Evaluation of desorption isotherms, drying characteristics and rehydration properties of crab stick by-product

Abstract

Crab stick by-product is the underspecification product from crab stick production. The by-product contains high moisture content inducing a short shelf life. Therefore, drying is considered as a food preservation technique to extend its shelf life. This study is focused on an investigation of desorption isotherms, drying characteristics and rehydration properties of crab stick by-product. Desorption isotherms were determined at three different temperatures (20, 35 and 50 °C). The experimental data obtained were modeled by fourteen sorption isotherm models for water activity ranging from 0.36 to 0.99 and Double Log Polynomial model was found to be the best-describing model. The net isosteric heat of desorption increased continuously with decreasing of equilibrium moisture content. The crab stick by-products were dried at 50, 60 and 70 °C with a constant air velocity of 1 m/s. The drying data were fitted with five thin layer drying models and Approximation of diffusion model was the best-describing model. Drying curves showed only falling rate period. Moisture diffusivities (Deff) of the by-product drying were ranging from 8.87 × 10−10 to 1.47 × 10−9 m2/s and increasing drying air temperature led to an increment of Deff. Rehydration properties including weight gain (%), rehydration ratio and co-efficient of reconstitution of dried sample at 60 and 70 °C were higher than the drying at 50 °C. Peleg model was the best fit with rehydration data. The Deff of moisture absorption was in the range from 6.49 × 10−9 to 7.31 × 10−9 m2/s.