Action of Ammonium Sulfate Solution on Dry Milk Powders

Milk powders dispersed in concentrated solution of ammonium sulfate maintain their structural configurations in spite of loss of lactose and calcium. In 95% saturated ammonium sulfate solutions, protein is not removed but lactose and calcium are rapidly and completely removed. In 50% saturated ammonium sulfate, some whey proteins were also removed without affecting the particles physical appearance. Some fragmentation occurred in all foam spray-dried powders probably from coalescence of interior gas bubbles in these less dense particles. Agglomerates of instantized skimmilk powder were broken down to their fundamental particles by the ammonium sulfate solutions, appearing thereafter much the same as noninstantized skimmilk particles. These phenomena indicate that, in the terminal stages of drying, proteins may interact to form a continuous phase in spray-dried milk and that lactose may be the bridging material in the formation of powder particle aggregates during instantizing.