Impact of spray drying conditions on the reconstitution, efficiency and flow properties of spray dried apple powder-optimization, sensorial and rheological assessment

Spray drying is a preferred choice for development of highly soluble, rapidly dispersible apple powder. However, adhesion during spray drying of syrups and juices is encountered which leads to product loss. The main solution to reduce adhesion is using drying aids. Besides, control of spray drying operating parameters (inlet air temperature and feed flow rate) also closely govern the powder yield, physical, functional and microstructural properties of spray dried fruit powder. Thus, the aim of the study was to evaluate the effect of inlet air temperature (IAT), carrier agent concentration (MD:GA), feed flow rate (FFR) & feed TSS (FTSS) on moisture content, hygroscopicity, dispersibility, water solubility index (WSI), bulk density (BD), porosity (Φ), flowability, lightness (L*) and radical scavenging activity (RSA). Design expert predicted IAT of 160 °C, MD and GA concentration of 14% and 6% respectively, FFR of 350 rpm & FTSS of 15(o)Brix as optimum condition for development of easily dispersible, highly soluble and least hygroscopic powder. The powder developed after following the optimized condition (SDAP) recorded moisture content as 2.91%, hygroscopicity as 25.29%, dispersibility as 92.50%, WSI as 94.17%, bulk density as 314.1 kg/m(3), porosity as 57.19, flowability as 25.83°, L* value as 70.54 and RSA as 14.37. Among different powder reconstitution concentrations, 25% w/v concentration came out to be the best for reconstitution on the basis of sensory evaluation and rheological test. Frequency sweep test for all the reconstituted juice samples showed higher storage modulus than loss modulus for all the applied frequencies. The results of the study conferred that the developed powder could be used for commercial purpose.