Pitaya peel pigment extraction method

The invention discloses a pitaya peel pigment extraction method. The method comprises the steps of pretreatment, organic matter extraction, complex enzyme dissolution, sodium alginate adsorption and purification, and evaporation, drying and concentration. By utilizing the characteristics that pectin and fibers are insoluble in an organic solvent and betacyanin is soluble in the organic solvent, preliminary separation of betacyanin from pectin and cellulose is realized, and photooxidation of separated betacyanin can be avoided by soaking betacyanin in a dark environment; a compound enzyme is added into the mixed solvent to promote enzymolysis of pectin and fibers in the mixed solution so as to further separate out betacyanin and dissolve the betacyanin into the organic solvent, and the mixed solution is filtered to obtain an extracting solution dissolved with betacyanin; sodium alginate is added into the organic solvent dissolved with betacyanin, so that pectin in the extracting solution is further condensed a