Flavedo and albedo of five citrus fruits from Southern Italy: physicochemical characteristics and enzyme-assisted extraction of phenolic compounds

Peels are major byproducts of the juice processing industry. Citrus peels are composed of two tissues, namely the flavedo (outer layer) and the albedo (inner layer). Here, flavedo and albedo were obtained from the peel of grapefruit cv. ‘Star ruby’, lemon cv. ‘Akragas’, and sweet orange cvs. ‘Tarocco’, ‘Sanguinello’ and ‘Moro’. Freeze dried flavedo and albedo were investigated for their functional properties, and subjected to enzyme-assisted extraction with pectinase and cellulase (concentration of 6 U g−1 DW) to extract the phenolic compounds. Albedo showed superior physicochemical characteristics than flavedo. Albedo from ‘Tarocco’ exhibited the maximum water holding capacity (10.9 ± 0.48 g/g). Grapefruit albedo revealed the highest water swelling (13.4 ± 2.62 mL/g) and oil binding (6.31 ± 2.62 g/g) capacities. As regards the enzyme-assisted extraction of phytochemicals, both enzymes enhanced the extraction of phenolics (p < 0.05) compared to the controls. In flavedo, pectinase and cellulase increased the recovery of phenolics by approx. 30%, whereas in albedo the yields were increased above 60%. Results from this investigation suggest that albedo might be used by the food industry as a novel raw material, due to its superior physicochemical properties. Moreover, results provide evidence that the enzyme-assisted extraction is advantageous to recover phenolics from the citrus peels.