What is the purpose of baking powder in batter? In particular, what is the purpose of the baking powder in this recipe:

http://www.wearesovegan.com/korean-cauliflower-bites/
The baking powder undergoes a chemical reaction which produces small gas bubbles in the batter.  The bubbles break up the batter coating (sort of like the geometry inside a sponge) so you wind up with a mass of little holes each surrounded by a thin layer of bready material, and it all fries up airy, light and crispy; instead of one thick, dense, hard shell of cooked paste around your cauliflower bits.