Different pre-extraction techniques were used aiming at increasing juice yield of O. macrorhiza fruits, the content of bioactive compounds such as flavonols and betacyanins, and consequently antioxidant activity of the produced juice. In comparison to untreated fruit's mash, the mash was treated prior to pressing with four pre-extraction techniques, (1) pulsed electric field (PEF), (2) thermal treatment using microwaves, (3) enzymatic treatment with commercial pectolytic enzymes, and (4) a combination of thermal and enzymatic treatments. The mashes treated enzymatically or by combination of thermal and enzymatic treatments produced higher yields of the juice, while the amount of juice from the untreated mash showed the lowest yield. Although all treatments led to no significant differences in total content of betacyanins, all treatments provided significantly higher contents of flavonol glycosides compared to the untreated mash. In addition to flavonols and the high contents of betacyanins, O. macrorhiza juice is rich in vitamin C. Consequently the juices produced from O. macrorhiza fruits had high antioxidant activity. The juice produced from mash treated enzymatically was preserved by three preservation technologies: Pulsed Electric Field (PEF), High Hydrostatic Pressure (HHP), and Pasteurization. Antioxidant activity of pasteurized juice was slightly lower than juices preserved by PEF and HHP techniques.
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