Filtration Methods in Winemaking
Filtration has long been an important step in the winemaking process for wineries of all sizes around the globe. This process helps achieve the best possible texture, taste, consistency and stability of wines before they are bottled for distribution and sale to consumers. Various types of filtration methods are still used today, and there are likely to be numerous improvements in wine filtering techniques and practices in future years. Just as there are major differences in wines produced by different wineries, there are often important variances in techniques used to achieve certain flavours, bouquets and full-bodied qualities of different wines.
Filtration Methods and Techniques Commonly Used in Winemaking Today
Commonly used filtration methods and modes by many wineries throughout the world today include the following:
- Earth Filtration. – In earth filtration, the filtering medium is diatomaceous earth (D.E.), which is also known as diatomite or kieselgur (kieselguhr), a soft sedimentary rock that can be easily ground or crumbled into a whitish powder. This substance is used as a coating on filtering screens or pads prior to the filtration process. It is also employed to help ensure even and ongoing feed of wines-in-process during the cycle of filtration. Earth filtration requires two distinct phases: (1) Pre-Coating, during which a covering of coarse-textured earth is placed on a screen composed of stainless steel or nylon, and (2) Filtration, when a mixture of earth and wine are poured through the screen, creating a seamless flow of the mixture to be filtered. Some earth filters have supportive plates. Others have rotary vacuum filters, or a drum that rotates. The wine is vacuum-sucked via a pump through these rotary vacuum filters.
- Pad Filtration. – During Pad Filtration, wine runs across a filtering pad composed of cotton, cellulose, D.E. or man-made fibers like polyethylene. This filtration method makes use of absorption, screening, sedimentation, turbulence and inertia to complete the wine filtration process.
- Membrane Filtration. – This mode of filtering wine makes use of a cartridge composed of such materials as nylon, polypropylene, cellulose esters or glass fibres. Making heavy use of screening techniques, some depth filtering is also included in the process. Although Membrane Filtration may have some effect on clarification, this technique is used primarily for microbial stabilisation of wines. It is frequently the final filtration step before wines are bottled for sale and consumption.
- Cross-Flow Filtration. – During the Cross-Flow Filtration method, wine runs forcefully across the surface of a membrane that is porous, creating sufficient pressure to push the wine through the porous membrane surface. While the wine is pumped within a partly enclosed pathway, its level of concentrated particles grows, producing wine with highly concentrated particles in its body. This type of filtration is also appropriate for reverse osmosis.
- Ultra-Filtration. – This form of wine filtration involves a cross-flow method employing a membrane having a count of nominal relative weight cut-off per molecule of 10,000. This process will rid the wine of proteins and any sizable phenolics, enhancing its flavour and degrees of stability.
- Ceramic Membrane Crossflow. – This new wine producing technology will most likely make batch processes for winemaking obsolete in the near future. Its updated pressing techniques supply free-run juices with as much as one percent floatation of solids along with a cross-stream of white juice in an ongoing process. This advanced technique for wine production will also most certainly render centrifuging of wines-in-progress a method of the past.
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