I understood that there'd be occasions to use ascorbic acid in whole grain breads.  I've been searching for a reasonable local source, but have found it to be questionably dear.  When I researched online sources, I found that a crushed 250mg vitamin C tablet will do in place of 1/8 teaspoon ascorbic acid to a loaf of bread.  Great, because I have a lot of vitamin C tablets otherwise going to waste.