English abstract
Oman is one of the major date producers in the world. However, it exports only around 3% of the produced dates. Also, almost half of the produced dates have not been utilized and considered as surplus. Thus, utilization of surplus dates and value addition to low price dates are very important for sustainable cultivation of dates in Oman. The objective of this study was to produce date powder from Naghal date variety at three ripening stages (khalal, rutab and tamr) using foam-mat freeze drying method. The date powder was produced with two carrier agents (maltodextrin, gum arabic) at two concentration levels (40%, 50%). The produced date powder was characterized by their physicochemical properties. The moisture content and water activity of powder were ranged from 7.06 to 12.51% and 0.14 to 0.45, respectively. The bulk density and tapped density were in the range of 0.35 to 0.70 g/cm and 0.75 to 0.90 g/cm2. Similarly, particle density and porosity of date powder were ranged from 1.45 to 2.01 g/cm2 and 39.88 to 53.39%, respectively. The date powder produced with 50% gum arabic in khalal stage had good flowability. However, all the produced powder had intermediate cohesiveness. The hygroscopicity and degree of caking of date powder were in the range of 0.088 to 0.188 g of water/g of powder and 20.35 to 99.12%, respectively. The carrier agent added date powder had around 80% of solubility index and more than 120% of water absorption index. The total phenolic content of date powder was ranged from 83.58 to 286.63 milligrams of gallic acid equivalents (GAE) per 100 g of powder. In general, gum arabic added date powder had good physical and chemical properties for all three ripening stages. Among the produced date powder, 50% gum arabic added in khalal stage powder was the best one which had good physicochemical and functional properties. The cost of production of date powder was approximately from 0.972 to 1.776 OMR/kg. The good physicochemical characteristics of date powder suggested the potential of using it in many industrial applications. Also, foam-mat freeze drying technique has good feasibility to produce free flow date powder from surplus dates.
