A simple and fast method for the determination of Lactose and Lactulose has been evaluated. The method is based on the correlation of pH differences, measured with a glass electrode, generated by H⁺ or OH^- produced in the medium by enzymatic reaction. The result, obtained determining Lactose and Lactulose were compared with HPLC. The procedure based on the differential pH-measurements has been found to give results comparable to that of official method. The precision obtained using the two procedures was not significantly different.

The proposed method is resulted simply and fast (less then 4 minutes) , particularly for the lactulose evaluation considering no pre-treatment of the sample is required for measurements which are also automatically recorded. We suggest using the proposed method, based on differential pH-technique, for routine determination of Lactose and Lactulose in row and UHT process treatment.