Title : The fluidized bed drying of watermelon (citrullus lanatus) rind
Abstract:
The rind of the watermelon (Citrullus lanatus) fruit is a major agricultural waste but is edible and a potential source of nutrients. The rind can be dried and converted to a powdered form which can be used in a variety of food applications. The fluidized bed drying of watermelon rind pieces was investigated as a rapid drying method to producing a high-quality dried watermelon rind powder. Rind pieces (1x1x0.5 cm) were dried in a Sherwood Scientific Tornado Fluidized Bed Dryer (Sherwood Scientific Ltd, Cambridge, UK) at 70°C (4 m/s) until there was virtually no change in weight. The dried samples were then ground to a fine powder (180 m). The initial moisture content and water activity (aw) values of fresh rind averaged 7.78 g H2O/g DM (88.43 % wb) and 0.979, respectively. Rind was dried to an average moisture content of 0.025 g H2O/g DM (2.4% wb) after 53 min, and final average water activity of 0.463. Drying occurred in the falling rate period and drying rate constants (k) averaged 0.0830 1/min, with the corresponding diffusivity values averaging 3.50 x 10-9 m2/s. The Aghbashlo et al. model was found to best fit the MR data, based on the root mean square error (RMSE) and the chi-square statistic ( 2). Dried rind samples could easily be ground into fine powders which were an attractive green colour, high in protein (16.9% wb) and fibre (24.2% wb). The results show the clear potential for fluidized bed drying as a rapid drying method of drying watermelon rind pieces to be used in the manufacture of watermelon rind powders.
