Specific Surface Areas of Milk Powders Produced by Different Drying Methods

Abstract

Low-temperature (−195 C) adsorption of N2 was used to study the physical surface features of whole and skimmilk powders produced by different drying techniques. Specific surface areas were calculated using the Brunauer-Emmett-Teller (BET) multilayer adsorption theory. All the milk powders exhibited rather low surface areas (∼ .1-.6 m2/g) and abnormally low values for the energy of adsorption of N2. Comparison of these surface areas with those obtained by permeametry yielded information on the relative porosities of the various powders. Conventional spray-dried powders were less porous than the instantized powders and the spray-dried foams. In addition, the surface areas of several milk constituents, including lactose, α-lactalbumin, β-lactoglobulin, and Na-α-caseinate, were measured. © 1964, American Dairy Science Association. All rights reserved.