Rye breads are very popular in germany and many different recipes abound. This one uses almost 50 percent rye flour with a sourdough starter to create a strong but tasty sourdough rye bread or rolls. Because some areas in the u. S. Carry only whole grain rye flour in the stores, here is a way to remove some of the bran to achieve a lighter rye bread. You could use light rye or medium rye flour with good results, too. Sourdough in the german definition is thought of mainly as the bacterial component, "Milchsurebakterien" Or lactobaccillus, and how they affect the bread dough and flavor. The wild yeast component is not studied as much and commercial yeast is added to almost every sourdough to ensure consistent rise. Rye sourdoughs rely on acetic acid and lactic acid for their flavor, while wheat sours do better with just lactic acid accumulation, which creates a milder sour taste. Not just the taste, but the way the dough reacts in the oven and its gumminess after baking is affected by the amount of acids in the dough. Acetic acid is formed in stiffer doughs (like this recipe) and at room temperature (24 c or 75 f) while lactic acid is formed in wetter doughs (100 percent hydration) and warmer temperatures (28 c or 82+ f). Because most research is performed to enhance commercial bakeries' quality, the home baker has a little more leeway. Still, a sourdough fed with rye will do better for you in a rye bread recipe and a wheat-fed sourdough in a wheat recipe. If you want to make a lot of rye sourdough bread, then try to find or start your own sourdough with rye flour. Otherwise, a traditional sourdough will do fine for a start.