- Leavening agent
A leavening agent (sometimes called just leavening or leaven) is a substance used in
doughs and batters that causes a foaming action intended to lighten and soften the finished product. The leavening agent reacts with moisture, heat, acidity, or other triggers to produce gas (usually carbon dioxideand sometimes ethanol) that becomes trapped as bubbles within the dough. When a dough or batter is mixed, the starchin the flour mixes with the water in the dough to form a matrix (often supported further by proteins like glutenor other polysaccharides like pentosans or xanthan gum), then gelatinizes and "sets"; the holes left by the gas bubbles remain,
Microorganisms that release
carbon dioxideas part of their life cycle can be used to leaven products. Varieties of yeastare most often used, particularly Saccharomycesspecies (i.e. baker's yeast), though some recipes also rely on certain bacteria. Yeast leaves behind waste byproducts (particularly ethanoland some autolysisproducts) that contribute to the distinctive flavor of yeast breads. In sourdoughbreads, the flavor is further enhanced by various lactic or acetic acid bacteria.
Leavening with yeast is a process based on
fermentation, biologically changing the chemistry of the dough or batter as the yeast works. Unlike chemical leavening, which usually activates as soon as the water combines the acid and base chemicals, yeast leavening requires proofing, which allows the yeast time to reproduce and consume carbohydrates in the flour.
Yeast can also be used to make
alcoholic beverages like beer. The resulting cast-off yeast, known as barm, can be used as a leavener and was probably ancestral to the use of modern pure-cultured yeast.
While not as widely used, bacterial fermentation is sometimes used, occasionally providing a drastically changed flavor profile from a yeast fermentation;
salt rising bread, which uses a culture of the Clostridium perfringensbacterium, is a well-known example.
Some typical biological leaveners are:
* (unpasteurised - live yeast)
Chemical leaveners are chemical mixtures or compounds that typically release
carbon dioxideor other gases when they react with moisture and heat; they are almost always based on a combination of acid (usually a low molecular weight organic acid) and an alkali (though ammonia-based leaveners are also available, though in decreasing quantity). They usually leave behind a chemical salt. Chemical leaveners are used in quick breads and cakes, as well as cookies and numerous other applications where a long biological fermentation is impractical or undesirable.
Since chemical expertise is required to create a functional chemical leaven without leaving behind off-flavors from the chemical precursors involved, such substances are often mixed into premeasured combinations for maximum results. These are generally referred to as
Chemical leavening agents include:
baking soda(a.k.a., sodium bicarbonate)
* sodium aluminum phosphate (SALP)
* sodium acid pyrophosphate (SAPP)
ammonium bicarbonate(a.k.a., hartshorn, horn salt, bakers ammonia)
potassium bicarbonate(a.k.a., potash)
potassium bitartrate(a.k.a., cream of tartar)
potassium carbonate(a.k.a., pearlash)
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 leavener. This is often used in cookies.
whiskon certain liquids, notably creamor egg whites, can also create foams through mechanical action. This is the method employed in the making of sponge cakes, where an egg protein matrix produced by vigorous whipping provides almost all the structure of the finished product.
Chorleywood Bread Processuses a mix of biological and mechanical leavening to produce bread; while it is considered by food processors to be an effective way to deal with the soft wheat flours characteristic of British Isles agriculture, it is controversial due to a perceived lack of quality in the final product. The process has nevertheless been adapted by industrial bakers in other parts of the world.
Steamand airare 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 and Yorkshire puddings, and to a lesser extent in Tempura. Nitrous oxideis used as a propellant in aerosol whip cream cans. When the gas boils out of the cream, it also instantly creates a foam.
* Matz, S (1972). "Bakery Technology and Engineering", AVI Publishing Co.
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Look at other dictionaries:
leavening agent — ▪ baking substance causing expansion of doughs and batters by the release of gases within such mixtures, producing baked products with porous structure. Such agents include air, steam, yeast, baking powder, and baking soda. Leavening… … Universalium
leavening agent — noun Any organism or substance used to make baked goods rise … Wiktionary
leavening — [lev′ niŋ] n. 1. a substance used to make baked goods rise by the formation of gas, esp. carbon dioxide, in the batter or dough, as baking powder, yeast, etc.: also leavening agent 2. any influence spreading through something and working on it to … English World dictionary
leavening — noun 1. an influence that works subtly to lighten or modify something (Freq. 1) his sermons benefited from a leavening of humor • Syn: ↑leaven • Hypernyms: ↑imponderable 2. a substance used to produce fermentation in dough or a liquid … Useful english dictionary
leavening — noun Date: circa 1626 a leavening agent ; leaven … New Collegiate Dictionary
leavening — /lev euh ning/, n. 1. Also called leavening agent. a substance used to produce fermentation in dough or batter; leaven. 2. the act or process of causing to ferment by leaven. 3. leaven (def. 3). [1600 10; LEAVEN + ING1] * * * … Universalium
leavening — 1. adjective made light by aeration 2. noun a leavening agent See Also: leaven, unleavened … Wiktionary
leavening — leavÂ·enÂ·ing || levnÉªÅ‹ n. substance (such as yeast) which causes a batter or dough to ferment and rise, leaven; something that causes gradual change, something which alters or transforms leavÂ·en || levn n. substance (such as yeast) which… … English contemporary dictionary
leavening — (Roget s Thesaurus II) noun An agent that stimulates or precipitates a reaction, development, or change: catalyst, ferment, leaven, yeast. See CHANGE … English dictionary for students
raising agent — noun any substance added to a food product (such as dough or batter) that makes them rise when cooked; a leavening … Wiktionary