Influence of processing variables on the physicochemical properties of spray dried fat-based milk powders

An experimental programme based on the production of fat-containing milk powders was designed around a newly-commissioned pilot-scale Tall-form drier. The 2-stage drier was equipped with two external fluidised beds and had a nominal water evaporation capacity of 70 100 kg.h(-1), depending on product and process conditions. The objective was to determine the influence of process variables on the physico-chemical properties of powders containing wide ranging fat levels. Regression equations were obtained in the course of correlating powder characteristics (bulk density, free fat, moisture) to input process parameters (concentrate total solids, drier inlet temperature, fat content and stage of feed homogenisation). The interactions for cream-filled and fat-filled powders in the fat range 260 700 g.kg(-1) are outlined. A complex series of linear, quadratic and interactive relationships were established to describe the influence of processing conditions on powder quality. In addition, the processing conditions required to produce a high free fat powder as an ingredient suitable for chocolate manufacture are briefly described.