Study of drying characteristics of Indian mackerel (Rastrelliger kanagurta) in CIFT solar-electrical hybrid dryer

Abstract

Fresh Indian mackerel was thoroughly washed, eviscerated, cut into butterfly style and salted overnight with dry salt . The salted mackerel was dried in a solar electrical hybrid dryer at the air temperatures of 45–55 degree celsius, relative humidity of 66–80 per cent, and air flow rate of 0.60–0.80 meter per second. The solar radiation ranged between 86 and 750 W per square meters during the time of experimentation. To maintain the optimum drying temperature, supplemental heating was provided by two electrical coils of 1500 W each in addition to the solar heat energy. The initial moisture content of the salted mackerel was 61.5 per cent and reduced to the final moisture content of 31.8 per cent during drying. Drying curves like Moisture content vs Time, Drying rate vs Time and Moisture ratio vs Time were plotted. The moisture content was gradually decreased with drying time and taken 8hrs for complete drying. The entire drying process was observed to be occurring under falling rate drying period. The dried mackerel fish was evaluated for various quality parameters and observed to be within the acceptable limit. Various drying models were applied and the coefficients of determination and constants were evaluated by nonlinear regression to estimate the drying curves of dried mackerels.