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\xa0°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\xa0°C with a constant air velocity of 1\xa0m/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 (D eff ) of the by-product drying were ranging from 8.87\u2009×\u200910 −10 to 1.47\u2009×\u200910 −9 \xa0m 2 /s and increasing drying air temperature led to an increment of D eff . Rehydration properties including weight gain (%), rehydration ratio and co-efficient of reconstitution of dried sample at 60 and 70\xa0°C were higher than the drying at 50\xa0°C. Peleg model was the best fit with rehydration data. The D eff of moisture absorption was in the range from 6.49\u2009×\u200910 −9 to 7.31\u2009×\u200910 −9 \xa0m 2 /s.