Orange press liquor is a by-product generated by the citrus processing industry containing huge amounts of natural phenolic compounds with recognized
antioxidant activity. In this work, an integrated membrane process for the recovery of
flavonoids from orange press liquors was investigated on a laboratory scale. The liquor was previously clarified by ultrafiltration (UF) in selected operating conditions by using hollow fiber
polysulfone membranes. Then, the clarified liquor with a total soluble solids (TSS) content of 10 g·100 g-1 was pre-concentrated by nanofiltration (NF) up to 32 g TSS 100 g-1 by using a
polyethersulfone spiral-
wound membrane. A final concentration step, up to 47 g TSS 100 g-1, was performed by using an osmotic distillation (OD) apparatus equipped with
polypropylene hollow fiber membranes. Suspended solids were completely removed in the UF step producing a clarified liquor containing most part of the
flavonoids of the original press liquor due to the low rejection of the UF membrane towards these compounds.
Flavanones and
anthocyanins were highly rejected by the NF membrane, producing a permeate stream with a TSS content of 4.5 g·100 g-1. An increasing of both the
flavanones and
anthocyanins concentration was observed in the NF retentate by increasing the volume reduction factor (VRF). The final concentration of
flavonoids by OD produced a concentrated
solution of interest for nutraceutical and
pharmaceutical applications.