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Is Sucrose a Reducing Sugar?

The common name for sucrose is table sugar. Just as the name implies, sucrose is used throughout the world as a sweetener for cooking, baking and sweetening edibles. Sucrose is commonly made by refining plant matter, such as sugarcane or sugar beets. In its most commonly used form, it is a white, orderless powder that is sweet to the taste. Although sucrose is a disaccharide, it is not a reducing sugar.

Definition
- If a sugar contains aldehyde groups that are oxidised to carboxylic acids, then that sugar is classified as a reducing sugar. It is called a reducing sugar because it reduces the number of chemicals present in its structure through oxidation.
Examples
- Reducing sugars include glucose, fructose, glyceraldehyde, lactose, arabinose and maltose.
Disaccharide
- Sucrose is a complex carbohydrate known as a disaccharide, meaning made up of two simple carbohydrates or monosaccharides. The monosaccharides that form sucrose are glucose and fructose.
Significance
- Although both glucose and fructose are reducing sugars, sucrose is not because it does not contain anomeric hydroxyl groups, and does not reduce the chemicals present in its structure through oxidation.
Identification
- It is possible to test a substance such as sucrose for the qualities that make it a reducing sugar using Fehling's solution, a mixture of copper sulfate, distilled water, Rochelle salt and sodium hydroxide. In the presence of reducing sugars, the copper sulfate in the solution will oxidize and turn red.

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