Baking Powder Baking powders are mixtures of dry acid or acid salts and baking soda, with starch or flour added to standardize and help stabilize the mixtures. I use Rumford baking powder, an all-phosphate product containing calcium acid phosphate that is found in most supermarkets or health food stores. It lacks the bitter aftertaste associated with SAS baking powders, which contain sodium aluminum sulfate. (The supposed advantage of SAS powders is that they release a little more carbon dioxide during the baking stage than during the mixing stage, but I find I can interchange equal volume and weight of either type of baking powder.)
