Moisture Analysis and Estimation of Crystalline α-Lactose in Whey Powders

Abstract

Chemical titration, azeotropic distillation, and vacuum dehydration techniques were evaluated for determining moisture in spray-dried whey powders. Total moisture contents of cottage and Cheddar cheese whey powders are best determined with the Karl Fischer titration and toluene distillation methods, respectively. Free moisture, exclusive of water of hydration of α-lactose • H2O crystals, may be measured by drying in vacuo at 65 C at 100 torr for 6 h. Vacuum dehydration at higher temperature and prolonged toluene distillation of cottage cheese whey powder are complicated by lactic acid volatilization and by powder decomposition. High vacuum drying of sweet whey powder releases some of the water of hydration of α-lactose. Crystalline lactose contents of whey powders can be estimated within 10% of polarimetrically determined values by taking the differences between total and free moisture values. Thermogravimetry can provide a similar estimate of lactose crystallinity in dried products other than cottage cheese whey powder. © 1974, American Dairy Science Association. All rights reserved.