Extraction of phenolics from citrus peels: II. Enzyme-assisted extraction method

The total phenolic contents of five citrus peels (Yen Ben lemon, Meyer lemon, grapefruit, mandarin and orange) extracted by enzyme-assisted aqueous extraction were evaluated using the Folin–Ciocalteu assay. The main parameters that affected the yield of phenolics include the condition of the peels, temperature of the extraction, types of enzymes, enzyme concentration and species of citrus. Generally, grapefruit peel had the highest total phenolic contents, followed by mandarin, Yen Ben lemon, orange and Meyer lemon peel. Cell wall degrading enzymes weakened or broke down the integrity of the cell walls of the citrus peels and eased the extraction. The highest recovery using Celluzyme MX in the enzyme-assisted extraction process was up to 65.5% (about 87.9% of the solvent extraction). The total antioxidant activity (using the FRAP) assay of the phenolics enzymatically extracted from different citrus peels were compared. The phenolics in grapefruit peels had the highest total antioxidant activity, followed by Yen Ben lemon, mandarin, orange and Meyer lemon.