Chemical Properties and Moisture Sorption Isotherm of Smoke- Dried Catfish (Clarias gariepinus) and Mackerel (Trachurus trachurus) Produced with a Modified Smoking Kiln: Application of Four Models to Sorption on Data

Abstract

The effectiveness of a modified smoking kiln, the smoking quality, and the moisture sorption characteristics of smoked dried catfish and mackerel were all investigated in this study. Smoked dried catfish protein, ash, fat and moisture ranged between 73.37 and 73.80 %, 5.00 and 5.40% 10.30 and 11.05% and 8.05 and 8.12% respectively and for smoked dried mackerel 70.58 and 70.67%, 5.00 and 5.94%, 12.99 and13.15%, and 6.14 and 6.37% respectively, while the moisture sorption isotherm confirmed type III BET isotherm with marked hysteresis.  Smoke dried catfish and mackerel's type III isotherm is as expected given that food items high in protein have been observed to display type III forms. For the Henderson, BET, GAB, and Oswin models, the values of the root means square ranged from 2.6 to 8.7, 4.6 to 9.1, 5.9 to 12.1, and 4.1 to 13.16, respectively. The coefficients of determination for these models ranged from 0.95 to 0.99, 0.93 to 0.96, 0.83 to 0.94, and 0.91 to 0.94. For catfish and mackerel, the isosteric heats of sorption for the adsorption and desorption pathways, respectively, were 4.55 and 1.22 kJ/mol and 4.07 and 1.10 kJ/mol, respectively. With an increase in temperature from 20 to 40 oC, the apparent sorbate surface area fell for catfish from 99.38 to 85.02 m2/g solid and for mackerel from 76.01 to 66.25 m2/g solid. The smoking kiln performed the basic tasks of smoking and drying the fishes very well, with high-quality nutrients.