Corn syrup is any of a variety of forms of syrup (thick, viscous liquid, containing a large amount of dissolved sugars, with little tendency to deposit crystals) made using corn starch as a feedstock, and composed mainly of glucose. Corn syrup is a natural sweetener used in a variety of products, which may be labeled "all natural" in the United States. It is often used to soften texture, add volume, inhibit crystallization, and enhance flavor (Knehr 2005).
High fructose corn syrup (HFCS) refers to a group of corn syrups that have undergone enzymatic processing in order to increase the fructose content. This processing converts the dextrose (glucose) sugars into fructose sugars, which are sweeter.
Typically, types of HFCS include HFCS 90 (most commonly used in baked goods), which is approximately 90 percent fructose and 10 percent glucose; HFCS 55 (most commonly used in soft drinks), which is approximately 55 percent fructose and 45 percent glucose; and HFCS 42 (most commonly used in sports drinks), which is approximately 42 percent fructose and 58 percent glucose.
There is some controversy over the use of HFCS as a food additive. Increasingly, manufacturers are utilizing HFCS in a variety of foods such as breads, cereals, soft drinks, condiments, and so forth. The process by which HFCS is produced was first developed by Richard O. Marshall and Earl R. Kooi in 1957 (Marshall et al. 1957), and refined by Japanese researchers in the 1970s. HFCS was rapidly introduced in many processed foods and soft drinks in the United States over the period of about 1975–1985.
In terms of sweetness, HFCS 55 is comparable to table sugar (sucrose) (CRA 2007). This makes it useful to manufacturers as a possible substitute for sugar in soft drinks and other processed foods. HFCS 90 is sweeter than table sugar, while HFCS 42 is not as sweet as table sugar.
Since its introduction, HFCS has begun to replace sugar in various processed foods in the U.S. The main reasons for this switch are (White 1992):
HFCS is somewhat cheaper due to the relative abundance of corn, farm subsidies, and sugar import tariffs in the United States (Pollan 2003)
HFCS is easier to blend and transport because it is a liquid (Hanover and White 1993)
HFCS usage leads to products with much longer shelf life