Separation of ethanol and polyphenols from red wine by diananofiltration

In the present study NF-based diafiltration runs - single, sequential diaNF/RO process and two- stage diafiltration configurations are investigated in order to check the separation ability towards ethanol and the polyphenolic fraction in red wine Mavrud. Two nanofiltration (Alfa Laval NF99HF, Microdyn Nadir NP030P) and one reverse osmosis (Alfa Laval RO99) membranes are investigated. Due to the high permeate flux and rejection coefficients difference, NF99HF has been most effective for the purposes of moderate wine dealcoholization and high retention of the selected groups of bioactive compounds. From the second step in the sequential diaNF/RO process two outflows with substantially different ethanol content are obtained. Recycling either of them results in a different two-stage diafiltration configuration, whose performance is strongly affected by the number of diavolumes regarding the low-molecular solute; variation of the operation parameters may imply different membrane areas and/or transmembrane pressure in each membrane stage. In the dealcoholization of Mavrud red wine, sequential NF99HF(dia)/RO99 filtration has been successfully used, effectively preserving the bioactive compounds from the group of polyphenols and anthocyanins, as well as the antioxidant activity of the final wine (up to 5 % loss of ORAC activity was measured).