is there a simple formula for this?
I generally use about 200g of 100% hydration starter for roughly 600g flour and it mostly seems to work but I wonder what differences would occur if I used a lot less or a lot more starter.
I don't really understand the rules and if there are some general ones I would be grateful to be enlightened.
thank you.
General, and I mean really general, is the more starter, the quicker the rise. So if you want a long fermentation time to develop flavor, you can use a very low percentage of starter . The loaf I did yesterday was 12 grams of starter ( 6 flour 6 water ) to 450 grams of flour. You can also get a longer ferment by using cooler temps.
Just curious – what was your bulk time and temp for that amount of starter?
there are several factors:
Strength/activity: the stronger, more powerful, higher density of living wild yeast cells (per gram of starter), the more-active the levain, the less you need. And when I use a whole wheat starter/levain, I need less of it. Also, some strains of wild yeast just outperform others. My starter from carlsfriends.net outperformed my starter from culturesforhealth.com.
So... for consistent performance from bake to bake, the baker wants to keep the starter's feeding schedule, feeding ratio, and the ingredients used for feeding, all consistent. Consistency is more important than the details themselves. Find what fits or works for you, and stick to it.
Time: the longer you ferment the dough, the less levain you need. Less wild yeast cells doing same work over a longer time.
Temp: The higher the temp of your dough, throughout the whole process, the less levain you need. Higher temp (up to a point) makes wild yeast work faster.
As Ken Forkish says: "Time and temperature are ingredients.
Whole grain: the greater the percentage of whole grain in the dough formula, the less levain you need. Whole grain ferments faster than refined flour due to the enzymes in the bran making more sugar (from the starch) for the wild yeast.
Additives: such as diastatic malt powder, which makes sugar out of starch, boost the wild yeast's performance. Directly adding sugar, such as sucrose, dextrose, maltose (malt sugar) also directly feed and boost the wild yeast.
Same things mainly apply to commercial yeast too. Except commercial yeast in the US is all one strain, as far as I know.
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Examples: for my loaves of 90% home-milled whole wheat I use 14% starter (7% prefermented flour) for a same day bake. But only 7% starter (3.5% prefermented flour) if the bulk or final proof goes overnight.
How did I figure out my 7%/3.5% rule? Lots of trial... and... error. Lots. And taking exact notes, so that I could look back and see what result changed, in what direction, with each change of "input" or procedure/time.
And also remember that you need time for the gluten in the flour to develop with a typical higher hydration sourdough method ("no knead" or with a few stretch and folds spaced out over time).
So it is about balancing how much time you need for that, against how much time you will have before your dough is ready for the oven, and then beyond ready (which you don't want).