When I would read my first sourdough recipes and would come across '20% starter', I've always wondered about its hydration (often not mentioned).
What struck me at first was that did not seem to be taken into consideration in the hydration. Well, then I noticed that some bakers did it (e.g. Trevor Wilson, as far as I can tell).
But that is not my point here, since I know how to take that into consideration (using total hydration).
Say I am baking two loaves, using the exact same process, the exact same total hydration (taking starter into consideration), same total mass also.
I'd imagine that if I want both loaves to proof in the same period of time, I would like to have the same *number of cells* of the fermenting organisms.
I'm also willing to accept that to compare starters fed with 1:2:3 and 1:2:2, each should have been fed several times in this fashion and the measurement (computing the concentration) be taken at the same time in the process, say at its peak.
Has anyone any idea of how these things are related? How could I convert a 1:2:3 starter into a 1:2:2, so that my total fermentation time is the same?
I've been thinking a bit about this.
I wonder if I should then try to keep the ratio of (mass of fermenting organism) / (mass of added flour) constant across loaves. Since those organisms will have to feed on the added flour (assuming the flour in the starter had pretty much been depleted of nutrients), this might be the most important actor in the total fermentation time. So, if I had a formula such as
O = c x S
to compute the mass O of the organisms in terms of the mass of starter S, keeping O constant acroos loaves 1 and 2 would mean that the percentage of starter i1, i2 would satisfy
i2 = (c1/c2) x i1
With that at hand, I could compute the added flour, water and starter of loaf 2 and even keep the total dough mass and final hydration constant.
I think this is what I am asking. Does anybody have an idea of how these coefficients c behave? Or at least a rough estimate for a ratio such as c1/c2 for typical feeding routines (say, 1:2:3 vs. 1:1:1)?
I can't answer your question about % starter and fermentation time. However, here are some other considerations.
1. The "mass" of organisms is not exactly the same as their metabolic activity level. Temperature of fermentation/proofing and dough hydration are also important factors in timing. Also minerals present from whole grain flours are important factors.
2. The best way of expressing the amount of starter in a recipe is the percentage of the flour that is pre-fermented, i.e., in the starter, along with the starter's hydration.
3. Decisions about the amount of starter to use are generally based on the desired flavor of the bread and dough characteristics, e.g., extensibility, not the fermentation time per se.
David
Ok, David.
Thanks for the reply. I guess this is not an issue that interests many people.
Maybe the technical way I asked it turned some people off (basically everyone).
While I do have a curiosity about that, I'd settle for knowing how to adapt a recipe with 20% of a starter hydrated at 67% to use with a starter with 100% hydration. In a Brazilian forum, someone answered that if he switches from a 67% to a 100%, he'd usually take off 5 percentage points of the recipe (so, he'd use 15% of the 100% starter in the new recipe).
But I guess your answer is more along the lines that this is not a reasonable question and that one would use one or another starter depending on things such as taste. Fair enough.
I've been using a 67% starter, but when I decided to leave flour, water and salt overnight in the fridge and added the starter the following day, I decided that a 100% starter would be easier to work with. The next time I tried this method, I used it and it was indeed much easier. But I just kept the same numbers and was wondering if this is really makes sense.
If you prefer a more "technical" approach to starter conversion, here is a tutorial:
Converting starter hydrations: A Tutorial. Or through thick and thin and vice versa
I still don't have an answer to your question about fermentation time.
Happy baking!
David
Thank you once again. I'll check it out. See you around here, maybe somewhere else in the forum.