Concentration and Rectification of Grape Must by Nanofiltration

Abstract

The assessment of grape must concentration and fractionation by nanofiltration was investigated for six membranes covering a wide range of hydraulic permeabilities, rejection coefficients, and the permeation of an Entre Douro e Minho (EDM) grape must and four model musts. Permeation fluxes and rejection coefficients of sugars and organic acids were measured for all membranes and different operating conditions. Permeation fluxes varied from 23 to 113 kg h⁻¹m⁻² for the lower sugar content model musts and from 8 to 80 kg h⁻¹m⁻² for the higher sugar musts. The EDM grape must permeation fluxes were similar to the fluxes of the higher sugar content model must, and the rejection coefficients of sugars and organic acids were higher than those for the model musts. For membranes NFT50, NF200, and NF270, a preferential permeation of the organic acids with respect to sugars was verified. This effect was enhanced with the increase of sugar content of the model musts. These results endorse nanofiltration as a process for the concentration/rectification of grape musts upon the variation of the membrane characteristics and the nanofiltration operating conditions.