Cheap sweetener is a staple of the processed foods industry--it's used in products as diverse as stuffing and soft drinks. The cheapest of the cheap sweeteners are corn syrup and high fructose corn syrup, both of which are derivatives of a type of low-grade corn. To understand the difference between these two sweeteners, it is essential to understand corn itself and the ways in which it is processed.
Corn arriving at a processing plant is soaked in water with sulfur dioxide added to it. "The acid bath swells the kernels and frees the starch from the proteins that surround it," says Michael Pollan, author of "The Omnivore's Dilemma." The treated corn is then ground in a mill to take off the germ; spun in a centrifuge to separate the germ from the starch-protein complex; and then repeatedly goes through the same process to get pure starch.
Starch is a complex carbohydrate. This simply means that it is a long chain of sugars; the human body must expend calories to break down these chains into simple sugars that the body can then use as a further source of energy. Corn starch becomes corn syrup when the refiner introduces an acid to break the bonds of the complex carbohydrate. Thus, corn syrup is what MedlinePlus describes as "a liquid combination of maltose, glucose and dextrose sugars."
An enzyme, glucose isomerase, causes a reaction with corn syrup. Marci Pezzuto and Stephen Popielarski, chemical engineers, state that the reaction creates fructose, which is "twice as sweet as sucrose." In essence, high fructose corn syrup is created by turning much of the glucose in plain corn syrup into fructose, thus increasing the sweetness of the liquid.
Both corn syrup and its counterpart are used in liquid form. They retain moisture better than crystallized sugar because water is a large part of their chemical makeups. Sweet Surprise, a website run by the Corn Refiner's Association, specifically cites the use of high fructose corn syrup as a preservative that "prolongs product freshness in breads, provides product stability in condiments" and inhibits the growth of microbes.
A 2010 study published in the scholarly journal Pharmacology, Biochemistry and Behavior found that compared with similar consumption of table sugar, consumption of high fructose corn syrup caused "an increase in adipose fat, notably in the abdominal region, and elevated circulating triglyceride levels" in rats. Other studies comparing metabolism of a variety of sugars with that of high fructose corn syrup have had mixed results.