Inspection and Cleaning

• Corn kernels arrive at a refining plant and undergo two inspections by the refinery staff. Each day's delivery is roughly equivalent to the harvest of 33,000 acres of cornfields. Removal of debris such as bits of cob or leaf and dust takes place before the refining process begins.
  
  

Steeping

• The cleaned corn kernels soak for 30 to 40 hours in stainless steel tanks. The soaking medium consists of a 0.1 percent solution of sulfur dioxide in water, kept at 50 degrees Celsius. During this time, the kernels swell to more than twice their original size. The mildly acid environment retards bacterial growth as well as loosens the gluten bonds of the corn. The swollen kernels, coarsely ground to release the germ from the rest of the kernel, move on the germ separators.
  
  

Germ Separation

• Cyclone separators separate the germ from the slurry. Processing the germ yields corn oil and animal feed components.
  
  

Fine Grinding and Screening

• The slurry continues on its way to another, more intense grinding to separate fiber, starch and gluten. A series of screens hold the fiber while the starch and gluten move on in a form called mill starch.
  
  

Starch Separation

• Centrifugal force separates gluten from starch. After repeated dilutions and washings, the purified starch is ready for conversion into corn syrup.
  
  

Syrup Conversion

• Refiners add acid and/or enzymes to a suspension of starch and water. The resulting low-dextrose mixture gets treatment with another enzyme so the process continues. Depending on when refiners interrupt the process, the product will be low dextrose syrups, sweeter high dextrose syrup, or some sweetness level in between.
  
  The syrup passes through equipment to refine it and evaporate extra water. This product may be "sold directly, crystallized into pure dextrose, or processed further to create high fructose corn syrup," says the CRA. "Corn syrup is a mildly sweet, concentrated solution of dextrose and other sugars derived from corn starch. It is naturally sweet. Corn syrup contains between 15 to 20 percent dextrose (glucose) and a mixture of various other types of sugar," according to the makers of Karo syrup. Some commercially available corn syrups are flavored.
  
  

Caution

• Corn syrup is sweet, but it is not freely interchangeable with sugar in recipes. Differences in sweetness levels, as well as the additional liquid content can wreck a recipe.