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Nowadays, the recovery and purification of bioactive molecules from food processing streams has gained a great interest in both producers and customers due to their anti-microbial, anti-oxidant or anti-carcinogenic activity. Therefore, efficient recovery of fine bioactive chemicals and/or production of added-value products appear to be a new frontier in agro-food waste valorisation. Membrane processes have become key separation technologies in the food processing industry over the last 35 years. Based on their intrinsic characteristics and key advantages over conventional methodologies, these processes offer also a great potential for the exploitation of agro-food wastes. This article discusses the use of membrane processes for the recovery, concentration and purification of compounds with target bioactivity from agro-food process streams and residues. Case studies related to the treatment of citrus, olive oil and artichoke by-products, investigated on both laboratory and industrial scale, are analyzed and discussed, highlighting technological advances and improvements over conventional methodologies.

The influence of ultrafiltration on antioxidants and the total antioxidant activity (TAA) in blood orange juice using the tubular polyvinilydenfluoride (PVDF) membrane was studied in the paper. The results indicated that about 85% of both ascorbic acid (Vc) and anthocyanins content remained during ultrafiltration of blood orange juice. Retention of the other antioxidants such as hydroxycinnamic acids and flavonoids, except for querecetin, were more than 90%. Compared with the fresh blood orange juice, a loss of 23% of TAA in the pasteurized juice was observed, while a loss of 10% in ultrafiltered juice, which was mainly attributed to the loss of ascorbic acid and anthocyanins content.

Clarification of blood orange (Citrus Sinensis) juice by ultrafiltration was studied using the tubuir PVDF membrane. The results indicated that the clarified juice was very clear with the trasmittance of 96.9%. Vc could be highly retained in the clarified juice, and the juice color and flavor were kept quite good. The effects of operating conditions on the permeate flux were also studied, and the influence of ultrafiltration on antioxidants and total antioxidant activity in blood orange juice were determined.