The effect of blanching and freeze-thaw pretreatment on the drying rate of carrots and the relationship
between drying rate and state of cell membranes, cell wall and pectin methyl esterase (PME) activity in
the pretreated tissues were investigated. Frozen-thawed samples showed the highest drying rate and
samples blanched at higher temperature showed a higher drying rate. Samples blanched at 60 C showed
a lower drying rate than fresh samples. Electrical impedance analysis and microscopic observation
suggested that cell membrane injury and changes in pectin structure in the cell walls due to the pretreatments
greatly affected the permeability and drying rate of the samples. Also, the significantly high
drying rate of frozen-thawed samples was attributed to the formation of ice crystals that facilitated water
migration. The samples blanched at 60 C showed the highest residual pectin methyl esterase activity, suggesting that the
decrease in drying rate for these samples was attributable to the inhibition of water migration due to the
cross-linked structure of pectins formed by pectin methyl esterase activity.