Solids Reduction

Some portion of the pulp and other solid materials of the grapes will be suspended in the juice after the grapes are pressed. These solids are removed from the juice to prevent the unwanted bitter flavor characteristics they can cause from remaining in the juice. This is especially true of white and rosé wines as they are pressed prior to fermentation and are lighter flavored wines that do not contain the large levels of tannins that contribute to red wine flavor and mouthfeel. Several techniques have been developed to remove solids from the wine. The most commonly used one is simply to chill the juice down and let gravity settle the solids to the bottom of the tank the wine is stored in. The low solids juice is then racked to a separate container. This technique is called cold settling and racking. The remaining lees is either discarded or given a very course filtration to recapture the liquid that remains with the lees. Solid levels for white and rosé wines are typically reduced to below 1% in solution. The fining agent bentonite is occasionally added to aide in the settling but it can cause a decrease in available nitrogen as it removes protein compounds from solution. Yeast nutrients should be added to juices in which bentonite was used before fermentation.