Abstract:Infrared drying experiments were carried out under different drying conditions. The apparent density, porosity, volume ratio variation and volume shrinkage of the dehydrated samples were researched. The experimental results showed that changes of apparent density were proportional to sample thickness in the initial drying process, and the apparent density was inversely proportional to radiation distance and radiation power. The final apparent density of dehydrated carrot was between 1.01×103~1.71×103kg/m3. The apparent density of fresh carrot slices was 1.05×103kg/m3. With the decrease of water content, the apparent density increased, and the maximum value was 1.71×103kg/m3. The porosity increased with the decrease of moisture content. Sample thickness was proportional to porosity inversely, and the radiation distance was proportional to porosity, but when the radiation power exceeded a certain range the porosity would decrease. In the whole drying process, the range of the carrot’s porosity was between 0.24 and 0.62. The sample thickness and radiation power had a significant effect on volume ratio variation and volume shrinkage. The two order polynomial was fitted with the test data by the linear least square method, and the exponential equation was fitted by the nonlinear least square method based on Matlab 7.0. The maximum determination coefficient R2 of two order polynomial was 0.9966, the minimum value was 0.9762. But the maximum determination coefficient R2 of exponential equation was 0.9601，the minimum value was 0.9017. The fitting results showed that two order polynomial model was a good fit to predict the relationship between shrinkage and the dry basis ratio of carrot more accurately.
