Formula Help, please
I want to try the San Francisco Style Sourdough loaf from the Fresh Loaf handbook, but I'll be using Beth Hensperger's 2-week biga, which is at 74% hydration. I don't have a sourdough starter and after killing two, I'm happy enough to live without true sourdough. I would like to see what this biga will do, but I cannot wrap my head around the conversion from a 60% hydration starter. to the wetter biga.
Here's the dough formula:
White flour: 100%
Salt: 2%
Water: 72%
30% of the flour is in the starter.
and the ingredients:
White flour: 500 grams or about 4 cups
Salt: 10 grams or 1.25 tsp
Water:
- Using a wet starter: 210 grams
- Using a stiff starter: 270 grams
Starter: Two options
- Wet starter (100% hydration) 300 grams
- Stiff starter (60% hydration) 240 grams
I've tied myself in knots trying to plug the 74% biga into the recipe. Can you help?
If I like the result, is there a formula, or better yet a calculator, that I can use for other sour breads?
I'm sure there's a magical formula which will get you the answer straight away but what about us who aren't mathematicians?
So you wish for a 74% hydration biga which is 270g (is that right?). We also know that there is 500g of flour in the total recipe and 30% of that flour is in the biga. So 30% of 500g = 150g. So we take 150g from the 500g and that goes into the biga.
Now the biga needs to be 74% hydration. We know that 1g water + 1g flour = 100% hydration.
74% hydration is 74% of 150g (74/100 x 150) = 111g
So your biga is 150g flour + 111g water. Now we take the flour and water that makes up the biga off from the total flour and water.
Before the biga...
Flour 500g (100%)
Water 360g (72%)
Salt 10g (2%)
After taking off the flour and water for the biga...
Flour 350g
water 249g
Salt 10g
Biga 261g (150g flour + 111g water)
But hang on a minute... we don't get 270g for the biga. If 30% of the flour goes in the biga and you wish for it to be 74% hydration then you can't get 270g. It won't work. We can get a 270g biga at 74% hydration but it won't be 30% of the flour anymore.
But where do you get 74% hydration biga from? The recipe gives two choices non of which recommends 74% hydration. Is this where you're going wrong?
I think there's something you're miss understanding. I'll have a look at it again.
Oh! I see the confusion. My question was using about an existing biga that's at 74% hydration, rather than making a biga for this loaf. I was trying to determine how much of that biga I'd need and how to adjust the water in the dough to account for the difference.
I was thinking I could adapt this formula, but it seems not. I am new to preferments and like what a 1-2 day sponge does to my dough, so was hoping to improve on it with this 2-week model. In my total early days with bread, just over a year ago, I didn't even know there was such a thing as a biga or poolish, only sourdough and not. Since then I haven't fiddled with percentages, just done what I'm told. Followed the recipe. You can imagine my excitement, when I came across this biga. I know it won't be true sourdough, but still...
Here's a thing. As I was typing this, I looked at the formula for the dough. It is 72% hydration. Is it possible that since it's almost identical to the biga I could do a straight substitution, reducing both flour and water by 30%? Could I go even higher and use more of the biga, up to 40-50% of the final dough? Or is that not how the formulas work?
I get it now. You have a 74% hydration biga. Final question... how much biga do you have?
Here's the dough formula:
White flour: 100% Salt: 2% Water: 72% 30% of the flour is in the starter.
and the ingredients:
White flour: 500 grams or about 4 cups Salt: 10 grams or 1.25 tsp Water:
Starter: Two options
So the recipe before the biga is:
500g flour
10g salt
360g water
Take off 30% of the flour for the biga...
350g flour
10g salt
360g water
150g biga (flour minus the water)
Option 1 for a wet starter (which is 100% hydration) would be simply 150g water for the biga. Makes perfect sense...
350g flour
10g salt
*210g water
*300g biga (150g flour + 150g water)
Option 2 for a stiff starter (which is 60% hydration) would be simply 90g water for the biga. Again makes perfect sense...
350g flour
10g salt
^270g water
^240g biga (150g flour + 90g water)
Perfect. There are only two options! Not 4. It only gives you an option of a wet biga (100% hydration which is actually a poolish) or a stiff biga (60% hydration). There is no option for 74% hydration which doesn't fit into the formula.
So it gives you the flour in the biga which is 150g taken from the 500g of flour. This does not change.
Then the first two options tells you how to alter the water in the recipe to use in the biga.
The second two "options" (are the same) but is just telling you how much the biga will weigh depending on which option you choose.
Most important thing I think is the flour within the biga adds up to 150g.
So use 261g of your biga (this is the minimum you have to have for this recipe to work).
261g biga @ 74% hydration = 150g flour + 111g flour.
Now just adjust the recipe to include the biga keeping the same proportions...
350g flour
10g salt
249g water
+ 261g of your 74% hydration biga
Then proceed with your recipe as normal.
Hope this makes sense.
I don't know the full method of the recipe you're following. I would have thought that different sized bigas would mean timings have to be adjusted but the recipe allows for different sized bigas ranging from 60% hydration to 100% just keeping the flour within the biga the same. The flour within your biga adds up to the same amount and falls between the two so I imagine it'll be fine.
That is the same as I get (I don't know how much yeast is in your biga so I left that out):
Weight
I think I've got it now. Please allow me to restate it to be sure. If 30% of the flour from the recipe is in the biga, that's 30% of 500g = 150g. At 74% hydration, water from the biga is 111g. So the total weight of the biga I'll add is 261g, of which 150g is subtracted from the flour and 111g is subtracted from the water.
So in applying this to other recipes I'd do exactly the same. I'd determine the hydration of the preferment by looking at it's flour/water ratio and from that calculate how much of the flour in the dough is replaced by the flour in the preferment and follow your (very simple, thank you) math from there, using my 74% ratio (or whatever hydration level is in my chosen preferment) to determine the amounts of flour and water I need to replace?
So if a hypothetical recipe called for 400g flour + 260g water in the dough and 100g of flour + 60g of water in the preferment I'd calculate that 100g / 400g = 25% flour in the preferment. Applying these to my current biga:
100g x .74 = 74g flour from my current biga. 74g x .74 = 54.8g water from my biga.
74g + 55g = 129g of my biga goes into the dough and the final recipe for the dough is:
400g - 74g = 326g flour
260g - 55g - 205g water
129g biga
If I wanted to scale the recipe to use a different amount of flour, I could use the 25% from above to calculate the amount of flour needed in the preferment and from that how much is from my biga. If the recipe called for added yeast in the dough, I'd use the same math to determine how much yeast comes from my biga and from that how much to subtract from the yeast in the dough. OTOH, if I calculate that my biga has about the same hydration level as the preferment in the recipe, I'd add up the weight of flour and water in the preferment and use that same weight of my biga.
Is that right?
"I think I've got it now. Please allow me to restate it to be sure. If 30% of the flour from the recipe is in the biga, that's 30% of 500g = 150g. At 74% hydration, water from the biga is 111g. So the total weight of the biga I'll add is 261g, of which 150g is subtracted from the flour and 111g is subtracted from the water. think I've got it now. Please allow me to restate it to be sure. If 30% of the flour from the recipe is in the biga, that's 30% of 500g = 150g. At 74% hydration, water from the biga is 111g. So the total weight of the biga I'll add is 261g, of which 150g is subtracted from the flour and 111g is subtracted from the water".
This is 100% correct.
I'm having trouble following the rest though. But you've got the formula!
A biga is a proportion of the total flour + some of the total water prefermented. Normally a recipe will give you the method of building the biga. But you wish to use your 74% hydration biga regardless of the hydration of the biga asked for in the recipe. The flour within your biga should remain the same as is stated in the recipe and just adjust the water.
An example recipe...
Total flour 600g
Total water 390g
Salt 12g
Biga should be 40% of the flour at 65% hydration
So 40% of 600g = 240g flour
240g at 65% hydration = 156g water
So total biga is 396g but now you have to rearrange the recipe to look like this...
Flour 360g (minus the 240g in the biga)
Water 234g (minus the 156g in the biga)
Salt 12g
Biga 396g (240g flour + 156g water)
But you have a pre-prepared biga at 74% hydration (if you don't then why not just follow the recipe? But for the same of the example)...
Well the flour within the biga stays the same at 240g and 74% of 240g = 178g water (round to nearest decimal point). So the total biga you want is 418g (240g flour + 178g water. Now adjust the recipe...
Flour 360g (minus the 240g in the biga)
Water 212g (minus the 178g in the biga)
Salt 12g
Biga 418g (240g flour + 178g water)
Thanks so much, Abe, for your help. I feel much more confident now.
I look forward to seeing the bread. And should you ever wish to try sourdough again then don't hesitate to ask. Don't be put off. It's so rewarding.