Combined effect of gamma-irradiation and osmotic treatment on mass transfer during rehydration of carrots

The exposure to irradiation pretreatment results in increase in cell wall permeabilization, leading to softening of tissue and the loss of turgor pressure, thereby affecting the reconstitution properties. Rehydration kinetics of gamma-irradiated (3.0–9.0 kGy) and water (0° Brix) or osmotic pretreated (up to 50° Brix) carrot samples were studied. The diffusion coefficient for water infusion and solute loss during rehydration of irradiated and osmotically pretreated and finally dried samples were estimated considering Fickian diffusion. The results shows that as increase in doses of gamma irradiation resulted in decrease in water and increase in solute diffusion coefficient. The pretreatment with water (0° Brix) resulted in increased water gain and reduced solute loss during rehydration for irradiated samples. The samples pretreated with osmotic solution of 10° Brix (concentration more than the natural cell water concentration) could not absorb more water in comparison with control because of cell permeabilization caused by the osmotic treatment due to osmotic stress. The water diffusion coefficient values decreased and solute diffusion coefficient increased with an increase in dose rates. The equilibrium moisture as well as equilibrium solid content were dependent on the treatment conditions.