Membrane sequences for fractionation of polyphenolic extracts from defatted milled grape seeds Original Research Article

Membrane technologies are presented as alternative techniques to purify and fractionate extracts from winery wastes with the aim of obtaining proanthocyanic fractions with different degrees of polymerization. These fractions, with the appropriate purity, have a great interest nutritionally and pharmacologically. To achieve different streams enriched in proanthocyanidins (PAs) with certain degree of condensation, several cross-flow filtration sequences using several polymeric membranes at different stages in the sequences were carried out. At the same time, several transmembrane pressures, concentrations and filtration designs (with or without diafiltration) were tested in tubular modules. A final sequence with four different membranes at the pilot-plant scale was achieved, which permitted us to obtain different fractions according to the molecular weight, some of them very pure in oligomeric PAs and, therefore, very interesting for the biotechnological industry. The raw material used in all cases was a hydroalcoholic extract from defatted milled grape seeds. Although no high yield was achieved in the whole process, the low value of this raw material (considered a waste in the winery industry) and the purity of the fractions obtained decrease the significance of the global yield.