Here’s what Dr. Yeast said about the ascorbic acid:
Ascorbic acid is not a yeast growth enhancer at all. It is a dough conditioner, but at much higher concentrations. There is only 0.3 % ascorbic acid in the yeast and please keep in mind that you are only using 1 % yeast in the dough. Therefore that amount is very low as a dough conditioner. The main reason for ascorbic acid is to prevent the oxidation of the yeast in the package. In other words: ascorbic acid extent the shelf life of the instant yeast.