The single most important variable in a sourdough recipe is hydration, which is the ratio of water to flour by weight expressed as a percentage. A standard loaf is built around sixty-five to eighty percent hydration, with higher hydration generally producing a more open crumb but also being more difficult to handle. Hydration is one of many ingredient relationships that bakers describe using baker's percentage, a system in which every ingredient is expressed as a percentage of total flour weight. In this system, flour is always one hundred percent, and water, salt, starter, and any inclusions are calculated relative to it. Salt typically represents about two percent of flour weight and plays several roles: it strengthens gluten, slows yeast activity to regulate fermentation, and adds flavor.
Flour choice dramatically shapes the character of the bread. Bread flour, with twelve to fourteen percent protein, builds strong gluten and tolerates long fermentation well. All-purpose flour, at ten to twelve percent protein, is versatile and works in many recipes. Whole wheat flour is milled from the entire wheat kernel and includes the bran and germ, which produce a denser crumb, more complex flavor, and noticeably faster fermentation because the bran carries natural enzymes and minerals. Higher-extraction flour sits between whole wheat and white flour, with most of the bran sifted out, while Type 00 is a finely milled Italian flour used especially for pizza and pasta whose protein content varies. Beyond wheat, rye flour is a different grain with much less gluten and requires different handling; spelt and einkorn are ancient wheats with distinctive flavors and weaker gluten structures. Fresh-milled and stone-milled flours preserve more enzymes, oils, and nutrients than heavily processed commercial flours, and many bakers are increasingly interested in heritage wheat varieties and the field-to-loaf movement that traces grain from farm to bread.
Specialty ingredients also enter the conversation. Malt, in diastatic form, provides active enzymes that break starch into sugars that feed the yeast; non-diastatic malt simply adds flavor and color without active enzymes. Fats such as olive oil tenderize the crumb and add flavor, especially in breads like focaccia and ciabatta. Seeds and grains add texture and nutrition, but should be soaked beforehand so they do not draw moisture out of the dough during baking. Buckwheat is a pseudo-grain, technically not wheat, that is naturally gluten-free and useful in alternative baking. A few ingredients, including vital wheat gluten, vitamin C, and commercial dough conditioners, are sometimes used to strengthen dough, but they are not part of traditional artisan sourdough practice.