Effect of internal porosity on water absorption and volume of dried vegetables during soaking
2009
Orikasa, T.(National Food Research Inst., Tsukuba, Ibaraki (Japan)) | Takagawa, T. | Shiina, T. | Tagawa, A.
Water absorption characteristics of three kinds of dried vegetables (eggplant, radish and carrot) were investigated during soaking. Changes in moisture content of these samples were measured at four temperatures ranging from 20 to 70degC. The infinite plane sheet diffusion model was used to describe the water absorption process for these samples; the measured results agreed well with the calculated results. The diffusion coefficients were 2.8 x 10E-9 to 1.0 x 10E-8 square m/s for eggplant, 1.5 x 10E-9 to 9.1 x 10E-9 square m/s for radish and 1.2 x 10-9 to 8.9 x 10E-9 square m/s for carrot. Using an Arrhenius-type equation the relationship between the diffusion coefficients and temperature was determined to estimate the activation energy for each sample. In addition, changes in volume during soaking were determined by measuring the apparent density, true density, and specific volume on a dry basis for the dried vegetable samples at various moisture contents. From the apparent density and true density, internal porosity was determined and its effect on water absorption and volume of the three kinds of dried vegetables was evaluated.
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