Starch, suspended in water, is liquefied in the presence of acid and/or enzymes which convert the starch to a low-glucose solution. Treatment with another enzyme continues the conversion process.
Throughout the process, refiners can halt acid or enzyme actions at key points to produce the right mixture of sugars like glucose and maltose for syrups to meet different needs. In some syrups, the conversion of starch to sugars is halted at an early stage to produce low-to-medium sweetness syrups. In others, the conversion is allowed to proceed until the syrup is nearly all glucose. The syrup is refined in filters, centrifuges, and ion-exchange columns, and excess water is evaporated. Syrups are sold directly, crystallized into pure glucose, or processed further to create high fructose corn syrup.