<P> Since chemical expertise is required to create a functional chemical leaven without producing off - flavors from the chemical precursors involved, such substances are often mixed into premeasured combinations for maximum results . These are generally referred to as baking powders . Sour milk and carbonates were used in the 1800s . The breakthrough in chemical leavening agents occurred in the 1930s with the introduction of monocalcium phosphates (Ca (H PO)). Other leavening agents developed include sodium aluminium sulfate (NaAl (SO) 12H O), disodium pyrophosphate (Na H P O), and sodium aluminium phosphates (NaH Al (PO) 4H O and Na H Al (PO)). These compounds combine with sodium bicarbonate to give carbon dioxide in a predictable manner . </P> <P> Steam and air are used as leavening agents when they expand upon heating . To take advantage of this style of leavening, the baking must be done at high enough temperatures to flash the water to steam, with a batter that is capable of holding the steam in until set . This effect is typically used in popovers, Yorkshire puddings, and to a lesser extent in tempura . </P> <P> Nitrous oxide is used as a propellant in aerosol whip cream cans . Large densities of N O are dissolved in cream at high pressure . When expelled from the can, the nitrous oxide escapes emulsion instantly, creating a temporary foam in the butterfat matrix of the cream . </P> <P> Creaming is the process of beating sugar crystals and solid fat (typically butter) together in a mixer . This integrates tiny air bubbles into the mixture, since the sugar crystals physically cut through the structure of the fat . Creamed mixtures are usually further leavened by a chemical leaven like baking soda . This is often used in cookies . </P>

What are the three types of leavening agents and what is an example of each