Optimization and Characteristic Analysis of Apple Hot-air Drying Process

In order to improve the quality of apple slices during hot-air drying process,ultrasound and color fixative(0.1% NaCl,1.0% sucrose and 0.8% trehalose)were used as pretreatments. Temperature of hot air,thickness of slices and pretreatment were used as experimental factors to orthogonally study the hot-air drying process of apple slices and mathematical model of hot-air drying characteristics of apple slices was established. The results showed that the drying rate increased with the reduction of the slice thickness and the increase of the hot air temperature. Both the ultrasound and the color fixative promoted the drying process. The best hot-air drying process parameters for apple slices were hot air temperature of 60 ℃,thickness of 1.5 mm,and pretreatment method as color fixative.Weibull model was the best model to simulate the hot-air drying characteristics of apple slices. The effective diffusion coefficient of apple slices was among 1.1278×10^-8~5.2940×10^-8 m²·s^-1. The results provided a reference for the actual hot air drying of apple.