▎ 摘　　要

NOVELTY - Preparing purple sweet potato pigment, comprises e.g. (i) washing the fresh purple potato, drying until there are no visible water droplets on the surface, and cutting into purple potato strips by hand or machine, (ii) using the acidic aqueous solution as the extractant, adding the extractant to the purple potato strips, and crudely extracting the purple potato anthocyanin pigment from light to obtain a crude pigment extract of the first grade, (iii) subjecting purple potato strips to freeze-thaw treatment, i.e., freezing-thawing-adding extractant extraction-purple potato strips, and freezing-re-dissolving-re-extracting to obtain secondary pigment crude extract, (iv) combining the primary pigment crude extract and the secondary pigment crude extract, and performing vacuum concentration at a concentration temperature of less than or equal to 45 degrees C to obtain a pigment concentrate, and (v) preparing a graphene oxide dispersion, and adding the pigment concentrate to the graphene oxide dispersion. USE - The method is useful for preparing purple sweet potato pigment. ADVANTAGE - The method: does not utilize alcohol solvents; improves the extraction rate of pigments through freeze-thaw treatment; utilizes the adsorption of graphene oxide to remove impurities e.g. proteins; avoids the anthocyanin complexation; improves the purification effect; and prepares high-purity purple potato anthocyanin pigment. DETAILED DESCRIPTION - Preparing purple sweet potato pigment, comprises (i) washing the fresh purple potato, drying until there are no visible water droplets on the surface, and cutting into purple potato strips by hand or machine, (ii) using the acidic aqueous solution as the extractant, adding the extractant to the purple potato strips, and crudely extracting the purple potato anthocyanin pigment from light to obtain a crude pigment extract of the first grade, (iii) subjecting purple potato strips to freeze-thaw treatment repeatedly twice, i.e., freezing-thawing-adding extractant extraction-purple potato strips, and freezing-re-dissolving-re-extracting to obtain secondary pigment crude extract, (iv) combining the primary pigment crude extract and the secondary pigment crude extract, and performing vacuum concentration at a concentration temperature of less than or equal to 45 degrees C to obtain a pigment concentrate, (v) preparing a graphene oxide dispersion, adding the pigment concentrate to the graphene oxide dispersion, shaking and adsorbing, and centrifuging and separating, and taking the supernatant, (vi) packing macroporous adsorption resin into the column, injecting the supernatant into the macroporous resin layer at a sample flow rate of 3-3.5 bed volume/hour, (vii) rinsing the saturated macroporous resin layer with water, using an eluent to elute the anthocyanin pigment, and collecting the eluent, (viii) concentrating the collected eluate in vacuum at 40 degrees C or below, and evaporating the ethanol to obtain a purified pigment concentrate, and (ix) performing vacuum freeze-drying the purified pigment concentrate to obtain a dry product of purified purple potato anthocyanin pigment.