While waiting for contractors to fix the power in the house yesterday, I spend some time reading the Houston Junior League Cookbook (1968) and under the hints for cooking vegetables (p216) I found "Mashed Potatoes: Add a pinch of baking powder or soda, as well as milk and butter, to make mashed potatoes light and fluffy." Has anyone done this and if so does it work?
I can not see baking soda having much of an effect as milk is not very acidic and so would not produce meaningful CO2 to add lightness to the potatoes. Using buttermilk instead of milk would produce CO2 and should have an effect.
Baking powder should produce CO2 in the milk, but I doubt the heat of the potatoes is enough to cause the second reaction.