Effects of micro wet milling and vacuum spray drying on the physicochemical and antioxidant properties of orange (Citrus unshiu) juice with pulp powder

The aim of this study was to produce concentrated orange juice (OJ) powders by the application of two new techniques, namely micro-wet milling (MWM) and vacuum spray drying (VSD) process. MWM produced OJ with smaller particle sizes (55.0 ± 1.05 μm) than conventional methods and increased the nutritional and antioxidant properties of the concentrated juice over the commercial OJ. VSD process was conducted at low temperature (40-60 °C) using superheated steam (200 °C) as a heating medium and maltodextrin (13DE) as a carrier. The effects of VSD on physicochemical and antioxidant properties of MWM OJ powders produced with four different weight ratios of juice solids to maltodextrin solids; 60:40, 50:50, 40:60 and 30:70 were investigated. The obtained powders were analyzed for moisture content, water activity, bulk density, tapped density, particle density, porosity, and particle size and distributions and microstructure of the particles. The quality in respect to the physical properties of OJ powders was improved except color parameter with increases of maltodextrin solids. The VSD powders retained a higher amount of ascorbic acid, total phenolic content (TPC) and total flavonoid content (TFC) than spray drying. MWM orange powder with overall good quality in terms of color, yield, ascorbic acid, TFC, TPC and DPPH activity was successfully produced by VSD.