Comparison of maltodextrin and skim milk wall deposition rates in a pilot-scale spray dryer

The relative amounts of wall deposition between skim milk and maltodextrin have been compared in a pilot-scale spray dryer of 1.5 m height, equipped with a two-fluid atomizer. The atomizer air pressure was 200 kPa, the inlet air temperature was 230 degrees C, the liquid feed flowrate was 1.6 L h(-1), and there was no swirl at the air inlet. Both maltodextrin and skim milk, both with a solids content of 9% by mass, were each sprayed in three repeat experiments. The same rates of cohesion and adhesion were observed for skim milk, while the maltodextrin (DE 18) showed lower overall deposition rates, and particularly a lower rate of adhesion than for the subsequent cohesion of particles to each other after the initial spraying period. The differences in the cohesiveness and adhesiveness of maltodextrin have also been noted by previous workers, and the lower deposition rates with maltodextrin than with skim milk are consistent with the higher glass transition temperature for dry maltodextrin. (C) 2007 Published by Elsevier B.V.