Pressing-Clarification of White Grape Must
In winemaking, lees are solids-containing mixtures that have been separated from juice or wine by gravity settling, flotation, centrifugation, or other techniques. The solids can include grape material, tartrate precipitates, yeast cells, fining agents, and oak chips. Typically, the largest volumes of lees come from the grape. In white winemaking grapederived solids are mainly removed prior to fermentation, whereas in red winemaking they are usually removed after fermentation when they are combined with yeast.
Three types of filters are used for lees filtration: plate-andframe filter, rotary vacuum drum filter, cross-flow filter, or by centrifuge (Chapter 12). Plate-and-frame filters are easier to use than rotary vacuum filters - especially for small wineries. They also have the advantage of not exposing the juice to air. Minimizing oxidation can have a significant impact on resulting wine quality.
Rotary Drum Filter
Rotary drum vacuum technology is the standard for large wineries and for the major mobile services (Figure 4.10). This approach utilizes a stainless-steel drum with a screen on the outside and a partial vacuum on the inside; the drum is coated with a layer of diatomaceous earth (DE, kieselguhr) that provides the filter medium. The bed of DE has to be built up by re-circulating the juice and adding more DE.
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