Effect of Temperature on Porosity of Dried Whole Milk Powder Granules

Densities of spray-dried whole milk foam were measured at 25, --80, and --195 C by pycnometric techniques, using lIe or N: as the displaced medium. Evidence was obtained for marked thermal contraction of the powder particles at the lower temperatures, with associated closing of the pores on the powder surface. These effects were manifested in decreased rates of diffusion o the gases to the interior of the powder particles as the temperature was lowered.