Here's one for you food scientists. The other day I was making a puffed pancake recipe that calls for whole milk, egg, flour and some flavourings (lemon peel and vanilla). You put it in a skillet and pop it in the oven for 10 or 15 mins. It puffs up real nice then you fill it with fruit etc. This time when I made the pancake I had no whole milk and thought I would add buttermilk instead. Well, the thing never puffed up. So my guess is the acid in the buttermilk interfered with what the egg does to puff the thing up. Does anyone have a better more detailed explanation?