ABSTRACT
Objective: In order to explore suitable drying technology for yam slices, the effects of three different drying methods, namely medium and short infrared wave drying, air impingement drying, pulsed vacuum drying, on drying kinetics and quality attributes of yam slices were investigated. Methods: The moisture ratio, drying rate curves along with the change of drying time and relationship between dry basis moisture content and drying rate of yam slices were studied under three drying methods. Additionally, the effects of the three drying technologies on color parameters (L*, a*, b*), rehydration ratio, allantoin and extract contents were investigated. Results: All drying process of the three drying methods for yam slices belonged to the falling rate period without constant drying stage, and the shortest drying time was only 120 min obtained under air impingement drying temperature of 70 ℃, air velocity of 15 m/s. The effective moisture diffusivities were 7.52 × 10-10, 1.19 × 10-9 and 1.30 × 10-9 m2/s for pulsed vacuum drying, medium and short infrared wave drying and air impingement drying, respectively. The three drying methods were comprehensively evaluated based on seven indexes including rehydration ratio, drying time, extract and allantoin content, etc. The comprehensive scores of medium and short infrared wave drying, pulsed vacuum drying and air impingement drying were 0.29, 0.59, and 0.70, respectively, which indicated that air impingement drying obtained the highest score. Conclusion: Comprehensive evaluation results showed that the best drying method for yam slices drying is air impingement drying and the air impingement. This study provides a theoretical basis for the exploration of suitable drying technology and drying conditions for yam slices dehydration.