Studies on combined hot-air and microwave vacuum drying of Lithi pulp

Orthogonal test was carried out to investigate the effects of hot air temperature, conversed moisture content, microwave intensity and pulse ratio on the L value of the dried litchi pulp, specific energy consumption and sensory score respectively. The results showed that the optimum conditions for drying of litchi pulp by hot air and vacuum microwave combination were found to be hot air temperature 80°C conversed moisture content 50%, microwave intensity 20 W/g and pulsed ratio (10s∶40s). The optimized combination drying process reduced specific energy consumption by approximately 50% as compared with conventional hot air drying, and under such conditions, the quality of dried litchi pulp was better than hot air drying or microwave vacuum drying.