Drying of Single Drops of Foamed and Nonfoamed Sodium Caseinate Solutions

The effects of dissolved and dispersed gases on the drying of single, macrodrops of sodium caseinate containing 15% w/w solids were investigated. Moisture and temperatures of 1-and 2-rag drops were measured during drying at 100 and 200 C in desiccated air. Foaming markedly increased the rate of drying for drops of equal mass and volume when compared to nonfoamed drops. Drops foamed with insoluble gases dried as fast as those foamed with soluble gases. Dissolved gases at equilibrium with pressures of less than 1 atm in unfoamed drops improved the rate of drying at 200 C but had no effect at 100 C. The improved quality of foam spray-dried products is explained by the kinetics of thermal degradation.