Fructose powder is pure, powdered fructose. It looks quite a bit like table sugar, though the granules are typically slightly smaller, and tastes significantly sweeter than table sugar. You can purchase fructose powder at many grocery stores and most health food stores, and use it as a substitute for table sugar in foods and baked goods.
Fructose is a chemical component of table sugar. Sucrose, the chemical name for table sugar, is a large molecule made up of a fructose molecule chemically bonded to a glucose molecule. Both fructose and glucose are monosaccharides, which means single sugar unit. Bonded together in the form of sucrose, they form a disaccharide, which means double sugar unit. Since fructose tastes quite a bit sweeter than glucose, when they're combined in the form of sucrose, the combination has a sweetness between that of glucose and fructose.
Pure fructose isn't common in nature -- most of the fructose you consume from natural sources is chemically combined with glucose in the form of sucrose. Fruit does contain some pure fructose, however. Through the process of photosynthesis, plants make both glucose and fructose. Some of these monosaccharides, the plant leaves unmodified in pure form -- this is the source of pure fructose in fruit. It's possible, but not particularly practical, to isolate pure fructose from fruit.
Most of the fructose used to make fructose powder comes from corn, which doesn't contain fructose in its natural form. To obtain fructose from corn requires a series of chemical reactions. Corn is a rich source of amylose, or starch. Amylose is made up of long chains of glucose molecules, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry." Manufacturers chemically react amylose with an enzyme called amylase to break the starch down into glucose. They then react the glucose with another enzyme called invertase to convert the glucose into fructose, which they purify and crystallize.
Uses of Fructose Powder
You can use fructose powder in many of the same ways you use table sugar. While both sucrose and fructose contain identical numbers of calories -- 4 per gram -- since fructose is much sweeter, you don't need to use as much of it to sweeten food. This means that fructose-sweetened foods are typically slightly lower in calories than sucrose-sweetened foods. There is some research that suggests consuming fructose instead of sucrose or glucose isn't heart healthy. A 2000 study published in the "American Journal of Clinical Nutrition" notes that fructose may increase your blood lipid levels.