An Eco-Friendly Integrated Membrane Process for the Concentration and Purification of Functional Bioactive Compounds from Citrus Hybrid Tacle® Extract

Tacle is a tangerine-like citrus obtained from the crossbreeding of Clementine and Tarocco cultivars. The extract of this fruit is rich in polyphenol glycosides, mainly naringin and hesperidin, and other bioactive phytochemicals typical of Citrus fruits (such as carotenoids). These compounds are well recognized for their protective activity against oxidative agents involved in several degenerative disorders. Developing sustainable and effective purification procedures of bioactive compounds from vegetable sources has always been a challenging task for scientists. In this work, an eco-friendly process based on a combination of pressure-driven membrane operations and osmotic distillation has been investigated, for the first time, to purify and concentrate functional biomolecules in tacle extracts. In the first step, a concentrated stream rich in carotenoids was obtained by using hollow-fiber ultrafiltration (UF) membranes according to a batch concentration-diafiltration mode. The selected membranes showed a retention towards b-carotene higher than 98% and lower than 5% for polyphenols and sugars. In the second step, nanofiltration (NF) membranes in spiral-wound configuration were tested in order to produce concentrated fractions enriched in flavonoids and depleted in sugars. Membranes with molecular weight cut-off (MWCO) of 300-500 Da showed a sugar removal efficiency from the clarified extract (permeate UF+diafiltrate) of about 65%; on the other hand, more than 85% of flavonoids were rejected. A further concentration of the NF retentate was achieved by a final step of osmotic distillation (OD). According to the investigated process, three valuable and innovative fractions were obtained: i) a UF retentate fraction rich in carotenoids useful for cosmeceutical formulations, food supplements or as natural colorant; ii) a NF retentate rich in flavonoids of interest for pharmaceutical applications due to its anticholesterolemic activity; iii) a purified fraction enriched in sugars and salts suitable for drinking formulations.