Glucose and fructose are two monosaccharides that form Sucrose. They both are held together by a glycosidic linkage between C1 of glucose and C2 of fructose as shown below. (––‌CHO‌––‌
O
∥
C
‌––) Since, the reducing groups of both glucose and fructose are involved in glycosidic bond formation they are not available for the reduction reaction. Hence, sucrose is a non- reducing sugar.