Microwave-assisted Extraction of Pigment from Pitaya Peel and Its Functional Activity

The microwave-assisted extraction of pigments from pitaya peel was optimized,and the functional characteristics of pigments were studied. The optimum conditions of microwave-assisted extraction were optimized by using orthogonal test,and then the extracts were freeze-dried in vacuum to analyze the antimicrobial and antioxidant activities. The results showed that the extraction effect of pigment from pitaya peel was the best when the ethanol concentration was 20%,the microwave power was 440 W,the microwave time was 60 s,the liquid ratio was 1∶50 (g/mL),and the maximum yield of pigment was 1.074%. The results of antioxidant test showed that the 2~10 mg/mL pigment extracts had scavenging effect on hydroxyl radical(·OH),superoxide anion radical(O₂^-·)and DPPH·.Among them,the scavenging effect on O₂^-· was the best,which was equivalent to the removal effect of V_C. The antibacterial test of the pigment extracts showed that the minimum inhibitory concentration of the extract on Escherichia coli was 1.25 mg/mL,and the minimum bactericidal concentration was 2.5 mg/mL. The inhibitory effect was the best on Escherichia coli,followed by Staphylococcus aureus,Vibrio parahaemolyticus,Shigella and Bacillus cereus. This study optimized the microwave-assisted extraction technology of pitaya peel pigment. The obtained extract has good antioxidant activity and strong antibacterial activity against common food-borne pathogens.