Sensory and Chemical Effects of Cross Flow Filtration and Pumping on White and Red Wines

In the world of modern vinification, cross flow filtration and pumping are widely used. In the absence of systematic studies examining the effects of these unit operations on the resulting wine, winemakers are sometimes reluctant to use them to process their wines. Because cross flow filtration can not be accomplished without pumping, both of these unit operations were studied.;Cross flow filtration is an increasingly common post-fermentation process in the wine industry. Because of the nature of the membranes used in this process, our hypothesis was that cross flow filtration would not have a significant impact on the sensory or chemical properties of either white or red wines. To investigate this, a California white wine blend and a California red wine blend were filtered in three 570 L lots using a Bucher Vaslin cross flow unit with a nominal 0.22 micron polyethersulfone membrane. The unfiltered control was sent directly to the bottling line without filtration. Panelists evaluated the wines nine times during an eight-month descriptive analysis panel with replicated tasting at each time point. UV-VIS spectrophotometry and the Adams-Harbertson assay were used to determine color and phenolic content of the filtered and unfiltered wines respectively. The effect of filtration was found to be significant for one sensory attribute out of 16 total measured in the white wine. Similar analysis for the red wines indicated that six sensory attributes were significantly different out of 16 total in the red wine. Unfiltered red wines were found to be higher in earthy, grassy, oak, and smoke aromas compared to filtered wines and lower in mixed berry and stone fruit aromas compared to the filtered wines, but only after two months in bottle. Cross flow filtration was found to have a stabilizing effect on the sensory profile of both wines. For both red and white wines, there were significant changes in color and phenolic profile with filtration, but it is not clear, especially for red wines, that the changes in phenolic compound concentration were large enough to be detected sensorially.;The transfer of must, juice, and wine is a necessary process in vinification at various points from grape receiving through bottling. Pumps are among the most important pieces of equipment used to move wine from one place to another in commercial wineries. However, there has been a general lack of systematic data generated to assess the effect of pumping on the chemical and sensory properties of wine. These effects, if found, could be due to oxygen pickup during pumping, or some other mechanism of converting mechanical energy to changes in wine composition. To investigate this, a white wine blend and a red wine blend were pumped through a closed loop system at two different run times. Three different pumps were used in the experiment, a centrifugal pump, a flexible impeller pump, and a progressive cavity pump. This resulted in six treatments each for the white and red wines. The entire experiment was carried out in duplicate. A full sensory descriptive analysis panel was conducted on the wines using a ballot-trained panel. UV-VIS spectrophotometery and the Adams-Harbertson assay were used to determine color and phenolic content of the pumped and unpumped wines, respectively. Panelists were not able to differentiate pumped wines from the control, and additionally progressive cavity, flexible impeller, or centrifugal pumped wines from each other. Although statistically significant color differences were found between red wine treatments, these differences were less than 2% and no statistically significant phenolic differences were observed. Oxygen pickup was observed in the progressive cavity pump treatment, but relatively little was observed in the flexible impeller or centrifugal pump treatments. In summary, pumping caused little to no chemical or sensory changes in the experimental wines.