Effects of far-infrared radiation temperature on drying characteristics, water status, microstructure and quality of kiwifruit slices

Far-infrared radiation (FIR) drying is an advanced technique that has recently been applied in food processing. In order to reveal the effects of FIR temperature on dehydration process and quality characteristics of kiwifruit slices, FIR drying experiments on kiwifruit slices were conducted. Low-field nuclear magnetic resonance, scanning electron microscopy, colorimeter and chemical analysis were applied to explore the dynamic water states, microstructure, color changes and nutritional components of kiwifruit slices at different FIR temperatures. The results showed that drying time reduced by 57.9% and average drying rate increased by 137.5% as FIR temperature increased from 120 to 280 degrees C. The water mobility and distribution in kiwifruits changed with the extension of drying time, and increasing FIR temperature could accelerate the migration and removal of moisture. Higher FIR temperature could produce more cavities and larger channels in dried samples. An increase in FIR temperature decreased L* but increased a* values of dried kiwifruits and affected total phenolic content, total flavonoids content and Vitamin C content. Therefore, FIR drying is a promising method to improve drying rate as well as protect product quality of kiwifruit slices.