Corn syrup

Corn syrup is a food syrup which is made from the starch of maize (called corn in some countries) and contains varying amounts of maltose and higher oligosaccharides, depending on the grade. Corn syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor. Corn syrup is distinct from high-fructose corn syrup (HFCS), which is manufactured from corn syrup by converting a large proportion of its glucose into fructose using the enzyme D-xylose isomerase, thus producing a sweeter compound due to higher levels of fructose.

The more general term glucose syrup is often used synonymously with corn syrup, since glucose syrup is in the United States most commonly made from corn starch. Technically, glucose syrup is any liquid starch hydrolysate of mono-, di-, and higher-saccharides and can be made from any source of starch; wheat, tapioca and potatoes are the most common other sources.

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 Gottlieb Kirchhoff in 1812. 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 bacterium Bacillus and the enzyme is isolated from the liquid in which the bacteria were grown. The enzyme breaks down 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.