Although it is generally referred to as a grape crusher this reference should also include “destemmer” or “destalker” seeing that this equipment is usually used to destem the grapes and break or crush the berries.
|The destemming part of the equipment consists of a perforated drum, with an axis and beaters inside the drum, as illustrated in Figure 1. The drum is usually made from stainless steel and the beaters can be made from stainless steel or other inert material. After the grapes are transferred from the hopper of the crusher it moves to the
rotating drum, where the berries are beaten from the stems by the beaters that move into the opposite direction of the drum. The berries fall through the perforations of the drum to the rollers of the crusher where the berries are broken. As a result of the position of the beaters on the axis the stems are moved to the outside of the drum from
where they are moved or blown to the outside of the cellar. Grape stems contain many tannins. Tannins cause the astringent taste when stems are chewed. If stems are consequently crushed with the berries it will cause an astringent taste in the resulting wine. It is consequently important to destem the grapes before it is crushed, therefore the two processes are separated in the grape crusher and destemming is always done first. FIGURE 1. The rotating perforated destemmer of a destemmer-crusher. The crushing part of the equipment consists of two splined rollers rotating in opposite directions, as indicated in Figure 2. The berries falling through the holes of the perforated drum of the destemmer are broken by the rollers in order to set free the juice. The distance between the rollers is important and can be set. If the distance is too wide the berries of cultivars with small berries will not be crushed and if it is too narrow the berries will not only be broken but crushed and the seeds also broken. This may cause that more flesh and skin particles end up in the juice that will increase the lees percentage of the juice. The broken seeds can also cause more bitterness and astringency in the resulting wine.
Different safety hazards exist during the crushing and destemming of grapes. Due to the breaking of the berries, the floor surface will be slippery and cellar workers must walk carefully in this area. The crusher is driven by an electric motor and driving belts. Workers must be very careful around exposed electric cables and moving belts. There are also various moving metal parts and these must at all times be covered correctly with safety plates. Fingers and hands must be kept away from these moving parts. Depending on the locality of the equipment the noise may be excessive in which case the necessary ear protection must be worn.