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At arrival of the mushrooms at the factory, the mushrooms are washed immediately. Therefore the mushrooms are put into a washing-flotation unit. Due to the flotation of the water, the mushrooms are transported to the other side of the washing installation. Friction between the mushrooms and between water and mushroom removes impurities. Sometimes air is injected to increase the effectiveness of the washing.
To increase the durability of the mushrooms, they are blanched. Blanching is a short heat treatment (maximum of several minutes) at a high temperature (98ºC). Blanching inactivates enzymes which can spoil the mushrooms. Injection of steam makes it possible to reach a high temperature fast. Blanching at a high pressure, 3-4 bar, increases the effectiveness even more.
During the washing and blanching the mushroom can absorb a lot of water. The drip water is unwanted during the next cutting process. This water can be removed with a dewatering shaker. Therefore the mushrooms are being transported over a stainless steel plate which shakes. The water can be removed through holes in the dewatering shaker.
After draining the mushrooms can be sliced. Via slots the mushrooms are being positioned and all sliced in the length of the mushroom. The mushroomslices are T-shaped. The knives consist of circular knives, called slicerheads. The distance between the knives determines the thickness of the mushroom slices.
After slicing, the mushrooms are cooled. In ice water the mushrooms are cooled fast. Cooling by means of counter-current flow increases the effectiveness.
After the cooling the mushrooms can again absorb a lot of water. When the mushrooms are packed in a jar or tin with fluid this drip water is not a problem. When the mushrooms are to be frozen this drip water is unwanted. The water can be removed with a second dewatering shaker.
Jar and tin
Next process step is the packaging of the mushrooms. Generally the mushrooms are packed by weight. This means an equal weight of mushrooms in every jar or tin. After the filling of the jars and tins with mushrooms brine or acid can be added. Brine or acid increases the shelf life of the mushrooms.
To give the mushrooms a longer durability, they are pasteurised or sterilised in the packaging. Pasteurisation is a less intensive heat treatment than sterilising. With sterilisation all micro-organisms, also the spores, are killed. Brine or sour prevents spores to develop into vegetative cells which can grow. An intensive heat treatment is therefore not needed. The shelf life after pasteurisation (in combination with brine/sour) or sterilisation can be more than one year.
Freezing to -5ºC
After the draining the mushrooms are frozen individually. Therefore they are placed on a large plate or conveyor belt and frozen seperatly from each other. Freezing can take place in a batch or continuous process. By freezing the mushrooms fast the structure remains firm and the mushroom slices do not stick together. In this freezing step the mushrooms are quick frozen to a temperature of -5ºC.
The quick frozen mushrooms are generally packed in plastic bags.
Freezing to -20ºC
The mushrooms are being frozen to -20ºC after packing. Because the mushrooms are already quick frozen to-5ºC, deep freezing is less critical. However the quality remains better if the total freezing time is as short as possible. Unblanched frozen mushrooms have a shelf life of several months. Blanched frozen mushrooms have a shelf life of several years.
At arrival of the mushrooms at the factory, the mushrooms are washed immediately. Therefore the mushrooms are put into a washing-flotation unit. Due to the flotation of the water, the mushrooms are transported to the other side of... volle Beschreibung