Experimental study of hot air dehydration of Sultana grapes

Diffusion models for the description of seedless grape drying using analytical and numerical solutions

“…By substitution of Eq.9 into Eq.7, with n = 1, a transcendental equation is obtained, and the root 1  , corresponding to n = 1, can be determined. Thus, the Biot number is also determined through Eq.9, and the effective mass diffusivity by Eq.12.…”

“…In the second case, the life time of the product is much higher than in the first case, beyond resulting in a food very appreciated in several parts of the world: raisins. The drying process of grapes under natural conditions [1] is generally slow due to the resistance of its skin. In order to increase the drying rate, commonly a pretreatment is accomplished before drying.…”

“…Several drying models are available in the literature: empirical models [1][2][3][4][5], and diffusion models, which are very common to describe drying kinetics of grapes [1,3,[4][5][6][7][8][9]. In order to describe the drying kinetics through a diffusion model, the initial and boundary conditions must be known.…”

“…In order to describe the drying kinetics through a diffusion model, the initial and boundary conditions must be known. In general, the appropriate boundary condition is of the third kind [6,7,9], but the first kind one is also found in several research works [1,[3][4][5][6]8], especially if some pretreatment is used before the drying process. For some products, like rice, drying does not substantially reduce the volume of the product and the shrinkage can be discarded [10,11].…”

“…Some research works present analytical solutions for the diffusion equation, particularly if the boundary condition is of the first kind [1,[3][4][5][6][7]. If an analytical solution is proposed for the boundary condition of the third kind, the series which represents the solution is normally expressed by only the first term, and the process parameters are determined by regression [13,14].…”