tropit

I've been reading about how to make sourdough, pretzel buns for hamburgers. Some of the ingredients listed in many of the recipes are kind of odd, like, "sourdough starter discard," " non-diastatic malt powder," instant yeast (even though there is already starter,) baking soda, etc. I'm a little befuddled.

Has anyone ever made sourdough, pretzel buns before? What role do these odd ingredients play?

Thanks,