Effect of operating parameters on the surface and physico-chemical properties of spray-dried camel milk powders

The effect of process variables of spray drying on the surface and physico-chemical properties of camel milk powder was evaluated. A 23 full factorial experimental design was used to determine the effects of inlet temperature (200 °C, 170 °C and 140 °C), drying air flow rate (9, 7.5 and 6 m3/min) and total solids of skimmed camel milk (40, 24 and 8.2%) on cyclone recovery and outlet temperature. These variables were found to affect the level of cyclone recovery and outlet temperatures. Cow milk powder was prepared under similar conditions and used for comparison of powder bulk densities. The bulk densities of the powders ranged from 0.17 to 0.63 g/cc. The bulk densities of camel milk powders were higher (p < 0.05) than those of cow milk processed under similar conditions. The glass transition temperature of the powders ranged from 37.8 to 40.45 °C. The SDS-PAGE electrophoretic properties of the powders demonstrated that operating at lower spray drying temperature ranges (140 °C) is important for minimizing loss of the solubility of camel milk proteins. The Scanning Electron Microscopy images of the powders illustrated that fats on the surfaces of whole milk powders contribute to cause aggregation of neighbouring powder particles together.