PERFORMANCE ANALYSIS AND TECHNOLOGY OPTIMIZATION OF INFRARED DRYING OF SWEET POTATO SLICE

Abstract

Sweet potato (Ipomoea batatas L.) is an important tuber crop for the daily consumption. Efficient processing must be taken to reduce wastage, and to improve quality and extend shelf period of sweet potato products. Infrared (IR) drying has advantages of high drying rate, good uniformity, and high production efficiency. A laboratory infrared (IR) dryer was developed to study the drying performance of sweet potato slice and its technology optimization in this paper. Single-factor, orthogonal, and temperature-varying experiments of IR drying of sweet potato slice were conducted sequentially. Temperature, slice thickness and steaming time were defined as control factors, and effective moisture diffusivity (EMD), total color change (TCC), specific energy consumption (SEC) and drying time were defined as evaluation indexes. Same weights were applied to the synthetic evaluation index (SEI). Experiment results and statistical analysis showed that: temperature-varying IR drying technology of temperature-decrease mode, under drying conditions of 70ºC (75min) - 65ºC (to end), showed the best drying performance; the optimal combinations for temperature-constant were slice thickness 3 mm, temperature 70ºC, and steaming time 6 min; Midilli et al. model gave the best approximation to experimental data of moisture ratio, with coefficient of determination 0.99933, reduced Chi-square 0.00007, and root mean square error (RMSE) 0.00838; high temperature (75ºC) and large slice thickness (9 mm) were not suitable for IR drying of sweet potato slice. The results of this study can provide references for research on IR drying technology and design of IR dryer for sweet potato slice.