Influence of osmotic pre-treatments on rehydration characteristics of carrots

Abstract

The effect of water (0 °Brix), as well as osmotic pre-treatment (5–60 °B), on the rehydration kinetics of carrot slices has been investigated, and compared with control samples. The diffusion coefficient for water infusion and solute loss during rehydration of osmotically pre-treated and finally dried samples were estimated considering unsteady state mass transfer during rehydration. The result shows that treatment up to 10 °B resulted in an increase in moisture diffusion and decrease in solid diffusion. It may be due to the lower concentration of sucrose, which imparts structure and mechanical strength to the tissue, as well as maintaining the general protein (present in plant cells membrane) structure in the dry state and hence, the protecting membrane shows its functionality upon rehydration. Maximum water diffusion and lowest solids diffusion was observed for samples treated with water (0 °B). The samples pre-treated with more than 20 °B could not absorb as much water, in comparison with the control, because of cell permeabilization, due to osmotic stress. At the same time, solute loss during rehydration increased, possibly due to structural changes induced by osmotic pre-treatment, and interaction of the osmoactive substance with the cell component.