Appropriate coating pretreatment enhancing osmotic dehydration efficiency of scallop adductors

Abstract: During osmotic dehydration, extensive solute uptake induces undesirable side effects (such as counteracts water removal, modifies nutritional and/or organoleptic properties in a negative mode, damages the product profile, etc.). In order to explore a novel approach to monitoring solute uptake during osmotic dehydration, effect of 3 coating pretreatments (viz., chitosan, low methoxyl pectinate and sodium alginate) on mass transfer process during osmotic dehydration of scallop adductors was investigated. Peleg's equation was employed to model the mass diffusion and its kinetics. Crank's analytical solution to Fick's second law was also adopted to evaluate the diffusivity of water (Dew), solute (Des) and osmotic dehydration efficiency (Dew/Des). Osmotic dehydration process was significantly (P<0.05) influenced by the type of coating materials, temperatures and salt concentrations. Generally, the initial rates of water loss and salt uptake, and the amounts of water loss and salt uptake at equilibrium in coated samples were lower than that in non-coated ones. Effective diffusivity coefficients increased with increasing temperature and were found to be ranged from 1.224?10-9 m2/s to 2.321?10-9 m2/s, and 1.152?10-9 m2/s to 1.894?10-9 m2/s for water and salt, respectively. Coating treatments prior to osmotic dehydration could effectively monitor the solute uptake at high temperatures, while maintaining the amount of water loss. Coating with sodium alginate and low methoxyl pectinate prior to osmotic dehydration led to higher (P<0.05) osmotic dehydration efficiency Dew/Des than that of non-coated ones. However, coating with chitosan resulted in higher (P<0.05) osmotic dehydration efficiency Dew/Des than non-coated ones as salt concentration of 30% irrespective of temperature or 20% with temperature of 35 ℃. Coating is promising in monitoring solute uptake and promoting dehydration efficiency during osmotic dehydration of scallop adductors.