I own several bread books which I bought or received over the years. They are filled with great recipes which I barely ever make because they use yeast and I prefer to bake with a starter. I always wondered how to convert them to sourdough recipes without losing track of what the proportions of flour and water should be.
So I asked Frank, our instructor at SFBI and he explained it to us. It is not difficult really, even for mathematically challenged people like me. However and unless you are supergood at mental arithmetics (like my husband, a.k.a. the Man), it is best to have a calculator handy (and a pen and paper).
Let's take an concrete example and convert a straight dough baguette formula into a sourdough formula.
Of course we usually do not start with a formula but with a recipe. The first thing to do then is to take the weight of the flour as indicated in the recipe, decide that this weight equals 100% and then calculate the proportion of all the other ingredients compared that of the flour.
For instance, if the recipe calls for 250 g flour and 170 g water, you divide 170 by 250 and multiply the result by 100 and that will give you the percentage of the water vis-à-vis the flour. Do the same for all the other ingredients and write down the result in table format.
This method is what is called the baker's percentage where the proportion of flour always equals 100% and is used as a basis to calculate the proportions of all the other ingredients. For more info on it, click here or just google it.
Yeasted Baguette Dough Formula
| Ingredient
| Percentage
| Weight |
|---|
| Flour
| 100 %
| x
|
| Water
| 68%
| x
|
| Salt
| 2%
| x
|
| Yeast
| 0,6%
| x
|
| Total
| 170,6%
| x
|
Let's say that, in this recipe, we wish to replace the yeast by 30% of liquid starter with a 100% hydration rate, i.e. a starter which contains 100% flour and 100% water.
Starter Formula
| Ingredient
| Percentage
| Weight |
|---|
| Flour
| 100 %
| x
|
| Water
| 100%
| x
|
| Total
| 100%
| x
|
If you compare the two formulas, you can see that the percentages for flour and water are not the same. You can see also that the dough formula contains salt while the starter formula doesn't.
We know that we want 30% of starter in the final dough. Since the starter contains one part flour for one part water, it means that we are going to add 15% flour and 15% water to our dough. Right?
In other words, after the levain is added, the total flour percentage will be 115% (100% in the initial formula + 15% from the starter). It is important to keep that in mind because, as mentioned above,
the flour percentage is used to calculate the percentage of all the other ingredients.
Let's start with the salt. How much to use in our new formula?
Since we know it should be 2% of the total amount of flour, we multiply 115% (flour) by 2% and we get: 2,3%.
Now let's calculate the percentage of water. We know that, with the added starter, we will have 68% (the proportion in the initial formula) + 15% (from the starter): 68 + 15 = 83 %. But we want the hydration rate to be 68%. So we divide 83 by 100 and multiply the result by 68 and get 56,44 %, which is our new hydration rate.
Final dough formula without no specified weights
| Ingredient
| Percentage
| Weight |
|---|
| Flour
| 100 %
| x
|
| Water
| 56,44%
| x
|
| Salt
| 2,3%
| x
|
| Starter
| 30%
| x
|
| Total
| 188,74%
| x
|
So at this stage we know all the percentages we need but the only weight we know is the final dough weight, which means that right now, our new formula reads as follows:
Final dough with desired total weight
| Ingredient
| Percentage
| Weight |
|---|
| Flour
| 100 %
| x
|
| Water
| 56,44%
| x
|
| Salt
| 2,3%
| x
|
| Starter
| 30%
| x
|
| Total
| 188,74%
| 1 400 g
|
Using these indications, it is fairly easy to calculate the weight of each ingredient and I am sure most bakers can do it in their sleep. Since I am vaguely dyslexic, it isn't likely to become a second nature for me. I never remember if I should multiply or divide. I can figure it out but it is a lengthy process.
I am therefore using the following workaround (devised for me by one of my sons) which I have no trouble remembering (don't ask me why!):
To figure out the weight of any ingredient, I divide its percentage by the total percentage and I multiply the result by the total dough weight, and abracadabra ! I have the number I am looking for. Let's apply this magic trick to our formula.
Flour: 100 : 188,74 = 0,5298 x 1,400 = 741g
Water: 56,44 : 188,74 = 0,299 x 1,400 = 418g
Salt: 2,3% : 188,74 = 0,0012 x 1,400 = 17 g
Starter: 30% : 188,74 = 0,1589 x 1,400 = 222g
To check the numbers, just add up the weights:
741 + 418 + 17 + 222 = 1398 g (we don't get 1400g as I rounded up or down certain numbers but we are in the ballpark, aren't we?)
So here is the formula we need for our final dough:
Final dough
| Ingredient
| Percentage
|
| Weight |
|---|
| Flour
| 100 %
|
| 741 g
|
| Water
| 56,44%
|
| 418 g
|
| Salt
| 2,3%
|
| 17 g
|
| Starter
| 30%
|
| 222 g
|
| Total
| 188,74%
|
| 1400 g
|
It works, guys! I have successfully converted several recipes since I came back from San Francisco. Thanks, Frank!
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