Rapid determination of lactulose in milk using Seliwanoff's reaction

A rapid method based on Seliwanoffs reaction to distinguish between UHT and sterilised milk was proposed. Lactulose was determined directly in milk with no treatment. Analysis of raw milk and its carbohydrates showed that the only interference was the relatively high concentration of lactose, which imposes the lower limit of detection. Small variations of lactulose (9 mg dL(-1)) during heat treatment could be observed when the absorbance was measured against pre-treated milk (blank). This method showed a linear range between 17 - 170 mg dL(-1) and a detection limit lower than that of the official HPLC method, This novel procedure was compared with a commercially available enzymatic method and the results obtained correlated well.