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Unformatted text preview: UNIVERSITY OF CALIFORNIA Department of Viticulture and Enology VEN 135 WINE TECHNOLOGY AND WINERY SYSTEMS 8. FERMENTORS Fermentors usually differ from general storage tanks in several ways. There are particular aspects which relate to the filling with must, handling of skins and temperature control that make the requirements of "red fermentors" somewhat different from those of "white fermentors". Ideally, fermentors should be designed and selected so that they are general purpose units and can handle both red and white musts. FILLING AND EMPTYING For red wine fermentations, the fermentor will be filled with must containing both juice and skins. As a result the diameter of the filling valve will usually be twice that of the corresponding valve for juice alone. Similarly, if this valve is to be used for emptying the skins by sluicing the skins out of the fermentor into a pomace pump, it should be at the lowest point of the base, and this is usually near the front door, especially for tanks with sloping floors. White musts can also be introduced through the "red must" valve (using a reducing fitting) or through the "racking valve". The racking valve should be positioned at approximately 10% of the fermentor height from the base. This valve will usually be smaller in diameter since it will be used for liquids with some suspended pulp only. It is often offset to one side of the front of the tank and will sometimes be aligned so that it is tangential to the tank wall rather than radially in towards the center of the tank. The racking valve will be used for wine removal from the tank and it is positioned up from the base so as to reduce the solids content from the "lees" at the base of the fermentor. In the case of the red fermentor, the racking valve will be used to draw juice/wine for the "pump-over" operations as well as the racking of the wine at the end of the fermentation. As the wine is drawn off, the skin cap will move down the tank until no more wine can be racked. Small and medium-sized red fermentors will usually have a second door, (outward opening) located at about the same height as the racking valve which will then be opened to assist the removal of the skins by manual means. In larger fermentors this is often replaced by a screw conveyor in the base of the tank to remove the skins. CONTACTING OF SKINS AND JUICE There are several alternative ways in which the juice and skins (and seeds) are mixed during red fermentations. The empirical (and scientific) evidence is that none of these has a bearing on the color extraction, despite some widespread misconceptions that they do. There is also no scientifically valid data showing any one approach capable of capturing more flavor or aromas than the other. The origins of these approaches are somewhat regional and hence often thought to be essential in making wines typical of that region. The alternatives include: (1) Pumping Over of Juice (2) Punching Down of Skin Caps (3) Using a Rotating Fermentor...
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- Spring '09
- Harshad number, Tank, Radial Distance, Punchdown