High-Fructose Corn Syrup (HFCS)

High-fructose corn syrup (HFCS) is a liquid nutritive sweetener made from corn starch and composed mainly of the simple sugars glucose and fructose. Corn starch is first hydrolyzed to produce a glucose-rich corn syrup. The enzyme glucose isomerase is then used to convert some of that glucose into fructose, producing a sweeter mixture of the two sugars .^1,2

The two most common formulations are HFCS-42 and HFCS-55, containing approximately 42 percent and 55 percent fructose, respectively, on a dry-solids basis, with the remaining sugars consisting mainly of glucose. The word high in HFCS means that its fructose content has been increased relative to ordinary corn syrup, which is predominantly glucose. It does not mean that HFCS is pure fructose .^1,2

HFCS has broadly similar proportions of glucose and fructose to sucrose, or table sugar, although the exact proportions depend on the HFCS formulation and the sugars are chemically arranged differently. Sucrose is a disaccharide in which one glucose molecule and one fructose molecule are joined by a covalent bond. In HFCS, glucose and fructose are present mainly as separate monosaccharides dissolved in water. During digestion, sucrose is hydrolyzed into free glucose and fructose before absorption .¹

HFCS should also be distinguished from crystalline or pure fructose. HFCS supplies both glucose and fructose, with their proportions depending on the formulation. It is therefore best understood as a glucose-fructose syrup produced by enzymatically modifying corn-derived glucose syrup .^1,2