Effect of drying and grinding methods on physical and hydration properties of sweet orange peel powder

During the sweet orange juice extraction process a large quantity of peel is produced which is a waste. At present, peel is used for animal feeds and as a source of dietary fibres due to their high fibre content. It could an interesting source of dietary fibre for food also. Efforts were made to investigate the effect of four drying methods (open yard sun drying, solar tunnel drying, hot air drying and dehumidified air drying) and three grinding methods (hammer mill grinding at ambient temperature, with water cooling and with liquid nitrogen cooling) on functional properties of sweet orange peel powder are reported here. Among all combinations of treatments, dehumidified air drying and hammer mill with LN₂ grinded powder showed the highest specific volume, lowest bulk density and apparent density due to good hydration properties with highest swelling capacity, water retention capacity, water holding capacity and oil holding capacity. It concluded that powder can be rich source of dietary fibres.