This paper aims to study the transient mass diffusion during the osmotic dehydration of melon cubes, using the analytical solution of the diffusion equation with boundary condition of the first kind. Two techniques are used to determine the effective mass diffusivity, using experimental data. In technique 1, available in the literature, the domain of the effective diffusivity is scanned from a value close to zero, until the minimum value of the objective function (Chi-square) is determined. Technique 2, proposed in this paper, uses an algorithm based on the optimal removal of experimental points, until obtaining the objective function with a minimum value, allowing to determine the optimal value for the effective mass diffusivity. The obtained values for diffusivity and statistical indicators revealed that both techniques generate equivalent results and allowed to satisfactorily describe the kinetics of osmotic dehydration of melon cubes. However, technique 2, proposed in this paper, is much faster than technique 1, in the determination of effective mass diffusivity, for all analyzed sets of experimental data.

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This study aims to perform the thermal analysis of Japanese rice starch submitted to different milling processes (balls, discs and knives). Starch was extracted with sodium metabisulphite solution (0.2%), crushed, decanted and dried at (50 °C) to constant weight. The thermal properties were analyzed by thermogravimetry and differential exploratory calorimetry techniques. It can be argued that the granules of the Japanese rice native starch are poorly resistant and knife milling made them more susceptible to breakage with prolonged heating. The different milling techniques significantly modified the thermal properties of the Japanese rice starch, since in the thermogravimetry analysis the formulation obtained through the disc mill presented distinction in relation to the mass loss, while for the differential exploratory calorimetry the starch obtained in the process. The milling process with the ball mill presented lower initial gelatinization temperature and higher gelatinization enthalpy.