Sodium aluminum phosphate and sodium aluminum sulfate are both acids that are used in baking powders. While there might be nothing wrong with the dietary aluminium in baking powders, it can give baked goods a bitter, metallic after-taste especially in recipes where subtle flavours matter. The main benefit of aluminium-free baking powder is a clean, less-bitter taste and peace-of-mind for health-conscious bakers who'd like to avoid dietary aluminium as much as possible. Note: Batters using aluminium-free baking powder must be mixed and put into the oven quickly as the leavening action that begins as soon as the powder is mixed into the batter might be lost if the batter is left sitting out too long.