Resource and Energy Efficient Method of Dried Fish Production

Abstract

The authors of the article propose a method of convective dehydration of fish products, which has an intermittent nature of implementation. The dehydration process consists of the continuous initial phase and following combined periods consisting of phases of drying and relaxation of dehydrated surface layer of the raw material. The necessity of applying relaxation is due to the fact that during the drying process the surface layers that have lost some of the moisture are significantly densified. The size of the capillaries for moisture passing through the surface layers is reduced. Near the surface a layer is formed, which lacks the significant mass of moisture and has low diffusion properties. As a result, the dehydration process of the entire sample slows down. The rational use of relaxation leads to restoring the moisture-conducting properties of the surface layer of fish. The supply of electrical energy to the heating elements is stopped during the relaxation. The minimum circulation rate of the drying agent is maintained in the drying installation. Fresh air with a lower temperature and higher relative humidity than the drying agent is supplied to the drying agent. The conditions in the drying installation restrain external mass transfer and facilitate to the relaxation of the dehydrated surface layer, that is, to the redistribution of moisture in the thickness of the fish. The proposed method of dehydration of fish raw material reduces the cost of electric energy in the production of dried products and provides more rational coolant usage. The final fish products have more attractive appearance due to reduction of tissue deformation as a result of applying the relaxation of dehydrated surface layer.