Comparative study of red grape must nanofiltration: Laboratory and pilot plant scales

Abstract A consequence of global warming is the early ripening of grapes which promotes, among others, a higher fermentable sugar (glucose and fructose) content. This leads to wines with an alcoholic degree higher than desired. In this work, the main differences between red grape must nanofiltration at laboratory and pilot plant scale were studied in order to perform the scale-up of a nanofiltration process to reduce the sugar content. For this, previous results of the nanofiltration of commercial red must using the SR3 membrane in a flat sheet crossflow module were compared with those obtained for the filtration of natural red must using the same membrane in a spiral wound module at two different applied pressures. The aim of this publication is to analyze the main differences between red grape must nanofiltration at laboratory and at pilot plant scale. Results showed that the flow destabilization and eddy promotion caused by spacers in the spiral wound module mitigate the rate at which the cake thickens and compacts on the membrane surface. This causes a less sharp flux decrease, less variable sugars rejection and osmotic pressure difference. Moreover, higher applied pressure promotes a higher membrane fouling and osmotic pressure that worsen the flux decay.