The effects of brine concentrations on the drying characteristics and microbial quality of dried fillets of African Catfish (Clarias gariepenus)

Abstract

This study evaluates the drying characteristics of brined fillets of African catfish (Clarias gariepenus) at four brine concentrations (0, 10, 15 and 20%) and four drying temperatures (40, 50 60 and 70o C). Fresh catfish samples were obtained from a farm at Ikorodu, Lagos. They were cleaned, gutted and cut into fillets of approximately 5×4×3 cm sizes and soaked in the different concentrations of salt (NaCl) solutions for about 6 hours. Thereafter, the fillets were placed on trays and dried in a cabinet dryer till no appreciable changes in weight of the samples were observed. The drying data obtained were analyzed and employed to construct the drying curves, obtain the drying rate constants, the diffusion coefficients and activation energy. Drying rate increased with drying temperatures, with the fillets experiencing greater moisture loss at the initial stage of drying. Fillets dried at temperatures higher than 60 oC acquired the aroma of cooked fish. Both the drying rate constants and diffusion coefficients increased with increasing temperature. Microbial analysis revealed that the higher the salt concentration, the lower the microbial load on each of the dried samples at the different drying temperatures. The microbial load -population of total viable count recorded in this study varied from 4.50 × 105 cfu/g (70oC, 20% salt concentration) to 3.08 × 107 cfu /g (40oC, 0% salt concentration). Thus, drying temperature and salt concentration has profound effects on the drying rates as well as the microbial load of the dried catfish.