A three-cascaded-enzymes biosensor to determine lactose concentration in raw milk

The increasing demand for on-line measurement of milk composition directs s cience and industry to search for practical solutions, and biosensors may b e a possibility. The specific objective of this work was to develop an elec trochemical biosensor to determine lactose concentration in fresh raw milk. The sensor is based on serial reactions of three enzymes-beta-galactosidas e, glucose oxidase, and horseradish peroxidase-immobilized on a glassy carb on electrode. The sequential enzymatic reactions increase the selectivity a nd sensitivity of the sensor. The sensor requires dilution of the raw milk and the addition of Et-aminosalicylic acid. Lactose concentrations in raw m ilk measured by the sensor were in good agreement with those measured by a reference laboratory using infrared technology. The results were obtained i n milk samples that varied in fat and protein composition. From the results , we conclude that an electrochemical biosensor for determination of lactos e concentration in fresh raw milk can be developed, and that the biosensor presented in this study maintained the qualities required for further devel opment into an online sensor in the milking parlor.