A basket press (wine press) is a device used to extract juice from grapes during wine making. There are a number of different styles of presses used by winemakers but their overall function is the same. Each style of press exerts controlled pressure in order to extract the juice from the grapes. The pressure must be controlled, especially with grapes, to avoid crushing the seeds and releasing undesirable acids, tannins into the wine. Wine has been made at least as long ago as 6000 BC; recently a wine press was unearthed in Armenia with red wine dated 6,000 years old.
A basket press consists of a large basket that is filled with the harvested grapes. Once the 'free run' juice has been gathered, pressure is applied to the skins. This is very concentrated and has more tannins and pigments than the free run juice.
Pressure is applied through a plate that is forced down onto the fruit. The mechanism to lower the plate is often either a screw or a hydraulic device. The juice flows through openings in the basket. The basket style press was the first type of mechanized press to be developed, and its basic design has not changed in nearly 1000 years.
After pressing is complete, the remaining skins and debris called pomace, is often used to fertilize the vineyards, thus renewing the cycle of the vine to the bottle. The free run and press wine are kept separate during the subsequent fermentation and racking processes. At the winemaker's discretion, they may eventually be blended to make a wine with certain characteristics. Basket presses produce very high quality juice, but are labour intensive and expensive to use. They are ideal for small amounts of high quality wine.
When deciding on the size of press, remember it needs to be at least a quarter full in order to function efficiently. After the first pressing has finished it is necessary to empty out the pressed mash, crumble it and then press again; the extra volume of juice obtained from the second pressing is approx 15% of that from the first pressing.