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The potatoes are brought from the land to the factory. When they arrive they still hold a lot of dirt to it. The method of washing is determined by the nature of the dirt and the end product. Generally, raw potatoes are sold with their skin. These potatoes are peeled by the consumer. It is enough to spray the the dirt of the potatoes with water. They can also be washed by placing them in drums with brushes. The drum spins around and the brushes remove the dirt of the potatoes.
When very clean potatoes are wanted they can be cleaned under high pressure. Very clean potatoes are used in for example cut products or potatoes that are eaten with their skin. The potatoes are put in a container of water. Water is sprayed with high pressure on the potatoes by means of sprayers in the sides of the container. In this way, all dirt is removed from the potatoes.
There may be still stones between the potatoes. These stones are not wanted and besides that, the peeling machine is not able to take these stones. These stones are removed with the help of a de-stoner. Potatoes are put in a tube-shaped tank
. The stones sink lower into the tube due to the difference in density between stones and potatoes. The de-stoning can happen in a batch as well as in a continuous process.
After the cleaning the potatoes are ready to be peeled.
The potatoes can be peeled by putting them in a drum with perforated sides. The skins are removed due to the friction with the sides and the friction between the potatoes themselves. The skin is removed from the drum through the perforations in the sides.
Another possibility is steam peeling. The potatoes are steamed with supersaturated steam by which the skin peels off. In a drum the skins are separated from the potatoes.
After the peeling of the potatoes they are (for a second time) put in a brushing machine. In this way, possible present black spots are removed.
The potatoes are washed to remove the remainders of the skin and the starch. The skins that cling to the potatoes are removed by a jet of water. During the peeling of the potatoes the cells of the potatoes are affected. The sticking starch of the cells is released. By spraying the potatoes sticking potatoes are avoided.
A visual control takes place after the potatoes are peeled, the spots are removed and the potatoes are washed. This control can happen completely automatically. Each potato is scanned separately. The potato is directly removed when irregularities are noted. This may be done by a pressing shaft or a jet of water.
Afterwards, the potatoes can be cut. The cutting process happens completely automatically. The potatoes can be cut in many shapes. Slices and fries are the most regular ones. The potatoes are transported through knifes in order to cut them. The knifes are placed in succession to enlarge the effectivity of cutting and to improve the cutting surface of the potatoes. By transporting the potatoes by means of running water the potatoes are put in the right position before the knifes.
Because new cutting surfaces are created when the potatoes are cut again cells are damaged and starch is released. The starch is washed away because the potatoes are transported with water.
To reduce the time of cooking, baking or frying of the consumer the products may be blanched. This means that the products are kept for a short time (a few minutes at most) in a high temperature (98°C). In blanching the germ count is reduced, the processing time is shortened and the enzymes are deactivated.
Raw and non-peeled potatoes are packed in open nets or open plastic bags. These potatoes are still alive and need oxygen. The potatoes decay faster if there is no oxygen on hand. Besides that, the storage life is longer when the potatoes are kept in a cool and dark place.
Peeled and processed potatoes are packed in closed plastic bags. They are often packed with a protective atmosphere. In general, the gas composition consists of a reduced oxygen content and an increased carbon dioxide content. Vacuum-packing is also used. Both ways of packing increase the storage life. The processed potatoes are to be stocked at fridge temperature.