What is the difference between reducing and non reducing sugar?

Answer 1

The Fehling's and the Benedict's Test are the just two of the many tests conducted in identifying reducing and non-reducing sugars. Reducing sugars like the monosaccharides can reduce cupric hydroxide from the reagents used.

This is because the reducing sugars have a free oH group at their anomeric carbon that can cause the reduction of mild oxidizing agents like fehling and Benedict solution.In non reducing sugars this oH is involved in glycosidic bond formation.

Answer 2

Saccharides bearing anomeric carbon atoms that have not formed glycosides are named reducing sugars. The most common example is glucose. In these sugars, there is a facility with which the aldehyde group reduces mild oxidizing agents. The most common test for the presence of reducing sugars is the reduction of Ag+ in an ammonia solution (the so-called Tollens' reagent) to yield a metallic silver mirror lining of the reaction tube. Moreover, reducing sugars can be oxidized in their anomeric carbon by relatively mild oxidizing agents such as ferric (Fe3+) or cupric (Cu2+) ion. Oxidation of anomeric carbon is the basis for Fehling's reaction.

Sugars that do not contain an aldehyde or potential aldehyde group, and therefore cannot reduce inorganic ions in solutions as described above, are called nonreducing sugars. The most common is sucrose or table sugar.