Total free sugars, reducing sugars and glucose

Carbohydrates in the tissues of crustaceans exist as free sugars and as bound with proteins (Saravanan, 1979). The free sugars in haemolymph consist of mono, di and oligosaccharides. All monosaccharides, maltose and its oligosaccharides constitute the total reducing sugars. Trehalose constitutes the non-reducing sugar fraction of the total free sugars. The total free sugars are estimated by Anthrone method and reducing sugar by Nelson-Somogyi method. The difference in the values obtained by these two methods indicates total non-reducing sugar value which is primarily trehalose in crustacean blood. The glucose can be determined by Glucose-oxidase method. The difference between values of glucose and reducing sugars would indicate the concentration of non-glucose reducing sugars