Hi, Is there a rule of thumb on how much natural yeast, as opposed to dried, to use per lb of flour ?
It depends on your recipe’s yeast percentage. In terms of weight... Use 3 times more fresh yeast as dried.
Most bread formulas call for a compressed yeast level of 2% of the flour weight.This would amount to 0.32 oz. (9 grams) of compressed yeast for every lb. of flour.
Yeast per pound of flour depends on your recipe and formula.
The conversion of fresh yeast to active dry and instant yeast is probably what you need to know.
For each ounce of fresh yeast use 0.4 of active dry yeast (dissolved in water)
For each ounce of fresh yeast use 0.33 ounce of instant dry yeast.
For a rule of thumb for natural (wild yeast) from commercial dry yeast. That is a bit more tricky. There are conversion tables all over the internet for commercial yeast conversions. This is what has be been working for me. Please note your results may vary. My results are purely anecdotal and specific to my culture and conditions. However it is a good starting point. The Will Falzon method/Roadside Pie King method: Use 15% of the total flour weigh of 100% hydration mature/ripe starter. That would correlate to 7.5% prefermented flour. Additionally, you would need to deduct the water & flour in the starter from the formula flour and water ( to keep the original hydration.) It works for me! Sourdough Turmeric bread. Original Pie King formula.