Drying characteristics and quality of Chinese yam by multiphase microwave drying based on fractal theory

Abstract

A multiphase microwave drying (MMD) was proposed to produce dried Chinese yam cubes with good quality comparable to freeze-dried products. The effects of different microwave power loading schemes on the conversion point (water phase in samples changes from solid-to-gas to liquid-to-gas) of MMD were assessed, and the macroscopic physical properties and microstructure characteristics of dried yams were investigated. Results showed that with an increase of microwave power, the time required to reach the conversion point was reduced. And the moisture content at the conversion point as affected by microwave power loading schemes had vital influence on sample quality. When it was 0.378 g·g−1, the properties of the yam cubes resembled those of freeze-dried samples in terms of rehydration, texture, and microstructure. Furthermore, a fractal theory-based microstructure characterization can accurately reflect texture characteristics. MMD has the potential to produce high quality products that matched to freeze-dried ones.