Effect of Combined Infrared and Hot-Air Drying on the Chemical and Color Characteristics of Sweet Potato Slices

Utilization combined infrared and hot-air drying strategies for sweet potato with and without pretreatment under different levels of air-drying temperature, infrared radiation and thickness and its impact on chemical and color attribute. Evaluation tests showed that total soluble sugar and total carbohydrate content increased with the increase of air-drying temperature and infrared radiation. While it decreased with the thickness of the slices increasing. The high values for all soluble sugar and carbohydrate were 0.802 and 0.452 mg/ml (in untreated) and 0.833 and 0.512 mg/ml (in treated) under the condition of the highest temperature and infrared radiation level and less thickness. β-carotene was decreased with the increase of temperature, slices thickness and infrared radiation intensity, The high value of β-carotene were 0.49 and 0.64 mg/100 g, respectively (for untreated and treated slices) at the lowest temperature, infrared radiation level and thickness. For color, the maximum lightness (L*), redness (a*) and hue angle (H°) were 74.62,15.7 and 88.53 for treated sweet potato slices while the maximum yellowness (b*), chrome (C) and Browning Index (BI) were 55.46, 55.53 and 208.29 for untreated sweet