Corn syrup
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Corn syrup is a syrup, made using cornstarch as a feedstock, and composed mainly of glucose. Formerly, corn syrup was produced by combining corn starch with dilute hydrochloric acid and then heating the mixture under pressure. Currently, corn syrup is mainly produced by first adding the enzyme α-amylase to a mixture of corn starch and water. α-amylase is secreted by various species of the bacterium Bacillus; the enzyme is isolated from the liquid in which the bacteria are grown. The enzyme breaks the starch into oligosaccharides, which are then broken into glucose molecules by adding the enzyme glucoamylase, known also as "γ-amylase". Glucoamylase is secreted by various species of the fungus Aspergillus; the enzyme is isolated from the liquid in which the fungus is grown. The glucose can then be transformed into fructose by passing the glucose through a column that is loaded with the enzyme D-xylose isomerase, an enzyme that is isolated from the growth medium of any of several bacteria.[1][2] Its major uses in commercially-prepared foods are as a thickener, sweetener, and for its moisture-retaining (humectant) properties which keep foods moist and help to maintain freshness.[3]
Corn syrup is used to soften texture, add volume, prohibit crystallization and enhance flavour. Because cane sugar quotas raise the price of sugar in the United States,[4] domestically produced corn syrup and high-fructose corn syrup are a less expensive alternative often used in American-made processed and mass-produced foods, candies, soft drinks and fruit drinks to help control cost.[3]
The more general term glucose syrup is often used synonymously with corn syrup, since the former is most commonly made from corn starch.[5] Technically, glucose syrup is any liquid starch hydrolysate of mono-, di-, and higher-saccharides and can be made from any sources of starch; wheat, rice and potatoes are the most common sources.[6]
Glucose or dextrose syrup is produced from number 2 yellow dent corn. When wet milled, approximately 2.3 litres of corn is required to yield an average of 947g of starch, to produce 1 kg of glucose or dextrose syrup. A bushel (25 kg) of corn will yield an average of 31.5 pounds of starch, which in turn will yield about 33.3 pounds of syrup. Thus, it takes about 2,300 litres of corn to produce a tonne of glucose syrup, or 60 bushels (1524 kg) of corn to produce one short ton.[7]
The viscosity and sweetness of the syrup depends on the extent to which the hydrolysis reaction has been carried out. To distinguish different grades of syrup, they are rated according to their dextrose equivalent (DE).
Glucose syrup was the primary corn sweetener in the United States prior to the expansion of High-fructose corn syrup (HFCS) production. HFCS is a variant in which other enzymes are used to convert some of the glucose into fructose. The resulting syrup is sweeter and more soluble. Corn syrup is also available as a retail product. The most popular retail corn syrup product in the United States is Karo, a fructose/glucose syrup.[8] Karo is a brand of thick corn syrup made from a concentrated solution of dextrose. The dark Karo also uses other sugars derived from corn starch with preservatives and flavorings. The light variety contains only salt and vanilla, in addition to corn syrup. It is a staple of Southern United States cuisine, e.g., to make pecan pie, and is pronounced "KAY-row" in that region.
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[edit] References
- ^ "The use of enzymes in starch hydrolysis". http://www.lsbu.ac.uk/biology/enztech/starch.html. Retrieved January, 2010.
- ^ "Enzymatic starch hydrolysis: background". http://www.bpe.wur.nl/UK/Research/Dissertations/Enzymatic+starch+hydrolysis/Enzymatic+starch+hydrolysis+background/. Retrieved January, 2010.
- ^ a b Knehr, Elaine. "Carbohydrate Sweeteners". Virgo Publishing. http://www.foodproductdesign.com/articles/2005/05/carbohydrate-sweeteners.aspx. Retrieved 2008-10-17.
- ^ "U.S. Sugar Import Program". USDA. http://www.fas.usda.gov/itp/imports/ussugar.asp. Retrieved 2009-03-21.
- ^ "Sugar Association Alternative Carbohydrate Sweeteners". http://www.sugar.org/consumers/sweet_by_nature.asp?id=277.
- ^ "International Starch Association Starch and Glucose Glossary". http://www.starch.dk/isi/starch/glosary.htm.
- ^ Trends in U.S. production and use of glucose syrup and dextrose, 1965-1990, and prospects for the future - U.S. Dept. of Agriculture, Economic Research Service report [1]
- ^ Karo website , frequently-asked questions
