Changes in biochemical and microbiological quality of silverside during two drying process were investigated. Total fatty acid and amino acid contents in silverside were 5.42 and 10.9 g 100 g )1 fresh sample, respectively, in which, palmitic acid and glutamic acid were the most abundant. N-3 and n-6 polyunsaturated fatty acids (PUFA) levels were 0.59 and 0.62 g 100 g )1 fresh silverside respectively. After hot air and solar drying treatments, Peroxide value and thiobarbituric acid reactive substances of the total lipids increased significantly (P < 0.05) to reach 2.58 and 3.41 meq active O 2 kg )1 oil and 0.87 and 1.27 mg MA kg )1 oil, respectively. Fatty acid profile of non-polar lipid remains unchanged during experimental drying process. However, PUFA (% of total fatty acids) of polar lipid decreased significantly (P < 0.05) during both drying process with lower levels in solar drying process. Drying conditions had a significant effect on the microbiological quality. Therefore, mesophiles and total coliforms increased within drying treatment with higher counts in solar drying process.

The aim of this work was to study the effect of air‐drying process on the convective drying kinetics of silverside fish and to determine the suitable thin‐layer drying model. This product is chosen for its high‐protein content and nutritional value, and its use as a very important foodstuff in developing countries. A nonlinear regression procedure was used to fit experimental drying curves with most used empirical mathematical models available in literature. The comparison criteria between experimental and calculated data were the coefficient of determination and the reduced χ2. It was found that the Midilli et al. and two‐term models give the best fit. The effective diffusivity was determined to be 8.7630 × 10−10–3.2131 × 10−09 m2/s in the temperature range of 45–70C and in the relative humidity range of 20–40%. The activation energies for moisture diffusion were calculated to be varied from 35.6471 to 37.2625 kJ/mol. PRACTICAL APPLICATIONS Fish is a major source of food for human nutrition. In fact, silverside fish are certainly a source of proteins and lipids, approximately 6.09 and 19.11 g/100 g, respectively. Therefore, silverside has a great importance in Tunisian food customs. This product is characterized by its high contents of moisture, which represent the most significant cause of their deterioration after its fishing, particularly in relatively hot countries. Fish can thus be valorized by drying, which is an efficient technique for improving stabilization and storage. Thus, the basic objective in drying agricultural products is the removal of water in the solids up to a certain level, at which microbial spoilage and deterioration chemical reactions are greatly minimized. Moreover, knowledge of drying behavior is important in the design, simulation and optimization of the drying process.

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The aim of this work was to report drying characteristics and sorption isotherms of silverside fish. The sorption isotherm was determined at four temperature levels 40, 50, 60 and 70°C and at water activities, ranging from 0.058 to 0.89, using the static gravimetric method. Five sorption models were fitted with the desorption data generated from the gravimetric method. It was found that the Peleg model suitably represents the sorption experimental data in the mentioned investigated ranges of temperature and water activities. Sorption isosteric heat was determined from sorption data using the Clausius-Clapeyron equation. The relationship between the net isosteric heat of sorption and the moisture content was best expressed by the Tsami's equation. The drying characteristic curve and the drying rate expression of silverside fish have been established from experimental convective drying kinetics.