Influence of Spray-Drying Conditions on Size and Size Distribution of Nonfat Dry Milk Particles

Abstract

Particle size and size distribution of nonfat dry milk was determined by microscopic, sieve, and Coulter Counter methods. Data obtained by using the microscopic method indicated the smallest mean particle size, while data from the sieve method indicated the largest mean size. Results of the Coulter Counter method were changed slightly by the aperture size, but usually the curve was located between the results of the microscope and sieve. The distribution of particle size increased with an increase of total solids (30 to 50%) or a decrease in pump pressure (245 to 106 kg/cm2). Particle size was not significantly affected within the range of 121 to 177 C inlet air temperature and 63 to 85 C preheat treatment. An accurate evaluation of the particle size distribution of nonfat dry milk requires measurements by at least two methods: Coulter Counter and sieve or microscope methods. © 1969, American Dairy Science Association. All rights reserved.