Food labels contain a stunning variety of ways to refer to what is, in essence, sugar. Different sweetening agents added to food all bind to the sweetness receptor in the mouth, leading to their flavor. Chemical differences between sweeteners, however, mean that different sugars are often processed by the body in different ways. High fructose corn syrup and brown rice syrup are two common sugaring agents added to foods.
Both brown rice and corn, like all starchy grains and foods, contain large quantities of the chemical amylose. Amylose consists of long chains of glucose molecules, where glucose is a monosaccharide, or single sugar unit. If you ate plain glucose that wasn't chemically bonded to anything else, it would bind to the sweetness receptor and taste like sugar. Bound together in long chains, however, glucose molecules assembled into amylose don't taste sweet; for this reason, if you eat brown rice or corn, you don't taste sugar, even though it's there.
Any grain, since it's a source of amylose, is also a source of glucose. It's possible to take a grain, such as corn or brown rice, and extract the amylose. By processing the amylose with a variety of enzymes, which are digestive chemicals that break the amylose into smaller pieces, you obtain a syrup that consists of individual glucose units; units of two glucose molecules connected to one another, called maltose; and units of three glucose molecules connected to one another, called maltotriose. Different levels of digestion produce different ratios of glucose, maltose and maltotriose.
High Fructose Corn Syrup
To make high fructose corn syrup, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry," corn amylose is enzymatically digested to completion, that is, until all glucose units are independent of one another. The resulting syrup, corn syrup, tastes slightly less sweet than table sugar. Processing plants then use another enzyme, called invertase, to turn half of the glucose into a related sugar called fructose, which is much sweeter. The resulting mixture of 50:50 glucose and fructose tastes as sweet as table sugar and is called high fructose corn syrup.
Brown Rice Syrup
To make brown rice syrup, manufacturers digest amylose into a blend of maltotriose, maltose and glucose. The maltose is about 40 percent as sweet as table sugar and the maltotriose is about 30 percent as sweet as table sugar, explains the Amano Enzyme Company. Brown rice syrup doesn't taste as sweet as table sugar, but because all sugars — regardless of how sweet they taste — have identical caloric content per unit mass, brown rice syrup contains the same number of calories per gram as high fructose corn syrup and table sugar.
All sources of sugar — table sugar, high fructose corn syrup, brown rice syrup and others — provide energy, and your body can convert them to fat if you eat them in large quantities. There's some evidence that eating large quantities of high fructose corn syrup affects cellular signaling and increases risk of type 2 diabetes and obesity, notes a 2004 study by Dr. George Bray and colleagues in the "American Journal of Clinical Nutrition."