Isothermal and differential scanning calorimetries to evaluate structural and metabolic alterations of osmo-dehydrated kiwifruit as a function of ripening stage

Water state and sugars in cranberry fruits subjected to combined treatments: Cutting, blanching and sonication

To ease the mass exchange in fruit tissues, cutting and blanching are traditionally performed. However, recently, unconventional methods such as sonication are becoming more popular, which cause several alterations of physical and chemical properties as well as microstructure changes. The aim of this work was to evaluate the distribution of water inside the cranberry fruits, microstructural changes and sugars content, following traditional and sonication pre-treatments in osmotic solutions. TD-NMR spectroscopy was used to measure the transverse relaxation time (T₂) and intensity of proton pools in different cellular compartments. The microstructure of the samples was evaluated by SEM microscopy, sugars content by HPLC and sucrose melting temperature and enthalpy by DSC. Different pre-treatments appeared to promote microstructure alterations and loss of water from vacuole and cytoplasm/extracellular space, more pronounced in cut and blanched samples. Cutting and blanching followed by osmotic dehydration with assisted sonication eased sucrose penetration into the tissue.

Description of Osmotic Dehydration of Melon Cubes using a Three-dimensional Diffusion Model: An Algorithm to Determine the Effective Diffusivity

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.

Guava Osmotic Dehydration: Description by Two-Dimensional Diffusion Models Considering Shrinkage and Variations in Process Parameters

This article describes the osmotic dehydration of guava dipped in sucrose solutions using two-dimensional numerical solutions of the diffusion equation with boundary condition of the first kind. Two models are used: model 1 disregards the shrinkage of the product and assumes that effective mass diffusivity does not vary during the process; model 2 takes into account shrinkage, considering effective mass diffusivity as variable. Process parameters estimation is obtained by means of an optimizer. Comparative analyzes indicate that the proposed models have similar statistical indicators. However, model 2 is recommended, for it presents much higher physical fitness when describing mass migrations. Comparison between two-dimensional numerical models presented in this research and one-dimensional models found in the literature reveals that one-dimensional models overestimate process parameters. In addition, one-dimensional models present limitations in predicting the distributions of water and sucrose on guava slices.