Extraction and preliminary purification of anthocyanins from grape juice in aqueous two-phase system

• Ethanol/NaH2PO4 ATPS was used for extraction and preliminary purification of GA.
• The feasibility and efficiency of the ATPE of GA were proved.
• Effects of ATPS compositions on the stability of GA were investigated.

Aqueous two-phase extraction (ATPE) was employed for the extraction and preliminary purification of anthocyanins in grape juice (GA). The influences of such factors as the type and concentration of salt, the concentration of alcohol and the quantity of grape juice, extraction time, system pH and temperature were investigated to obtain the optimal extraction conditions. They were listed as follow: sodium dihydrogen phosphate (NaH2PO4) concentration 28% (w/w), ethanol concentration 25% (w/w), the quantity of grape juice 1 mL, temperature 298.15 K, time 1 h and no pH adjustment. Under the optimal conditions, the relative and absolute recovery of GA in the top phase reached 99.35% and 99.26% in one step, respectively, while the sugar-removing rate reached 75.08%. The results of Multistage and scale-up extractions showed that it could remain over 90% GA in the top phase and remove more than 90% sugars after continuous extraction for two times. Scale-up extractions and the GA stability results showed the effectiveness and great potential of this method in processing mass grape juice.

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