In the drying of food, diffusivity of moisture in the food varies with time according to the local change of the degree of drying.
However, for the design of drying operation the quantitative relation between the degree of drying and the timw of operation might be correlated experimentally.
In this work, for various dimensions and the shape of the sample, it is realized that, the measurement of local diffusivity constant as a function of moisture content of the sample by Wakabayashi's method enable the calculation of correlation between the degree of drying vs time through certain certain simplifications on the solution of Fick's second law.
Experiments were carried out for the cubic, rectangular, spherical and cylindrical "potato" sample, and the above mentioned approaches were seemed to be successful within the relative error of 10 to 30 %.