Caramelized onions
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Caramelization is a process of browning of sugar used extensively in cooking for the resulting sweet nutty flavor and brown color. The brown colors are produced by three groups of polymers: caramelans (C24H36O18), caramelens (C36H50O25), and caramelins (C125H188O80). As the process occurs, volatile chemicals such as
diacetyl Diacetyl (IUPAC systematic name: butanedione or butane-2,3-dione) is an organic compound with the chemical formula (CH3CO)2. It is a yellow liquid with an intensely buttery flavor. It is a vicinal diketone (two C=O groups, side-by-side). Diacet ...
are released, producing the characteristic caramel flavor. Like the
Maillard reaction The Maillard reaction ( ; ) is a chemical reaction between Amino acid, amino acids and Reducing sugar, reducing sugars that gives browned food its distinctive flavor. Searing, Seared steaks, fried dumplings, cookies and other kinds of biscuits, b ...
, caramelization is a type of non-enzymatic browning. Unlike the
Maillard reaction The Maillard reaction ( ; ) is a chemical reaction between Amino acid, amino acids and Reducing sugar, reducing sugars that gives browned food its distinctive flavor. Searing, Seared steaks, fried dumplings, cookies and other kinds of biscuits, b ...
, caramelization is pyrolytic, as opposed to being a reaction with
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
s. When caramelization involves the
disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, la ...
sucrose, it is broken down into the
monosaccharides Monosaccharides (from Greek '' monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units ( monomers) from which all carbohydrates are built. They are usually colorless, water ...
fructose and
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
.


Process

Caramelization is a complex, poorly understood process that produces hundreds of chemical products, and includes the following types of reactions: * equilibration of anomeric and ring forms * sucrose inversion to fructose and glucose *
condensation reaction In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...
s * intramolecular bonding *
isomerization In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. Enolization is an example of isomerization, as is tautomeriz ...
of aldoses to
ketose A ketose is a monosaccharide containing one ketone group per molecule. The simplest ketose is dihydroxyacetone, which has only three carbon atoms. It is the only ketose with no optical activity. All monosaccharide ketoses are reducing sugars, be ...
s *
dehydration reaction In chemistry, a dehydration reaction is a chemical reaction that involves the loss of water from the reacting molecule or ion. Dehydration reactions are common processes, the reverse of a hydration reaction. Dehydration reactions in organic ch ...
s * fragmentation reactions * unsaturated
polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
formation


Effects of caramelization

The process is temperature-dependent. Specific sugars each have their own point at which the reactions begin to proceed readily. Impurities in the sugar, such as the molasses remaining in
brown sugar Brown sugar is unrefined or partially refined soft sugar. Brown Sugar may also refer to: Arts, entertainment, and media Films * ''Brown Sugar'' (1922 film), a 1922 British silent film directed by Fred Paul * ''Brown Sugar'' (1931 film), a 1931 ...
, greatly speed the reactions. Caramelization reactions are also sensitive to the chemical environment, and the reaction rate, or temperature at which reactions occur most readily, can be altered by controlling the level of acidity ( pH). The rate of caramelization is generally lowest at near-neutral acidity (pH around 7), and accelerated under both acidic (especially pH below 3) and basic (especially pH above 9) conditions.


Uses in food

Caramelization is used to produce several foods, including: * Caramel sauce, a sauce made with caramel * '' Confiture de lait'' and ''
Dulce de leche ''Dulce de leche'' (; pt, doce de leite), also known as caramelized milk, milk candy or milk jam in English, is a confection from Latin America prepared by slowly heating sugar and milk over a period of several hours. The resulting substance, w ...
'', caramelized, sweetened milk * Caramel candies * Creme Caramel, and the similar
crème brûlée ''Crème brûlée'' or ''crème brulée'' (; ), also known as burnt cream or Trinity cream, and virtually identical to the original crema catalana, is a dessert consisting of a rich custard base topped with a layer of hardened caramelized sugar ...
, a custard dish topped with sugar caramelized with a blowtorch * Caramelized onions, which are used in dishes like
French onion soup French onion soup (French: ''soupe à l’oignon'' ) is a soup usually based on meat stock and onions, and often served gratinéed with croutons or a larger piece of bread covered with cheese floating on top. Ancient in origin, the dish under ...
. Onions require 30 to 45 minutes of cooking to caramelize. * Caramelized potatoes * Caramelized pears *
Cola Cola is a carbonated soft drink flavored with vanilla, cinnamon, citrus oils and other flavorings. Cola became popular worldwide after the American pharmacist John Stith Pemberton invented Coca-Cola, a trademarked brand, in 1886, which was imi ...
, of which some brands use caramelized sugar in small amounts for color


See also

*
List of cooking techniques This is a list of cooking techniques commonly used in cooking and food preparation. Cooking is the art of preparing food for ingestion, commonly with the application of heat. Cooking techniques and ingredients vary widely across the world, refle ...


References


External links


Caramelization
at Science of Cooking {{Cooking Techniques Cooking techniques Culinary terminology de:Karamellisieren