Nanofiltration process as non-thermal alternative to thermovinification in Pinot noir winemaking

This study aimed to evaluate the potential of membrane technology to improve polyphenol extraction during red wine alcoholic fermentation of the Pinot noir grape variety. The effect of adding permeate obtained from saignee nanofiltration onto grape pomace during alcoholic fermentation on wine phenolic extraction was investigated. The process consisted in the addition of nanofiltration permeate (NF) from saignee onto grape pomace in three different steps during alcoholic fermentation, corresponding to volumic mass of 1.060, 1.030 and 1.000 g.cm(-3) (treatments called NF1060, NF1030 and NF1000, respectively). This innovative extraction strategy was compared with the extraction by thermovinification (TV), a conventional method used to increase anthocyanin extraction in red winemaking. All trials were performed at microvinification scale (30 kg of grapes, in duplicate). Total polyphenol index, color intensity and total anthocyanins were measured during fermentation. In the finished wines, after malolactic fermentation, tannins, HCl index, gelatin index and dialysis index were determined and a sensory evaluation was made by an expert panel. The results show that nanofiltration treatments were able to extract the same amount of total polyphenols and reach the same color intensity as thermovinification. A higher extraction of anthocyanins (around 25 %) was obtained using NF1030 and NF1000, and a higher content of tannins was found in NF wine than TV wine, with a higher degree of polymerization in NF1060 and NF1030. The perceived astringency reflected the gelatin index values, with NF1030 wine the least astringent. The wine tasters agreed on a higher sensory appreciation for NF wines, especially NF1030. The results obtained in this study are a good incentive to promote research on nanofiltration processes as a non-thermal alternative to modulating polyphenol extraction during red wine fermentation.