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Pore size distribution is one of the most important characteristics of a membrane.This can be obtained from the fitting of pore radius calculated from retention versus flux measurements for a set of solute solutions. In this work a set of non-charged similar molecules are chosen as solutes to minimize other interactions apart of those related to size. The hydrodynamic model will be used to characterize the behavior of the membrane to uncharged solutes, assuming that membrane pores are straight and cylindrical.As is known, the phenomenon of concentration polarization must be taken into account because true retention is not experimentally accessible by concentration measurements. Frequently, the film layer model is applied for the dependence of

2011) Sugar reduction in white and red musts with nanofiltration membranes, Desalination and Water Treatment,[167][168][169][170][171][172][173][174] To link to this article: http://dx. A B S T R AC TIn recent years the alcohol content of wine increases mainly due to climate change. Moreover, at present, consumers are increasingly demanding more aromatic and less alcoholic wines, it is due to the greater social awareness in the alcohol consumption and the regulations of the alcoholic products. The aim of this work is the reduction of sugar in the grape must to obtain wines with a slight reduction of their alcoholic degree. A reduction of sugar has been by performing two successive stages of nanofi ltration. To this end, we have worked with two types of musts: one from the Verdejo variety of white grapes and the other from red grapes of the Tinta de Toro variety. Each must has been fermented both after treatment and, to be used as control, without any fi ltration in order to check the effectiveness of the process. Once fermentation is completed, wide-ranging analysis have been used to study all possible changes in the characteristics of the wine from a chemical point of view. The alcohol reduction reached by the wines obtained after nanofi ltration and mixing of both white and red musts has been satisfactory.

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Climate changes are inducing increased sugar levels of must, which produces negative effects on wine quality, as unbalanced wines with high degrees of alcohol. So, effective strategies to control the increase of sugar levels in must have been studied. One of them is the use of a membrane process, and this is applied in this work. The sugar level of white must from Verdejo (Vitis vinifera variety) was reduced using diverse membrane processes, and the effect of this fact on the volatile composition of the corresponding wines is studied. The study was carried out during three consecutive vintages. An important impact of the reduction of sugar levels of must on the volatile composition of the obtained wines was detected, which was due to some retention phenomena of aromatic and precursor compounds. To minimize the volatile composition modifications, an appropriate selection of the nanofiltration membrane must be done.