Sweet potato (100g) was cut into small pieces and homogenized in 200ml of pre-chilled (4°C) 0.1M phosphate buffer using blender for 1 minute at maximum speed. The slurry was centrifuged at 9000 rpm at 4°C for 15 minutes. The supernatant obtained was filtered under vacuum from a buncher funnel containing Whatman® No. 1 filter paper and the filtrate was collected in a conical flask. Then, 100ml of the filtrate was pipette drop by drop into 200ml of cold acetone (-20°C) for the formation of the precipitates. The precipitates, crude PPO as separated by centrifugation at 9000 rpm at 4°C for 15 minutes. The resultant light brown coloured acetone precipitates was dried overnight at room temperature. The acetone powder that obtained was stored at -20°C. The enzyme extraction from acetone powder was conducted by mixing 0.1g acetone powder, 15 ml of pre-chilled 0.1M phosphate buffer, pH 6.8 and stirring for 1 hour at 4°C with a magnetic stirrer. The temperature was maintained by covering the beaker with aluminum foil and was enclosed with ice surrounding the beaker. The suspension was centrifuged at 7500 rpm for 30 minutes at 4°C. The supernatant was used as crude PPO.