LACTOSE (C12H22O11), also called milk sugar, is a disaccharide that consists of of b-D-galactose and a/b-D-glucose through a b1-4 glycosidic linkage. Lactose is the major sugar and makes up 2%-8% of milk. Simple, direct and high-throughput assays for lactose determination find wide applications. BioAssay Systems' assay uses specific enzyme-coupled reactions in which lactose is cleaved and the resulting galactose forms a colored product. The fluorescence intensity at 590nm when excited by 530nm is directly proportional to the lactose concentration in the sample measured by FluoroQuik fluorometer.