Adhesion is the most important factor in product loss in the spray drying of syrups and juices. The main solution to reduce adhesion is using drying aids. The aim of this study was to evaluate effect of maltodextrin (MD) and gum Arabic as drying aids, and pectin and whey protein concentrate (WPC) as complementary drying aid on the powder yield, physical, functional and microstructural properties of spray dried apple juice concentrate. The studied variables and composition of the carriers were used. The inlet air temperature, atomizer rotational speed, feed flow rate, feed temperature and atomizer pressure were kept constant at 160 °C, 18,000 rpm, 15 ml/min, 25 ± 1 °C and 4.2 ± 0.1 bar, respectively. The results of powder production yield indicated that WPC was more effective than pectin as complementary drying aid. The bulk and tapped density of powders significantly decreased with an increase in WPC ratio. Moisture content, solubility, wettability, hygroscopicity and color parameters of the powders were also influenced by the carriers` type and their combinations. The microstructure of spray dried powders showed various particle sizes with spherical and irregular shapes (with shrinkages and dents on the surface). Taking into account all the parameters, 10% WPC in combination with MD was used which showed the best results in the economic production of powder with the highest yield (60.85%) and appropriate physical, flowability and functionality properties.
Keywords: Apple juice concentrate; Carrier; Microstructure; Spray drying; Whey protein concentrate.