Nanofiltration and reverse osmosis in winemaking

The paper is an overview of the application of membrane processes to winemaking. The aim is to present both the application of membrane processes in winemaking and a general philosophy of their development from a process engineering point of view. Several examples illustrate this approach, in particular applications of nanofiltration and reverse osmosis membranes, but the other techniques such as microfiltration, ultrafiltration and electrodialysis are also mentioned. The principal condition for further development of membrane processes in winemaking is a good understanding of membrane techniques, separation techniques and characterisation of the membrane itself and the product (must or wine) to be filtered. The last constrain, given the complexity and variability of must and wine composition, is not trivial and needs a considerable effort at both industrial and research levels. For the same reasons, the coupling of the membrane and other physico-chemical treatments appears to be a promising research domain.

The possibility of coupling several membrane techniques enables numerous new applications. It cannot be realised without a good knowledge of the membranes themselves, the transfer phenomena and the separation mechanisms. The reduction of sugar content in the must is a good example: that process represents an innovative solution, applying a well known technology. The treatment has the following advantages: • The risk of stuck fermentation is limited and it helps the winemaker have better control of extraction phenomena during vatting.