Sucrose is a non reducing sugar because

It has a glycosidic linkage between  C-1 of α-D-glucopyranose and C-2 of β-D-fructofuranose;The -OH groups of functional group carbon atoms of both glucose(C-1) and fructose(C-2) are invoved in glycosidic linkage;No free anomeric -OH group;Both glucose and fructose are in acetal form;It is a non reducing sugar;