... washing, slicing, extracting, filtrating, purifying, concentrating, sterilizing(pur purple sweet potato color/natural food colouring ple sweet potato color ... When PH is between2-6, the color is red or purple red .The solution color becomes blue, and is unstable ... than1,0001,000Pathogenic Bacteria NegativeNegative Applications and Usage Instruction: Purple sweet potato color can be widely used in wine, ...