Effects of hot air and freeze drying methods on physicochemical properties of citrus 'hallabong' powders

Citrus 'Hallabong' powders were prepared using hot air and freeze drying methods, and their physicochemical and flow properties were measured. The yields of the powders from whole fruit and pressed cake by hot air drying method were 17.5 and 22.0%, while those by freeze drying method were 20.0 and 22.5%, respectively. Vitamin C was high in freeze-dried whole fruit powders (220.8-364.7 mg/100 g) compared with those in hot air-dried ones (80.1-114.6 mg/100 g). Browning index of freeze-dried powders was significantly lower than those of hot air-dried ones. Bulk densities, compaction densities, and Hausner ratios of the powders were significantly higher in freeze drying method compared with hot air drying method. Water solubilities and hygroscopicities of freeze-dried powders were higher than those of hot air-dried ones. In conclusion, 'Hallabong' powders can be made using freeze drying method with high quality in terms of vitamin C content, color, and water solubility.