1st Nordic Drying Conference - NDC'01, Trondheim, Norway, June 27-29, 2001

EFFECT OF PROTEOLYTIC ENZYME INHIBITOR ADDITION ON ENERGY CONSUMPTION IN THE FISHMEAL PROCESS Åge Oterhals, Ola Flesland and Øistein Høstmark SSF (Norwegian Herring Oil and Meal Industry Research Institute), Kjerreidviken 16, N-5141 Fyllingsdalen, Norway, E-mail: aage.Oterhals@ssf.no Keywords: fishmeal, proteolytic enzyme activity, protease inhibitor, energy consumption ABSTRACT During the summer season severe autolysis may occur in fish raw material used for the production of fishmeal and fishoil due to high proteolytic activity in the gut. The proteolytic activity may result in substantial solubilisation of the fish. During processing a high ratio of the dry matter will follow the stickwater phase and reduce the potential for water removal in the evaporator due to a higher viscosity increase related to dry matter during concentration. Combined with a reduction in the part of total dry matter in the press cake and decanter centrifuge solids, this change in mass balance results in increased energy consumption. The effect of added protease inhibitor (0.4%) in inhibiting the proteolytic activity in summer capelin was studied. The protease inhibitor was added to the fish raw material during unloading of the fish from the boat. Addition of the protease inhibitor product had a clear and positive effect on the mass balance and energy consumption in the process. The reduction in specific energy consumption was estimated to 0.035-0.078 kWh/kg water, depending on the type of evaporator and drying equipment used. This corresponds to only 25-55% of the increased cost. Based on the observed process effects, the addition of the tested protease inhibitor product was not economical.

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