Study on the microwave-assisted extraction and purification technology of purple pigment from Ipomoes batatas L. pomace

Using fresh Ipomoes batatas L. pomace as material, the technology of microwave-assisted extraction of purple pigment (PP) was studied. The effects of main factors such as extraction solvents, ratio of solid to liquid, temperature and time of microwave extraction, microwave power were investigated. On the basis of single factor test, the optimized extraction conditions of purple pigments from I. batatas L. pomace obtained with an orthogonal design L9 (34) were solid/liquid ratio, extraction temperature, time and microwave power as1∶5 (g/mL) , 70℃, 5min and 600 W, respectively. The PP were then purified by resin and the resin AB-8 showed the best adsorption and desorption effect among the tested 14 kinds of resins. Its optimized purification conditions obtained by static adsorption, desorption and dynamic adsorption experiments were the absorbance, adsorption time, temperature, pH of PP, feeding flow rate, eluent as 0.5⁰.7, 1h, about 30℃, 2³, 1mL/min, and95% ethanol, respectively. Under this condition, the color scale E (524nm) of purificatory PP was 41.3.