Physical State of Lactose as Influencing the Determination of Moisture in Dry Milk Products by the Toluene Distillation Method

Abstract

Dried skimmilk and dried whey containing lactose in the crystalline α hydrate form require appreciably longer heating times for the removal of moisture than do similar products containing the lactose in the glass or crystalline β anhydride form. Determination by oven drying, of the moisture content of different types of dried whey, presents considerable difficulty due to the differences in acidity, amount of fermentation products, per cent and physical state of the lactose, and method of heating and degree of vacuum in the oven. The toluene distillation method possesses distinct advantages for the determination of the moisture in dried milk, dried whey, and dried casein. The moisture loss time relationship can be determined without interrupting the process or interfering with the determination. The moisture loss time relationship indicates the completeness of removal of moisture, and often indicates whether more than one mechanism is involved in the loss of moisture. © 1938, American Dairy Science Association. All rights reserved.