High Performance Liquid Chromatographic Determination of Lactose, Glucose, and Galactose in Lactose-Reduced Milk

A simple, rapid high performance liquid chromatographic (HPLC) method was developed to simultaneously determine lactose, glucose, and galactose in lactose-reduced milk. The sugars were separated on a Bio-Rad HPX-87C fixed ion resin column in the Ca⁺⁺ form, using water as the mobile phase and a flow rate of 0.6 ml/min. The column was heated to 80°C, and the sugars were detected using refractive index. Lactose-reduced milk was analyzed for lactose and its hydrolysis products. Milk samples were rapidly prepared for injection by precipitating protein and fat with acetonitrile. Retention times for lactose, glucose, and galactose were 9.3, 10.8, and 12.3 min, respectively. Transgalactosylation products were estimated to be at least 7.8%.