Dewatering

Usually a process for water removal can be split into two: drying and dewatering. Drying processes usually involve the addition of heat for water evaporation, whereas dewatering usually involves little or no application of heat.

Water is bound to the structure of a food product in several ways. The most important of these are chemical and mechanical binding which vary a lot in strength. Usually the water that has the weakest binding can be removed by mechanical dewatering or without the application of heat. Dewatering has some advantages compared to thermal drying. In general, as much water as possible should be removed non-thermally before the remaining water in a product is removed in a dryer to bring the water content down to a specified level. As little, if any, heat is applied to a product during dewatering, this leads to positive quality effects. The more water that is removed without applying heat, the better the quality of the end-product. This is especially important for temperature-sensitive products, such as fatty fish and seafood products. Another advantage of dewatering is that it is much less demanding in terms of energy compared to thermal drying. Most drying processes involve large amounts of drying air to remove the stream of moisture from the product. In many industries this stream of air has to be cleansed to remove pollutants. This problem is reduced by using dewatering prior to thermal drying.

SINTEF's team of specialists at the Dewatering Laboratory work both on dewatering and drying. Typical challenges that many companies face is how to use a dewatering process for partial water removal for a specific product? How much water should be removed by dewatering? What kind of thermal dryer is most efficient for removing the final part of the water? When finding the answers, SINTEF can draw up the design criteria for an optimal dewatering route for the product in question. The Dewatering Laboratory has a range of dewatering processes on hand, such as different kinds of presses, centrifuges and three filtration techniques: ultrafiltration, membrane filtration and reverse osmosis.

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