Glucose syrup, also known as confectioner’s glucose, is a syrup made from the hydrolysis of starch. Glucose syrup was first made in 1811 in Mizuame by Gottlieb Kirchhoff using heat and sulfuric acid.
Depending on the method used to hydrolyse the starch and on the extent to which the hydrolysis reaction has been allowed to proceed, different grades of glucose syrup are produced, which have different characteristics and uses. The original glucose syrups were manufactured by acid hydrolysis of corn starch at high temperature and pressure. The typical product had a DE of 42, but quality was variable due to the difficulty of controlling the reaction. Before conversion of starch to glucose can begin, the starch must be separated from the plant material. The starch needs to be swelled to allow the enzymes or acid to act upon it. When grain is used, sulfur dioxide is added to prevent spoilage.
By heating the ground, cleaned feedstock, starch gelatinization takes place: the intermolecular bonds of the starch molecules are broken down, allowing the hydrogen bonding sites to engage more water. Glucose syrup can be produced by acid hydrolysis, enzyme hydrolysis, or a combination of the two. Currently, however, a variety of options are available. Formerly, glucose syrup was only produced by combining corn starch with dilute hydrochloric acid, and then heating the mixture under pressure. Currently, glucose syrup is mainly produced by first adding the enzyme α-amylase to a mixture of corn starch and water. After hydrolysis, the dilute syrup can be passed through columns to remove impurities, improving its colour and stability. The dilute glucose syrup is finally evaporated under vacuum to raise the solids concentration.