A leavening agent (also leavening or leaven, pronounced /ˈlɛvənɪŋ/, /ˈlɛvən/) is any one of a number of substances used in doughs Dough is a paste made out of any cereals or leguminous crops by mixing flour with a small amount of water and/or other liquid. This process is a precursor to making a wide variety of foodstuffs, particularly breads and bread-based items (e.g., dumplings), including flatbreads, and pancakes, noodles, crusts, pastry, and similar items. This includes and batters Batter is a liquid mixture, usually based on one or more flours combined with liquids such as water, milk or eggs. Beer is a common component. Often a leavening agent is included to aerate and fluff up the batter as it cooks, or the mixture may be naturally fermented for this purpose as well as to add flavour that cause a foaming action which lightens and softens the finished product. The leavening agent incorporates gas bubbles into the dough—this may be air incorporated by mechanical means, but usually it is carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere produced by biological agents, or by chemical agents reacting with moisture, heat, acidity, or other triggers. When a dough or batter is mixed, the starch Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store. It is the most important carbohydrate in the human diet and is contained in such staple foods as potatoes, wheat, maize , rice, and cassava in the flour mixes with the water in the dough to form a matrix (often supported further by proteins like gluten Gluten is the composite of two proteins called gliadin and glutenin. These exist, conjoined with starch, in the endosperm of some grass-related grains, notably wheat, rye, and barley. Gliadin and glutenin comprise about 80% of the protein contained in wheat seed. Being insoluble in water, they can be purified by washing away the associated starch or other polysaccharides like pentosans They either have an aldehyde functional group in position 1 , or a ketone functional group in position 2 (ketopentoses) or xanthan gum Xanthan gum is a polysaccharide used as a food additive and rheology modifier . It is produced by fermentation of glucose or sucrose by the Xanthomonas campestris bacterium), then gelatinizes and "sets"; the holes left by the gas bubbles remain.
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Biological leaveners
Main article: Yeast Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with the 1,500 species currently described estimated to be only 1% of all yeast species. Most reproduce asexually by budding, although a few do so by binary fission. Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation ofMicroorganisms that release carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere as part of their life cycle can be used to leaven products. Varieties of yeast Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with the 1,500 species currently described estimated to be only 1% of all yeast species. Most reproduce asexually by budding, although a few do so by binary fission. Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation of are most often used, particularly Saccharomyces Saccharomyces is a genus in the kingdom of fungi that includes many species of yeast. Saccharomyces is from Greek σάκχαρ and μύκης (mushroom) and means sugar fungus. Many members of this genus are considered very important in food production. One example is Saccharomyces cerevisiae, which is used in making wine, bread, and beer. Other species (such as baker's yeast Baker's yeast is the common name for the strains of yeast commonly used as a leavening agent in baking bread and bakery products, where it converts the fermentable sugars present in the dough into carbon dioxide and ethanol. Baker's yeast is also called Saccharomyces cerevisiae, which is the same species commonly used in alcoholic fermentation,, Saccharomyces cerevisiae Saccharomyces cerevisiae is a species of budding yeast. It is perhaps the most useful yeast owing to its use since ancient times in baking and brewing. It is believed that it was originally isolated from the skins of grapes . It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like Escherichia), though some recipes also rely on certain bacteria The bacteria ( [bækˈtɪəriə] ; singular: bacterium)[α] are a large group of single-celled, prokaryote microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste,. Yeast leaves behind waste byproducts (particularly ethanol Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a powerful psychoactive drug and one of the oldest recreational drugs. It is best known as the type of alcohol found in alcoholic beverages and thermometers. In common usage, it is often referred to simply as and some autolysis In biology, autolysis, more commonly known as self-digestion, refers to the destruction of a cell through the action of its own enzymes. It may also refer to the digestion of an enzyme by another molecule of the same enzyme. The term derives from the Greek words αυτό and λύσις ("splitting") products) that contribute to the distinctive flavor of yeast breads. In sourdough Sourdough is a dough containing a lactobacillus culture, usually in symbiotic combination with yeasts. It is one of two principal means of leavening in bread baking, along with the use of cultivated forms of yeast . It is of particular importance in baking rye-based breads, where yeast does not produce comparable results. In comparison with yeast- breads, the flavor is further enhanced by various lactic acid bacteria The Lactic Acid Bacteria comprise a clade of Gram-positive, low-G (lactobacilli Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic bacteria.[unreliable source?] They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign. In humans they are present in the vagina and the) or acetic acid bacteria Acetic acid bacteria are bacteria that derive their energy from the oxidation of ethanol to acetic acid during respiration. They are Gram-negative, aerobic, rod-shaped bacteria (acetobacilli Acetobacter is a genus of acetic acid bacteria characterized by the ability to convert ethanol to acetic acid in the presence of oxygen. There are several species within this genus, and there are other bacteria capable of forming acetic acid under various conditions; but all of the Acetobacter are known by this characteristic ability).
Leavening with yeast is a process based on fermentation Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. A more restricted definition of fermentation is the chemical conversion of sugars into ethanol. The science of fermentation is known as zymology, 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 Proofing , as the term is used by professional bakers, is the final dough-rise step before baking, and refers to a specific rest period within the more generalized process known as fermentation. Fermentation is a step in creating yeast breads and baked goods where the yeast is allowed to leaven the dough, which allows the yeast time to reproduce and consume carbohydrates in the flour.
Yeast can also be used to make alcoholic beverages An alcoholic beverage is a drink containing ethanol . Alcoholic beverages are divided into three general classes: beers, wines, and spirits like beer Beer is the world's most widely consumed and probably the oldest of alcoholic beverages; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from cereal grains—most commonly malted barley, although wheat, maize , and rice are widely used. Most beer is or wine Wine is an alcoholic beverage, typically made of fermented grape juice. The natural chemical balance of grapes is such that they can ferment without the addition of sugars, acids, enzymes or other nutrients. Wine is produced by fermenting crushed grapes using various types of yeast. Yeast consumes the sugars found in the grapes and converts them. The resulting cast-off yeast, known as barm Barm is the foam, or scum, formed on the top of liquor when fermenting. It was used to leaven bread, or set up fermentation in a new batch of liquor. Barm, as a leaven, has also been made from ground millet combined with must out of wine-tubs and is sometimes used in English baking as a synonym for a natural leaven. Various cultures derived from, can be used as a leavener and was probably ancestral to the use of modern pure-cultured yeast.
While not as widely known, bacterial fermentation is sometimes used, occasionally providing a drastically changed flavor profile from a yeast fermentation; a well-known example is salt rising bread Salt rising bread is bread in which the main rising agent is a bacterium Clostridium perfringens , which leavens the bread along with lactobacillus and other wild microbes, as opposed to mainly yeast or baking soda. It is thought that the salt used in the starter is used to suppress yeast growth and provide an environment more conducive to the C, which uses a culture of the Clostridium perfringens Clostridium perfringens is a Gram-positive, rod-shaped, anaerobic, spore-forming bacterium of the genus Clostridium. C. perfringens is ubiquitous in nature and can be found as a normal component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates, insects, and soil bacterium.
Some typical biological leaveners are:
- beer Beer is the world's most widely consumed and probably the oldest of alcoholic beverages; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from cereal grains—most commonly malted barley, although wheat, maize , and rice are widely used. Most beer is (unpasteurised—live yeast)
- buttermilk Buttermilk refers to a number of dairy drinks. Originally, buttermilk was the liquid left behind after churning butter out of cream. It also refers to a range of fermented milk drinks, common in warm climates where fresh milk would otherwise sour quickly. It is also popular in Scandinavia and the Netherlands, despite the colder climates
- ginger beer Ginger beer is a carbonated drink that is flavoured primarily with ginger and sweetened with sugar or artificial sweeteners. Most ginger beer produced commercially is a manufactured soft drink. The original version, rarely produced commercially since the mid-twentieth century but often home brewed, is a brewed alcoholic beverage
- kefir Kefir , purportedly from either the Turkish "keyif" (joy/pleasure) or "köpür" ((milk) froth, foam), is a fermented milk drink that originated with shepherds of the Caucasus region, who discovered that fresh milk carried in leather pouches would occasionally ferment into an effervescent beverage. It is prepared by inoculating
- sourdough starter
- yeast Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with the 1,500 species currently described estimated to be only 1% of all yeast species. Most reproduce asexually by budding, although a few do so by binary fission. Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation of
- yogurt Yoghurt or yogurt is a dairy product produced by bacterial fermentation of milk. Fermentation of lactose produces lactic acid, which acts on milk protein to give yoghurt its texture and its characteristic tang. Dairy yoghurt is produced using a culture of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus
Chemical leaveners
Chemical leaveners are chemical mixtures or compounds that release gases (usually carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere) 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; these leave behind a chemical salt In chemistry, salts are ionic compounds that can result from the neutralization reaction of an acid and a base. Salts are ionic compounds composed of cations and anions (negative ions) so that the product is electrically neutral (without a net charge). These component ions can be inorganic such as chloride (Cl−), as well as organic such as. Chemical leaveners are used in quick breads A quick bread is a type of bread which is leavened with chemical leaveners such as baking powder, sodium bicarbonate, or cream of tartar. Unlike yeast breads which often take hours to rise and can vary greatly based on external factors such as temperature, breads made with chemical leaveners are relatively uniform, reliable, and quick. Quick and cakes, as well as cookies In the United States and Canada, a cookie is a small, flat-baked treat, usually containing fat, flour, eggs and sugar. In most English-speaking countries outside North America, the most common word for this is biscuit; in many regions both terms are used, while in others the two words have different meanings—a cookie is a plain bun in Scotland, and numerous other applications where a long biological fermentation is impractical or undesirable.
Chemical leavening was first publicized by Amelia Simmons in her American Cookery[1], 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 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 baking powders Baking powder is a dry chemical raising agent used to increase the volume and lighten the texture of baked goods such as muffins, cakes, scones and North American biscuits. Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in the wet mixture to expand and thus leavening the.
Chemical leavening agents include:
- baking powder Baking powder is a dry chemical raising agent used to increase the volume and lighten the texture of baked goods such as muffins, cakes, scones and North American biscuits. Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in the wet mixture to expand and thus leavening the
- baking soda Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula NaHCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . It is a component of the mineral natron and is found dissolved in many mineral (sodium bicarbonate Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula NaHCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . It is a component of the mineral natron and is found dissolved in many mineral)
- monocalcium phosphate
- sodium aluminum phosphate (SALP)
- sodium acid pyrophosphate (SAPP)
- other phosphates A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in agriculture and industry. At elevated temperatures
- ammonium bicarbonate Ammonium bicarbonate, a compound with formula NH4(COHO), also called bicarbonate of ammonia, ammonium hydrogen carbonate, hartshorn, or powdered baking ammonia, is the bicarbonate salt of ammonia (hartshorn, horn salt, bakers ammonia Ammonia is a compound of nitrogen and hydrogen with the formula NH3. It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of)
- potassium bicarbonate Potassium bicarbonate , is a colorless, odorless, slightly basic, salty substance. According to The US Food and Drug Administration (FDA), potassium bicarbonate is "generally recognized as safe" (potash Potash is the common name for potassium carbonate and various mined and manufactured salts that contain the element potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains)
- potassium bitartrate (cream of tartar)
- potassium carbonate Potassium carbonate is a white salt, soluble in water (insoluble in alcohol), which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid. Potassium carbonate is used in the production of soap and glass (pearlash)
- hydrogen peroxide Hydrogen peroxide is naturally produced in organisms as a by-product of oxidative metabolism. Nearly all living things possess enzymes known as peroxidases, which harmlessly and catalytically decompose low concentrations of hydrogen peroxide to water and oxygen
Mechanical leavening
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.
Using a whisk on certain liquids, notably cream or 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.
The Chorleywood Bread Process uses 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.
Other leaveners
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.
Nitrous oxide is used as a propellant in aerosol whip cream cans. Large densities of N2O 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.
See also
References
- ^ Simmons, Amelia; Mary Tolford Wilson (1984) [1958]. The First American Cookbook (1984 reprint ed.). Mineola, NY: Dover. ISBN 0-486-24710-4.
- Matz, S (1972). "Bakery Technology and Engineering", AVI Publishing Co.
External links
- Wikibooks Cookbook has a recipe/module on Leavening agent
Categories: Leavening agents | Fermentation (food)
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Sat, 13 Mar 2010 19:17:46 GM
The rustic bread is much like Australia's damper and originated around the mid to late 19th Century when bicarbonate of soda was first used as a . leavening agent. . It was no wonder that soda bread was so popular. ...
