Foam-mat convective drying of kiwiberry (Actinidia arguta) pulp

Abstract

The purpose of this work has been to determine the optimal conditions for the processing of kiwiberry fruit pulp based on the relevant thickness of the layer and air temperature, that will target the maximal reduction of drying time and minimal energy consumption. The research was designed to use the response surface methodology (RSM). The effects of independent variables (factors) such as the thickness of the layer (4, 8, and 12 mm) and the temperature of the drying air (50, 60, and 70°C) were studied by the means of the response variables. In this study, the drying kinetics was evaluated based on the drying time, drying rate, and effective water diffusion coefficient (D<sub>eff</sub>). Based on the simplified Fick's second law of diffusion, D<sub>eff</sub> was determined, while the relative water content [moisture ratio (MR)] was predicted using empirical models. It was found that as the temperature of the drying process increased, the process time was reduced, and the drying process intensified, which was manifested by the increment of the drying rate as well as the effective moisture diffusivity (varied from 5.58 × 10<sup>–10</sup> m<sup>2</sup> s<sup>–1</sup> to 27.2 × 10<sup>–10</sup> m<sup>2</sup> s<sup>–1</sup>). The mathematical model, developed using the RSM, showed a good fit for the data obtained in the study, which allowed to predict the response of the effective water D<sub>eff</sub> of the foamed kiwiberry fruit pulp with R<sup>2</sup> > 0.97.