Water sorption isotherms of freeze dried fish sardines

Water sorption isotherms of freeze dried fish sardines were determined at 25, 40 and 50 degreesC using an isopiestic method. Water sorption modeling was carried out using the five-parameter Guggenheim-Anderson-deBoer (GAB) equation. The GAB equation was able to predict equilibrium moisture content (EMC) with a mean relative error of 7.4%. The correlation coefficient (R-2) of the relationship between the actual and predicted values of EMC was 0.986. Modeling with CAB equation predicted monolayer moisture content (X-m) of 4.94% (d.b.). Net isosteric heat of sorption, determined using Clausius-Clapeyron equation, varied from 12.07 to 0.86kJ/mol as moisture content changed from 2.76 to 37.5% dry basis (d.b). Chemical composition analysis showed that fish sardine contained 71% (d.b.) crude protein, 10% (d.b.) fat and 15% (d.b.) ash.