Recovery of bruteridin and melitidin from clarified bergamot juice by membrane operations

Four commercial spiral-wound membranes with nominal molecular weight cut-off (NMWCO) from 150–300 to 3,500 Da were tested in order to evaluate their performance in the recovery of brutieridin and melitidin from clarified bergamot juice. Filtration experiments in batch concentration mode were performed on a laboratory filtration membrane equipment in selected operating conditions up to a weight reduction factor (WRF) of 5. The performance of selected membranes was evaluated in terms of permeate flux and rejection coefficients for melitidin, brutieridin, glucose, fructose, and sucrose. Experimental results indicated that the rejection of selected membranes toward melitidin and brutieridin was strictly correlated to their NMWCO. Among the selected membranes, the Desal GE membrane (NMWCO 1,000 Da) offered the best performance in terms of separation between sugars and brutieridin/melitidin in the clarified juice with high retentions toward flavonoids (>67% for melitidin and >82% for brutieridin) and lower retention toward glucose (21.9%) and fructose (10.6%). Practical applications: Bergamot (Citrus bergamia) juice has not found a real use in the food industry due to its bitter taste and it is considered a waste of the essential oil production. On the other hand, flavonoid diglycosides of the juice, such as brutieridin and melitidin, have been recently recognized for their hypocholesterolemic action. The proposed membrane-based technology offers a valid alternative to the use of conventional purification methodologies for the recovery of this phenolic fraction from the clarified juice and its reuse for the production of fortified juices and functional foods.