Functional and reconstitution properties of spray-dried sweetened yogurt powder as influenced by processing conditions

The influence of spray-drying conditions on functional and reconstitution properties of sweetened yogurt powder was studied. Twenty experiments with different spray-drying conditions (140–180°C inlet air temperature, 0.3–0.6 L/h feed rate and 500–1000 kPa atomization pressure) were performed according to central composite experimental design. Analysis of experimental data of solubility and dispersibility of yogurt powder revealed negative correlation with inlet air temperature and atomization pressure. Solubility of powder was significantly (p < 0.05) affected by feed rate. Wetting time of powder increased significantly (p < 0.001) with the increase of spray-drying temperature. The bulk, tapped, and particle densities were in the range of 344.8–475.7, 551.7–782.5, and 1187.5–1666.7 kg/m3, respectively. A significant quadratic effect (p < 0.001) of inlet air temperature and atomization pressure was observed on bulk density. Particle density increased with the increase in inlet air temperature and atomization pressure (p < 0.001). The results of the present investigation has the credible evidence to support that the processing conditions viz. inlet air temperature and atomization pressure decreased the water activity and flow property of the sweetened yogurt powder, whereas feed rate showed positive effect.