Rapid Determination of α-Lactose in Whey Powders by Differential Scanning Calorimetry

Abstract

A new method for direct measurement of the amount of α- and β-lactose in whey powders by differential scanning calorimetry provides accurate results in only 2 to 3 h instead of 8 to 24 h required by the standard polarimetric method. Treatment of a whey powder with anhydrous methanol (2 h at room temperature) prior to a calorimetric analysis removes moisture, converts α-hydrate to α-anhydrous, and permits the detection of two melting transitions (α and β). Measurement of normalized peak height gives the relative amounts of α- and β-lactose in the original powder. Results are presented for whey powders with degrees of crystallinity ranging from 0 to 90% and for mixtures of α-hydrate and β-lactose as well as for lyophilized lactose. The technique measures total α-lactose content to within 5% of the value by polarimetric analysis. © 1978, American Dairy Science Association. All rights reserved.