This could
be attributed to the concentration polarization, i.e., concentration
of compounds on the membrane surface, and fouling of membrane, which was a behavior similar to that reported
by Díaz-Reinoso et al. (2009) in the nanofiltration of aqueous
extracts from distilled fermented grape pomace. In this
present work the average flux was 22.8 L/h m2, a value in accordance
with Banvolgyi et al. (2006) and Mello et al. (2010), who
subjected red wine and propolis extract to nanofiltration and
obtained flux values of 20 L/h m2 and 25 L/h m2, respectively.
Ferrarini et al. (2001) noted variation of the permeate flux
from 7.4 to 5.4 L/h m2, in grape juice, while Vincze et al. (2007)
obtained a permeate flux varying from 14 L/h m2 to 4.6 L/h m2
of sea buckthorn juice.