Characterization of the fuji apple drying in thin layer: determination of glucose content, color and production

Abstract

The aim of this work was to study the convective drying of Fuji apple (Mallus percicae) in thin layer and to evaluate the characteristics of the dried product. The air flow was perpendicular through the samples with air velocity of 1.5 m s-1. The study factors were the air temperature (60, 70 and 80ºC), sample thickness (3,4 and 5 mm) and citric acid solution concentration (0, 0.5 and 1 %). The glucose content and the samples color were found through spectrophotometer method. Five empirical models were used to evaluate the experimental data of the drying process. The fit of the drying data for the estimate of drying constant (K) showed high values of correlation for all models (R2 > 0.99). The Henderson-Pabis model was chosen for determination of the moisture average effective diffusivity (Deff). Through the surface response methodology, it was found that the samples with higher production and better physical-chemical characteristics was in conditions of air temperature at 70ºC, sample thickness of 3 mm and citric acid solution concentration of 1%.