Calorimetry and Thermogravimetry of Bound Water in Dried Milk and Whey Powders

Abstract

Thermal data show that water is sorbed by milk and whey powders through primarily weak binding forces at low to intermediate relative humidities. Heat required to release and vaporize such bound water, as determined by differential scanning calorimetry is 10.1 ± 0.4 kcal per mole of water desorbed from whole or skimmilk powders. When milk or whey powders sorb sufficient water, at ≥ 50% relative humidity, to induce lactose crystallization or changes in protein conformation, the differential scanning calorimetry pattern becomes more complex, desorption is completed at a higher temperature and the enthalpy of desorption increases by 1.44 to 2.44 kcal per mole. © 1971, American Dairy Science Association. All rights reserved.