Stiff vs. liquid starter
Some recipes ask for liquid starter (100% hydration), others for stiff starter (50-60% hydration). But why?
If I did the same recipe twice, same ingredients, and method, once with liquid starter and once with stiff starter, same final hydration and percentage of prefermented flour - what exactly would change? Sourness? Fermentation time? Would there even be any perceivable changes in the final product in terms of flavor, oven spring etc.?
I'm just asking because I adjusted a rye sourdough loaf recipe to 100% starter so it would be easier to calculate the final amount of ingredients and dough (my Dutch oven is small, can't go much over 350 g flour).
If calculating with a 100% hydration starter is way easier and if there are no perceivable changes, why go through the hassle and work and calculate with 60% hydration starter?
Yes, this is an excellent question and one which does not have a definitive answer. I believe much of it has to do with tradition. Certain formulas call for specific preferment because that is how it has "always been done". Another reason is that many believe a stiff preferment (eg biga) will impart strength to the final dough because there is more acidity built up in the absence of water. A high-hydration preferment will theoretically add extensibility (eg poolish) because enzymes like protease are more active in the presence of water.
Others believe variations in hydration affect the flavor of the loaf. A poolish should theoretically impart a "wheaty, nutty" flavor as is appropriate for a baguette, while a biga will add a "sweeter, acidic flavor".
But at least one highly respected author I have read did experiments using all different kinds of preferment hydration levels and baked off hundreds of loaves. What he found was that none of it made any difference to the final flavor, loaf volume or crumb structure, as long as the final dough hydration was the same.
Since then, I have only used a 100% hydration preferment for all my formulas with great success. I find stiff preferments harder to make. I hope that answers your questions (at least a little).
Local Breads – Daniel Leader, page 43.
Liquid levain. This is a relatively new kind of sourdough, a batterlike culture made from wheat flour and water that is easy to mix and easy to measure out. It has gained in popularity in France because it ferments more easily and is easier to mix and measure out than stiff dough levain. Liquid levain has a fruity taste and a light, bubbly feel all over your tongue. It is mildly and immediately sour.
Stiff/dough levain. This very firm sourdough is the traditional French bread starter. It ferments very slowly, a plus for French bakers who abhor overly sour bread and want to limit the production of acids in their sourdough. In contrast to liquid levain, stiff dough levain is mild but earthy and not as light on your tongue. Its flavor is richer and darker and develops slowly in your mouth.