3.4.2. Spray-Drying

Three formulations were prepared by spray-drying: (i) a control sample, consisting of 100% fruit juice; (ii) a formulation containing fruit juice added with 40% maltodextrin; and (iii) a formulation composed of fruit juice added with 20% of a 1:1 (w/w) maltodextrin arabic gum mixture. The referred percentages were selected after testing different contents of maltodextrin and maltodextrin + arabic gum (1:1, w/w), and are expressed as the ratio of the drying adjuvants weight relative to the total solids weight in the prepared juice (100 mg/mL). These formulations were spray-dried according to the procedure of Moser et al. [38], analysing the efficiency of the drying process and the suitability of the used drying coadjutants, maltodextrin and arabic gum. The solutions were prepared immediately before atomization by mixing the fruit juice with the selected materials under stirring at room temperature for 10 min. A Mini Spray Dryer B-290 (Büchi, Flawil, Switzerland) programmed in the normal operation mode (nozzle diameter: 0.7 mm; atomized volume: 200 mL, solids content < 33%) was used. The optimized operation conditions were an inlet temperature of 140 °C, an outlet temperature of 72 °C, an aspiration of 90%, with the pump working at 20% (6 mL/min). To calculate the yield of the process, expressed in percentage, the ratio between the obtained powder weight and the initial solution’s total solids weight (dry-basis), was considered.