Equilibrium Moisture Content Isotherms of Codfish (Gadus morhua)

Abstract

Industrial drying of salted fish is an extremely common practice in the Portuguese industry of codfish processing. The present study aims to obtain sorption isotherms of codfish, which will be useful in designing drying processes and prediction of storage conditions for this product. The equilibrium moisture contents (wet basis) were determined for salted codfish at 15, 18, 20, and 23^ºC at relative humidities ranging from 40 to 70%. Experiments were also carried out for fresh codfish at the temperature of 20^ºC for the same values of relative humidity. The sorption capacity of codfish decreased with an increase in temperature at constant relative humidity. Thirteen models were used to correlate the experimental data analysis of salted codfish: modified BET, Cauri, Chung-Pfost, modified Chung-Pfost, GAB, modified GAB, Halsey, modified Henderson, Kuhn, Oswin, modified Oswin, Smith, and modified Smith. Based on the mean relative percentage deviation, standard error of estimate, randomness of residual, and coefficient of determination, experimental data were well described by all the models. The equilibrium moisture content of salted codfish was best predicted using the modified GAB model, with a coefficient of determination of 0.99.

Keywords:

• sorption
• isotherms
• drying kinetics
• salted fish

Acknowledgments

The present work was conducted with the support of the FCT (Foundation for Science and Technology) through a PhD scholarship (Contract number: SFRH/BD/43532/2008).