Converting a Commercial Yeast Recipe to Sourdough

An experiment in making a sourdough version of
Tiger Loaf aka Marco Polo, Giraffe or Dutch Crunch Bread.

Most of us have our own favoured breads or other leavened baked goods. These days they are generally baked using commercial yeast and the most readily available recipes use a commercial yeast process; sourdough versions can be far more difficult to find.

Attitudes are changing

More recently, for one reason or another, perhaps health, more flavourful bakes, or simply a yearning to get back to ‘the old ways’, an increasing number of people want to enjoy those same baked goodies without the use of commercial yeast.  More are baking at home, and there are artisan bakeries springing up all over the place.

The good news is, with a little work and some trial and error, you can convert any recipe which uses commercial yeast into one which only uses wild leaven – aka your own sourdough starter.

The Unpredictability Challenges

The exact commercial yeast to sourdough starter conversion ratios seems to vary – entirely unsurprising when you factor in that starter strengths and environmental conditions can vary greatly.  This is probably why commercial dried and fresh yeast became so widely used in the first place – they are far more predictable and stable as far as working out timings and therefore achieve more consistent results.  But let’s face it, that’s what we all love about baking with sourdough, the unpredictability, the fact that the results depend on range of factors including how strong and healthy our starter is, and how well we can change and adapt the process on almost every bake to contend with changes in temperature, flour and water, time restrictions, and more.

With all of this in mind, I embarked on trying to recreate that old supermarket favourite — the Tiger Loaf aka Marco Polo, Dutch Crunch or Giraffe Bread— taking a yeasted recipe and converting it to a sourdough recipe.

This is the Original Commercial Yeast Recipe (60% hydration):


Bread Dough
– 500 g Strong White Bread Flour
– 7 g Dry Instant Yeast
– 1½ tsp Golden Caster Sugar
– 1½ tsp Salt
– 15g/1 tbsp room temperature butter
– 300 ml warm water (225ml cold, 75ml boiling)

Paste Topping
– 2 tsp yeast
– 90 ml warm water (60ml cold + 30ml boiling)
– 1.5 tsp sugar
– 2 tsp toasted sesame seed oil
– 75g rice flour


  1. Mix flour, yeast, sugar and salt in a big bowl. Use fingertips to rub in the butter until it resembles fine breadcrumbs.  Mix in the water with a knife.
  2. Tip dough onto a lightly flour-dusted surface and knead for 10 minutes (or use the dough hook attachment on your mixer)
  3. Lightly oil your mixing bowl and place the dough in it and cover the bowl with a clean tea towel. Leave to rise until almost doubled in size.
  4. Once risen, gently kneading the dough just 5 times. Shape into a smooth oval and sit on a floured baking sheet.
  5. Cover the dough with a clean tea towel and leave to prove until almost doubled in size again.
  6. Preheat your oven to 200°C (fan 180°C, gas mark 6). Whisk all of the topping ingredients together until smooth. Leave this to rest for 10 minutes.
  7. Spread the paste all over the top and sides of your loaf with a palette knife
  8. Bake for 35 minutes, until golden brown and crackled. When you tap the base it sounds hollow.
  9. Cool on a wire rack.

The Conversion

Two things to keep in mind:

  1. It’s important to remember that if you substitute Starter for commercial yeast, you must also alter the flour and water quantities in the recipe in order that the recipes hydration remains the same.  Having a Starter @100% hydration makes this calculation easier.
  2. The whole baking process must change to accommodate the longer fermentation times. Basically, follow the usual sourdough process: mix, stretch and folds, bulk ferment, second prove, bake.

These are the generally accepted conversions:

Fresh Yeast
100 grams 1 sachet /5-7gms/1.25-1.5 tsp 12 – 15 grams

Using this basic conversion theory, I substituted the 7gms of commercial yeast for 100g sourdough starter @100% hydration, an inoculation of 20% in Baker’s percentages, and then made the changes to the flour and water quantities in the basic recipe.

By adding 100 g of Starter (made of 50ml of water and 50g of flour) I needed to deduct 50g of flour and 50ml of water from the original quantities in the recipe, so keeping the dough hydration level the same.  So, the recipe changed as follows, note that the hydration has remained the same.
Start of a new sourdough Bread Dough recipe  (60% hydration):
450g Strong White Bread Flour
– 7gms Dry Instant Yeast
– 100 g Active 100% hydration starter
– 1½ tsp Golden Caster Sugar
– 1½ tsp Salt
– 15g/1tbsp Butter (softened)
250 ml warm water (225ml cold, 75ml boiling)

20% starter is a fairly standard starter ratio, but if you wanted to do a longer prove or extend the process you can reduce the amount of starter; just remember to make the corresponding changes in the recipe flour and water quantities.

As always, the important thing is to WATCH YOUR DOUGH throughout the process, and only use the timings as a rough guide.

For the topping, I don’t think I swapped in enough starter for my original experiment, I only used 2  tsp. The bowl in the left one is the original commercial yeast topping recipe, the one on the right used starter and was slightly thinner consistency. The sourdough one resulted in the very light golden crust, I have adapted the recipe to having more starter so will see how this goes on the next try. Adjust the water to suit, you may not even need it as the starter may have enough, basically the topping should be a fairly thick, but spreadable paste.

Paste Topping
– 2 tsp yeast
– 85 g starter
– 1.5 tsp sugar
– 2 tsp toasted sesame seed oil
– 75g rice flour

As I mentioned above, any conversion recipe will involve some trial and error, but it is all good fun and you are developing a whole new recipe exactly to your own taste and which you can share and continue to use for years to come. The more conversions you do, the better you will get at it.

Check out the final Sourdough Tiger Loaf recipe and give it a try for yourself.

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2 thoughts on “Converting a Commercial Yeast Recipe to Sourdough”

  1. Thanks Karen for the conversion. We used to have numerous bakeries in Western New York which carried this “yeasted” version under the name of Alligator Bread and when baked in an oval baker it looked like the back of an Alligator. No longer available unfortunately.

    Will have to try the SD version. Currently I am having a ball with Wild Yeast Water which give us similar SD characteristics but without the sour taste. This will be my next bake.

    1. Thanks for the comments, Mike, please do let us know how you get on with the Alligator bread. I am with you on the Wild yeast water, I love seeing how different ones work. I use them more during the summer and use my main rye sourdough starter during the winter.

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Disclaimer: Whilst we hope the information provided is helpful and informative, we cannot guarantee that all details will be 100% accurate.  There are many schools of thought and conflicting ideas on many of the sourdough processes and methods.  This site is simply meant as a broad guide to baking sourdough, and is not a scientific reference.

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A special sharp knife, or tool which holds a razor blade, in a curved or straight manner. You use it to score the dough before baking.

Dutch Oven

A Dutch Oven is generally understood to be a covered earthenware or cast-iron container for cooking casseroles. They are ideal for bread as they can accommodate bread dough and be covered to help generate the steamy environment requiredto encourage the dough to rise. Enamel roasters with a lid, covered pyrex dishes, or even a flat tray with a bowl over the top of the dough, are equally effective.

Bakers’ Percentages

Sometimes called baker’s math, this is a method to express the different ingredients as a percentage of the total amount of flour. It makes scaling a recipe or building a recipe very easy once you know the total weight of the flour, and also allows you to know the ‘hydration’ of your dough.

Example: If you build your dough with 1000 gram flour, 670-grams water, 20-gram salt, and 8-gram yeast. According to bakers percentages, that will be 100% flour (the amount of flour is always 100%), 67% water, 2% salt, and 0.8% yeast.
You divide the amount of the different ingredients with the amount of flour.

Banneton / Brotform / Proofing Basket

A type of basket or container used to provide structure for shaped loaves of bread during proofing. Banneton baskets are also known as ‘Brotform’ or ‘proofing baskets’. It is normally used for doughs that are too soft or wet to maintain their shape while rising. They come in a range of sizes and shapes. Look for ones that fit the size of loaves you want to bake.

They are often made of natural rattan, or wood fiber. You can also use any container lined with a well-floured tea towel.

Oven Spring

The final burst of expansion of dough upon being introduced to a hot oven and where the yeast activity is increased during the first few minutes. At approximately 60C/140ºF degrees the yeast is killed off, but up until that point, dough can expand in the oven in the first phase of baking if it’s not over-fermented and still has dough strength. Many factors can impact oven spring including the length of fermentation, gluten development, and the hydration of the dough.


An alternative to traditional kneading used to develop gluten. The process is performed periodically in the bowl throughout the bulk fermentation. Take a side of the dough and gently stretch it up and over, to fold it upon itself, rotate the dough 90º, and repeat, then turn the bowl 45º and the same stretch and fold. Once all four corners of the dough have been stretched and folded, gluten development and a smooth, elastic dough are underway. Also, see ‘Folding’ and ‘Coil Folds’.

Bulk Ferment

Most loaves have two fermenting cycles. One before and one after the loaves are formed. Bulk fermentation is the first cycle, with a long fermentation period of the dough after the initial mixing of flour, water, starter, and salt and often comes during and after a period of kneading or ‘stretch and folds’.During this stage we are aiming to create dough strength, structure and flavor. The dough should feel alive, strong, airy, spongy and the surface shouldn’t feel sticky.

The bulk fermentation generally takes place at room temperature, unless otherwise noted in the recipe and is a longer period of time (4 -12 hours) than the final proofing period. This step may be referred to as the first prove or first rising. Acetic acid, an organic acid is produced by bacteria in the sourdough culture during the fermentation process. The presence of acetic acid helps to gives sourdough its characteristic acidic tang. The warmer the environment, the faster the development of the dough will be

Window Pane

The window pane test is one of the best ways to tell if you’ve sufficiently stretched and folded your bread dough. Pull a small piece of the dough and using both hands and your fingers stretch the dough very thin if it holds its shape without tearing the gluten is well-developed and your dough is ready to be pre-shaped, shaped and rest for it’s final prove.

Starter / Starter Culture / Sourdough Starter

A mixture of flour and water used to leaven bread that contains bacteria, yeast, and organic acids. Made either by inoculating with an established colony of bacteria or by capturing wild bacteria and yeasts over a longer period. Sometimes also called Leaven / Levain.



Autolyse (pronounced auto-lees) is a process in which a portion of (or total) water and flour in a bread recipe are gently pre-blended and set to rest for a period of time.

This resting period gives the dough special processing characteristics and improves the overall quality of the baked goods.

During autolyse process, several events can occur in the pre-mixed water/flour mixture:

  1. Continued flour hydration. Water molecules work their way into damaged starch, intact starch granules and proteins.
  2. Protein bonds continue to develop as a consequence of adding water, creating more gluten strands without mechanical work. This leads to better gluten structure and gas retention.
  3. Flour enzymes (mainly proteases) acquire time to adapt and work on the gluten by breaking down protein bonds.Protease activity is higher at low pH (acidic conditions). This is why autolysed doughs that contain yeast or pre-ferments (e.g. poolish) often experience greater protease activity. Such doughs are more extensible, weaker, softer and show less resistance to deformation than autolyzed non-fermented doughs.2
  4. Finally, as a result, the dough feels less sticky and very smooth after the autolyse.

As a general rule, the longer the autolyse time:

  • The shorter the dough mixing time (less mechanical development of gluten-forming proteins in needed). This means less energy consumption during mixing.
  • The shorter the dough stability duration
  • The less tolerance to overmixing. Breakdown is more pronounced once peak (maximum strength) is attained.
  • The smaller the P value in the alveograph test
  • The more extensible and less elastic the dough becomes at the end of autolysis
  • The better the sheetability and machining of dough during lamination of croissants
  • The easier and faster the dough expands during oven spring (better volume)
  • The lower the need for dough conditioners
  • The better the flavor and aroma of the finished product
Leaven/Levain/Sourdough Starter
  1. A substance, in this case a wild yeast starter, that is used in sourdough baking to make dough rise.
  2. Some methods of baking, such as ‘Tartine Method’ require a sourdough leavening agent be made from a sourdough ‘mother culture’ (aka your Starter). This technique is often employed to boost the yeast activity of the sourdough starter by feeding a small amount of starter a larger quantity of flour and water. For instance, if a recipe calls for 1 cup of sourdough starter, a leaven can be prepared 8-12 hours before the dough will be mixed by combining 1 Tablespoon of sourdough starter with ½ cup flour and a scant ½ cup of water. This leaven can then be used as the sourdough starter and will be quite active come baking time.
  1. cause (dough or bread) to rise by adding leaven.