Innovative approach for phenolic extract production from pomegranate by-products: Enzymatic liquefaction and ultrafiltration

The objective of this study was to separate the phenolic compounds that had been converted into free forms by enzymatic liquefaction (2% Viscozyme L+3% Pectinex) from the pomegranate by-products using ultrafiltration. The effect of two different molecular weight cut-off ranges (5 and 50 kDa) on phenolic content (total, free, bound), hydrolysable tannin content and antioxidant activity (total, free, bound) of the extracts was evaluated through a comparative analysis. The highest total phenolic content (89.45 ± 3.72 mg GAE/g), hydrolysable tannin content (20.31 ± 0.40 mg TAE/g), DPPH radical scavenging activity (476.18 ± 3.86 mg TEAA/g), ferric reducing antioxidant power (236.08 ± 2.03 mg TEAA/g) and cupric reducing antioxidant capacity (389.86 ± 0.65 mg TEAA/g) were determined in retentate of 50 kDa membrane. A strong correlation was observed between the phenolic content and antioxidant activity of samples. The separation of the sample using a 50 kDa membrane resulted in a slight concentration effect in the total and free phenolic content. Although antioxidant rejection of the 50 kDa membrane (118.77%, 125.52%, 127.00%) was lower than that of the 5 kDa (139.86%, 160.76% and 323.90%), the antioxidant concentrations of 50 kDa were higher compared to the concentrations of the 5 kDa (DPPH: 252.55 mg TEAA/g, FRAP: 183.39 mg TEAA/g, CUPRAC: 264.78 mg TEAA/g). These results may be associated with the compounds released by the enzymes, which have affected the membrane fouling by interacting with each other. Overall, this study suggests that the combined enzymatic liquefaction and ultrafiltration approach has potential as a green extraction method for sustainable separation of phenolic compounds from by-products. [Display omitted] •50 kDa showed a slight concentration effect on phenolic content.•Phenolic content of samples showed a strong correlation with antioxidant activity.•Compounds released by enzymes may have affected membrane fouling.•Enzymatic liquefaction and ultrafiltration can be used to separate phenolics.