Question on my sourdough hydration and build calculations, double checking
Hi! I found in Jeffery Hamelman's Bread the section on "Building the Culture (also known as "Elaborating")", page 146, and while I'm pretty sure I understand it, I need some verification.
I started my rye culture, and have fed him, 1 measured cup rye flour with 1 measured cup bottled water according to the instructions given in The River Cottage Bread Handbook. What would have been, if I weighed it, 227gr water and 120gr dark rye flour.
I was happy not knowing the hydration % until I came up against it on JMonkey's post, "Lesson: Squeeze more sour from your sourdough".
He states, "The most common consistency is to have equal weights of water and flour, also known as 100% hydration because the water weight is equal to 100% of the flour weight. That’s roughly 1 scant cup of flour to about ½ cup of water. Jeffrey Hamelman keeps his at 125%, and quite a few folks keep theirs at 200% (1 cup water to 1 cup flour)."
However, when I do the math, I come up with a hydration ratio of 189:
(227g water/120g flour)x100)
Now I'm assuming that in every hydration flour is always 100 units, so therefore water would be 189 units. Isn't that a 189% hydration?
Using that number, if I do the math for creating 400g of mature stater from 30 grams of seed at the same 189% hydration, for example, according to the method described in Hamelman's Bread the calculations to figure out how much water/flour I would need to add would go like this:
- The total number of units in the 189% hydration would be 289: 100 units flour + 189 units water= 289 total units.
- I would use the formula 370/289=1.28 . That is, the 370 grams more starter needed divided by the total amount of units in the hydration.
- Then I would multiply that by the 100 units of flour, so 1.28x100=128.03 grams of flour.
- Doing the same for the water, 1.28x189= 242 grams of water (really 241.92).
So, to wrap it up, is my seed culture of 1 measured cup flour to 1 measured cup water really 189% hydration and not 200%?
And to "grow" 400 grams of mature starter from 30 grams of seed culture at my 189% hydration I would feed it 128.03 grams of flour and 242 grams of water?
My sincere apologies if this topic has been beaten to death, I really do think I understand the calculations, I just wan tto double check that how I'm interpreting the information is correct. :)
I just checked Rose Levy Berenbaum's The Bread Bible, she gives the weight of 1 cup of water as about 237 grams. The hydration formula would then be (if we use that number) 237/120=1.975, rounding up to 200. So the total units would then be 100 flour + 200 water for a total of 300 units?