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.
For general baking: Replace up to 1/4 of any wheat flour in a recipe or substitute 5/8 cup potato flour for 1 cup all-purpose flour. For yeast breads: Replace up to 1/6 of the wheat flour in a bread recipe or substitute 5/8 cup potato flour for each cup of all-purpose flour..