Authors

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.

Abstract in Chinese

甘薯是一种日常食用的重要根茎类作物。为了降低损坏、提高品质和延长储藏期，需对甘薯进行有效的加工处理。近红外干燥具有干燥速率快、均匀性好和效率高等优点。本文开发了一套实验用近红外干燥机用于甘薯片的干燥性能和工艺优化研究。依次对甘薯片进行近红外干燥的单因素试验、正交试验和变温试验。以温度、甘薯片厚度和蒸制时间为控制因子，有效水分扩散系数、总色差、比能耗和干燥时间为评价指标。对各评价指标赋予均等权重后得到综合指标。实验结果和数据分析表明：70 ºC (75min) - 65 ºC (至结束)的降温模式变温干燥工艺具有最佳干燥性能；常温干燥工艺的最优控制因子参数组合为：甘薯片厚度3mm、温度70 ºC、蒸制时间6min；Midilli模型对水分比的实验数据具有最佳拟合近似度，其决定系数0.99933、卡方0.00007、平均根方误差0.00838；高的温度（75 ºC）和大的甘薯片厚度（9mm）不适合用于甘薯片的近红外干燥。本文研究结果可为基于甘薯片近红外干燥工艺和干燥机设计提供参考。