Leavening agent

A leaven /ˈlɛvən/, often called a leavening agent /ˈlɛvənɪŋ/ (and also known as a raising agent), is any one of a number of substances used in doughs and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An alternative or supplement to leavening agents is mechanical action by which air is incorporated. Leavening agents can be biological or synthetic chemical compounds. The gas produced is often carbon dioxide, or occasionally hydrogen.

When a dough or batter is mixed, the starch in the flour and the water in the dough form a matrix (often supported further by proteins like gluten or polysaccharides, such as pentosans or xanthan gum). Then the starch gelatinizes and sets, leaving gas bubbles that remain.

Chemical leavens are mixtures or compounds that release gases when they react with each other, with moisture, or with heat. Most are based on a combination of acid (usually a low molecular weight organic acid) and a salt of bicarbonate (HCO3). After they act, these compounds leave behind a chemical salt. Chemical leavens are used in quick breads and cakes, as well as cookies and numerous other applications where a long biological fermentation is impractical or undesirable.

Chemical leavening were publicized by Amelia Simmons in her American Cookery, published in 1796, wherein she mentions the use of pearl ash as a leavening agent.

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(H2PO4)2). Other leavening agents developed include sodium aluminium sulfate (NaAl(SO4)2·12H2O), disodium pyrophosphate (Na2H2P2O7), and sodium aluminium phosphates (NaH14Al3(PO4)8·4H2O and Na3H15Al2(PO4)8). These compounds combine with sodium bicarbonate to give carbon dioxide in a predictable manner.

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.

This page was last edited on 1 March 2018, at 03:37.
Reference: https://en.wikipedia.org/wiki/Raising_agent under CC BY-SA license.

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