Study on enzyme-ultrasonic combined extraction method of purple sweet potato pigment

The enzyme-ultrasonic combined extraction method of purple sweet potato pigment was studied by single factor experiment and L9 (34) orthogonal experiment. The results showed that the optimum extraction conditions were obtained as follows:cellulase dose 20IU/g, enzymatic hydrolysis time 45min, enzymatic hydrolysis temperature 50℃, enzymatic hydrolysis pH5.6, solid-liquid ratio 1 ∶10, ultrasonic time 20min and ultrasonic temperature 60℃. Under the optimum conditions, the extraction rate reached up to 98.7% after three times extractions. Furthermore, the three extraction methods (enzymatic extraction, ultrasonic extraction and enzymeultrasonic combined extraction) were compared. The pigment extraction rate of enzyme-ultrasonic combined extraction method increased by 39.3% and 20.3% respectively compared to that of enzyme extraction and ultrasonic extraction. The results of this study indicated that pigment extraction rate of enzyme-ultrasonic combined extraction method was the highest. This study would provide a new extraction method for purple sweet potato pigment.