Determination of lactose in milk by high resolution ultrasonic spectroscopy

Abstract

The application of high-resolution ultrasonic spectroscopy for determination of the amount of lactose in milk and milk-based drinks is described. The methodology is based on high precision real time ultrasonic monitoring of hydrolysis of lactose in milk by the enzyme β-galactosidase, allowing for quantitation of lactose present at reaction completion. The method can also be used to control in real-time the hydrolysis of lactose for the precise preparation of milks with preferred lactose concentrations. The elimination of sample preparation steps and the minimal need for user interaction represent significant simplification and time savings over existing methods. Comparison of the ultrasonic data with results from HPLC-RI showed excellent agreement in the determination of lactose in normal, skimmed and chocolate milks.