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

A new method for direct measurement of the amount of a-and ~3-1actose 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 a-hydrate to &-anhydrous, and permits the detection of two melting transitions (a-and /3).Measurement of normalized peak height gives the relative amounts of a-and/3-lactose in the original powder.Results are presented for whey powders with degrees of crystallinity ranging from 0 to 90% and for mixtures of a-hydrate and /3-lactose as well as for lyophilized lactose.The technique measures total &-lactose content to within 5% of the value by polarimetric analysis.