A German ligature that originally stood for 'sz', but can be transliterated as 'ss'. It is never found in Swiss German. It looks like a B, but sounds like an S. Compare to the boring language known as English, which only has the ligatures Ã and Å, which are rarely used.
The only other flour used in traditional pumpernickel is wheat flour, which is used as an ingredient in the sourdough starter, a pre-fermented flour, water and yeast mixture that combines with the rye flour to hold the bread together.
Cake flour is a light flour made of soft wheat flour that has been chlorinated to produce a flour with about 6-8% protein content and a beautiful texture. Cake flour is used in many cakes, cookies, and muffins when a soft texture and light, airy result is desired.