Editing Corn syrup (section)

== Commercial preparation ==
Historically, corn syrup was produced by combining corn starch with dilute [[hydrochloric acid]], and then heating the mixture under pressure. The process was invented by the German chemist [[Gottlieb Kirchhoff]] in 1811. Currently, corn syrup is obtained through a multi-step [[bioprocess]]. First, the [[enzyme]] α-[[amylase]] is added to a mixture of corn starch and water. α-amylase is secreted by various species of the [[bacteria|bacterium]] genus ''[[Bacillus]]'' and is isolated from the liquid in which the bacteria were grown. The enzyme breaks down the starch into [[oligosaccharide]]s, 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 [[Xylose isomerase|D-xylose isomerase]], an enzyme that is isolated from the growth medium of any of several bacteria.<ref>Martin Chaplin and Christopher Bucke, ''Enzyme Technology'' (Cambridge, England: Cambridge University Press, 1990), pages 146-154. Available on-line at: [https://web.archive.org/web/20121027003434/http://www.lsbu.ac.uk/water/enztech/ London South Bank University: Enzyme Technology]. See "Chapter 4: The large-scale use of enzymes in solution", sections:

* [https://web.archive.org/web/20121231050715/http://www.lsbu.ac.uk/water/enztech/starch.html The use of enzymes in starch hydrolysis]
* [https://web.archive.org/web/20130612192915/http://www.lsbu.ac.uk/water/enztech/glucose.html Production of glucose syrup]</ref>

Corn syrup is produced from number 2 yellow dent corn.<ref>"Dent corn" (''Zea mays var. indentata'') is so called because the tops of its kernels are slightly indented. See [http://www.merriam-webster.com/dictionary/dent+corn Merriam-Webster dictionary].</ref> When [[wet-milling|wet milled]], about 2.3 litres of corn are required to yield an average of 947g of starch, to produce 1&nbsp;kg of glucose syrup. A [[bushel]] (25&nbsp;kg) of corn will yield an average of 31.5 pounds (14.3&nbsp;kg) of starch, which in turn will yield about 33.3 pounds (15.1&nbsp;kg) of syrup. Thus, it takes about 2,300 litres of corn to produce a [[tonne]] of glucose syrup, or 60 bushels (1524&nbsp;kg) of corn to produce one [[short ton]].<ref name="hydrolysis">{{cite web|title=Enzymatic starch hydrolysis: background|url=http://www.bpe.wur.nl/UK/Research/Dissertations/Enzymatic+starch+hydrolysis/Enzymatic+starch+hydrolysis+background/|url-status=dead|archive-url=https://web.archive.org/web/20081004055213/http://www.bpe.wur.nl/UK/Research/Dissertations/Enzymatic+starch+hydrolysis/Enzymatic+starch+hydrolysis+background/|archive-date=October 4, 2008}}</ref><ref>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 [https://archive.today/20120708093106/http://findarticles.com/p/articles/mi_m3796/is_1991_Sept/ai_11917704]</ref>

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). Most commercially available corn syrups are approximately 1/3 glucose by weight.{{Cn|date=January 2021}}

Two common commercial corn syrup products are light and dark corn syrup.<ref name="KFAQ">{{cite web|title=Karo Syrup - FAQ|url=http://www.karosyrup.com/faq.html|website=Karo|publisher=ACH Food Companies, Inc.|access-date=15 May 2015|archive-date=11 May 2015|archive-url=https://web.archive.org/web/20150511213811/http://www.karosyrup.com/faq.html|url-status=dead}}</ref>
*''Light corn syrup'' is corn syrup seasoned with [[vanilla]] flavor and salt.  It is a nearly clear color.
*''Dark corn syrup'' is a combination of corn syrup and [[refiner's syrup]], caramel color and flavor, salt, and the preservative sodium benzoate. Its color is dark brown.