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

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Abstract
A new method for direct measurement of the amount of .alpha.- and .beta.-lactose in whey powders by differential scanning calorimetry provides accurate results in only 2-3 h instead of 8-24 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 .alpha.-hydrate to .alpha.-anhydrous, and permits the detection of 2 melting transitions (.alpha. and .beta.). Measurement of normalized peak height gives the relative amounts of .alpha.- and .beta.-lactose in the original powder. Results are presented for whey powders with degrees of crystallinity ranging from 0-90% and for mixtures of .alpha.-hydrate and .beta.-lactose, and for lyophilized lactose. The technique measures total .alpha.-lactose content to within 5% of the value by polarimetric analysis.