Glucose syrup consists of a mixture of glucose and water. It has a thick, syrupy consistency, and appears both in cooking and as an aid in certain medical situations. As the most common source of glucose for glucose syrup is corn, it's quite common to hear glucose syrup referred to as corn syrup --- these are essentially synonymous.
Glucose
Glucose is a monosaccharide, which means that it's a molecule consisting of a single sugar unit. Composed only of carbon, hydrogen and oxygen, glucose is a relatively small molecule that is quite ubiquitous in nature. It occurs on its own, as well as in chemical combination with other monosaccharides, including additional units of glucose and units of other related sugars. Starch and table sugar are both common dietary sources of glucose.
Glucose Syrup
To make glucose syrup, manufacturers begin with a source of glucose in the form of starch, which goes by the chemical name amylose. Drs. Reginald Garrett and Charles Grisham explain in their book "Biochemistry" that amylose consists of long chains of glucose molecules chemically bonded together. Amylose, or starch, doesn't taste sweet when you eat it because the long chains can't bind to sweetness receptors on the tongue.
Processing
Using chemicals called enzymes, manufacturers "digest" the amylose, breaking the bonds between glucose units and producing pure glucose. Enzymes are chemicals that help reactions take place more quickly than they otherwise would --- your own body relies upon a wide variety of enzymes to help you digest your food, explains Dr. Lauralee Sherwood in her book "Human Physiology." Once amylose is broken down into glucose, it tastes sweet, because glucose binds strongly to sweetness receptors.
Uses
You can use glucose syrup in several different ways. While it's not quite as sweet as table sugar, it nevertheless has applications in cooking, and many recipes call for corn syrup. Diabetics sometimes also use glucose syrup to help treat hypoglycemia, or low blood sugar. Hypoglycemia is a condition that occurs in insulin-dependent, or Type 1, diabetics. It occurs if a diabetic doesn't eat regularly or takes too much insulin, and it can be life-threatening if not treated with a source of glucose.
Expert Insight
Glucose syrup isn't the same thing as high-fructose corn syrup, though it's possible to further process regular corn syrup to make the high-fructose variety. To make high-fructose corn syrup from regular corn --- or glucose --- syrup, manufacturers add an additional enzyme called invertase, note Garrett and Grisham. This enzyme converts some of the glucose into fructose, sweetening the mixture and making it equivalent in sweetness to table sugar, though the chemical difference between table sugar and high-fructose corn syrup is significant.
References
- "Biochemistry"; Reginald Garrett, Ph.D., and Charles Grisham, Ph.D.; 2007
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
