main dough, we get 66 per cent. That figure looks tidy, but it does not describe the dough we are actually baking. The flour and water in the levain do not disappear when everything is mixed together.

Build the starter for the bread you want to bake

This may be the most important lesson I have learned: you do not have to force the same starter directly into every type of bread.

I distinguish between the mother starter and the baking starter, often called a levain:

• The mother starter is the small culture I maintain over time.
• The levain is built from a small amount of the mother starter, with flour, water and ripening time chosen for the bread I am going to bake.

For a light wheat loaf, I can build a levain with white wheat flour. For a coarser rye bread, I can use rye and perhaps a different consistency. If I want a mild levain, I use it while it is active and relatively young. For more acidity and a different aroma, I can adjust the temperature, stiffness, amount of mature starter and ripening time.

This does not mean that one change to one number lets you order a particular flavour. Sourdough is a living system, and the variables affect one another. It does mean that we can work deliberately instead of hoping that the same jar from the fridge suits everything.

How to make a starter from scratch

There are many methods. This one is deliberately simple and uses small quantities to limit waste.

Use a clean jar with a lid that can sit loosely on top, or can be closed without pressure building up. A straight-sided container makes it easier to see how much the starter grows. Mark the level with an elastic band or a pen.

Day 1

Mix:

• 25 g wholemeal rye flour or fine wholemeal wheat flour
• 25 g water, preferably around 25°C

Mix thoroughly, scrape down the sides and leave it somewhere warm, ideally around 22–26°C.

Day 2

You may see bubbles, or it may appear completely dead. Both are normal.

Keep 25 g of the mixture and add:

• 25 g flour
• 25 g water

Days 3–4

The starter may suddenly become very active and then appear to die. That first burst of activity is not necessarily the culture we want to bake with. A microbial succession takes place as the environment gradually becomes more acidic.

Continue with the same feed roughly once a day. If the starter clearly peaks and begins to fall well before the next feed, you can increase the ratio, for example to 1:2:2:

• 15 g starter
• 30 g flour
• 30 g water

Day 5 and onwards

When the starter regularly doubles after feeding, smells freshly acidic and repeats this over several feeds, it is beginning to become usable. The number of days depends on flour, temperature and routine. The calendar does not decide whether the starter is ready; its behaviour does.

A very new starter may raise a loaf, but it often becomes more stable after further feeds. Do not be surprised if your first loaves take longer than the recipe suggests.

Signs of a healthy starter

An active starter:

• clearly increases in volume after feeding
• has bubbles throughout, not only on top
• smells tart, fruity, yoghurt-like or lightly fermented
• reaches a peak and then begins to fall
• repeats this reasonably predictably under the same conditions

A smell of acetone or nail-polish remover often means that the starter has stood for a long time and needs feeding. On its own, it does not mean the entire culture must be discarded.

If you see fuzzy mould or clear pink, red or orange discolouration, discard the starter and clean the equipment thoroughly before starting again.

The float test, where a piece of starter is placed in water, is less reliable than many claim. Whether it floats depends on the amount of trapped gas, the flour used and how the sample is handled. An increase in volume, smell and a predictable ripening pattern are better indicators.

Temperature matters more than the clock

A recipe that tells you to ferment the dough for four hours leaves out important information if it does not say at what temperature.

A starter or dough develops much faster at 27°C than at 19°C. Times in a recipe must therefore always be treated as a guide. Watch the dough, not only the clock.

To get to know your starter, make several feeds using exactly the same quantities, flour and temperature. Write down:

• the time of feeding
• temperature
• the ratio of starter, flour and water
• when the starter has increased by 50 per cent
• when it doubles
• when it reaches its peak
• how it smells and looks

After a few rounds, you will have a far more useful timetable than you get from copying the clock of a random baker online.

Storage and maintenance

If you bake almost every day, the starter can be kept at room temperature and fed regularly. If you bake once a week or less, the fridge is easier.

A practical routine can be:

1. Keep 20–30 g mother starter in the fridge.
2. Take out 5–10 g when you are going to bake.
3. Build a levain with enough flour and water for the recipe, plus a small margin.
4. Feed the mother starter when necessary and return it to the fridge once activity has begun.

Some people always keep a little of the finished levain as their new mother starter. That also works. The important thing is that the routine makes sense, gives predictable activity and does not produce an unnecessary amount of surplus starter.

A first sourdough loaf

This is a starting point, not a universal answer. It makes one medium-sized loaf at about 69 per cent total hydration when the levain is at 100 per cent hydration.

Levain

• 20 g active mother starter
• 50 g white wheat flour
• 50 g water

Mix and leave until it has clearly grown, is full of bubbles and is close to its peak. Depending on the temperature and starter, this may take roughly 4–8 hours.

Dough

• 450 g white wheat flour
• 50 g fine wholemeal wheat flour
• 330 g water; consider holding back 20 g at first
• 100 g ripe levain
• 10 g salt

1. Mix the dough

Mix the flour with 310 g water until all the flour is hydrated. Leave for 30–60 minutes. This is often called autolyse. Then add the levain, salt and the remaining water as needed.

Do not chase the highest possible hydration in your first loaf. Flour that cannot bind the water gives a dough that is difficult to shape and poor at retaining gas. It is better to succeed at 65–70 per cent than fail at 80.

2. Bulk fermentation

Leave the dough somewhere warm in a suitable container. During the first two hours, stretch and fold it three or four times at intervals of about 30 minutes.

The first rise, often called bulk fermentation, is complete when there is clear activity, the dough feels airier and it has increased in volume. It does not always need to double. A warm dough may be ready to shape after a 30–50 per cent increase, while a cooler dough may need more time.

3. Shaping

Turn the dough gently onto the worktop. Pre-shape it lightly and leave it to rest for 15–25 minutes. Then tighten it into the desired shape without pressing out all the gas.

Place it seam-side up in a well-floured banneton, or in a bowl lined with a floured cloth.

4. Final proof

You can let the loaf finish proofing at room temperature or place it in the fridge. A cold proof makes the timetable easier and can add aroma, but fridges vary in temperature. The dough continues to develop until it is actually cold.

5. Baking

Heat the oven and a lidded Dutch oven to 250°C. The pot must be able to withstand the temperature.

Turn the loaf onto baking paper or another suitable surface, score it and carefully place it in the pot. Bake:

• 20 minutes with the lid on at 240–250°C
• then 20–25 minutes without the lid at about 220–230°C

The loaf should have good colour. Let it cool completely on a rack before cutting it. The crumb continues to set as the bread cools.

When something goes wrong

The loaf spreads flat

Possible causes:

• the dough fermented for too long
• the gluten structure is too weak
• the dough contains more water than the flour can handle
• shaping created too little tension
• the starter or levain was too weak

The loaf is dense

Possible causes:

• the starter was not active enough
• the dough was not given enough time
• the dough was too cold
• it was shaped or baked before fermentation had progressed far enough

Large holes at the top and dense dough below

This is often a sign of underproofing. Gas has gathered in a few large pockets while the rest of the dough has not developed an even structure.

The dough suddenly becomes slack and sticky

It may have gone too far. Long fermentation, high temperature and a great deal of acid can eventually weaken the gluten network. The dough may also contain too much water for the flour, or too little strength may have been developed early in the process.

The most important thing is not to follow the recipe slavishly

A good sourdough recipe gives you figures, but also teaches you what to look for.

Sourdough is affected by flour, water, temperature, time, the condition of the starter and how the dough is handled. There is therefore no single feeding ratio, hydration or proofing time that is always right.

Start simply. Keep some variables stable. Write down what you do. Change one thing at a time. Gradually, you learn the relationship between the starter, the dough and the bread.

After a few rounds, you will know roughly how long your starter takes in your kitchen, how much water your flour can handle and when the dough is fully proofed. That makes it easier to adjust the next loaf if the result was not what you had planned.

Tore

Norwegian sources and further reading

The Norwegian sources below are useful practical further reading. They do not necessarily use exactly the same method or terminology as I do in this article, which is a useful point in itself: there is more than one good way to maintain a starter and bake a loaf.

• Brød & Korn: Bak saftig bakst med surdeig – an accessible introduction to starters, fermentation and sourdough baking.
• MatPrat: Aktiv surdeigsstarter – demonstrates feeds including 1:1:1, 1:2:2 and 1:4:4, and explains how the ratio affects ripening time.
• MatPrat: Fint surdeigsbrød – a Norwegian step-by-step recipe using active starter, hydration and autolyse.
• MatPrat: Slik tar du vare på surdeigen i ferien – on storing starter in the fridge, drying it and freezing it.
• Bykjøkken: Bakerens prosenter – a practical Norwegian explanation of baker’s percentages and why the starter must be included when calculating hydration.
• Nofima: Sunnere brød med mindre salt – Norwegian research showing, among other things, that different sourdoughs and lactic acid bacteria can produce different flavour profiles.

Scientific background

• Calvert et al. (2021), A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research: https://pmc.ncbi.nlm.nih.gov/articles/PMC8117929/
• Pérez-Alvarado et al. (2022), Role of lactic acid bacteria and yeasts in sourdough fermentation: https://pmc.ncbi.nlm.nih.gov/articles/PMC9524358/
• Islam et al. (2024), Sourdough Bread Quality: Facts and Factors: https://pmc.ncbi.nlm.nih.gov/articles/PMC11241011/