A STUDY ON RE-STRUCTURED SNACKS MIXED LYCHEE( Litchi chinensis Sonn.) WITH PURPLE SWEET POTATO( Ipomoea batatas batatas.) DRIED BY VACUUM MICROWAVE DRYING

摘要

High sugar content of lychee limits the production of dried lychee snacks.Purple sweet potato was blended with lychee to develop new snacks dried by vacuum microwave drying (VMD) in this research.Increasing 4.8% sugar content significantly improved the dielectric loss value of materials and drying rate when water content was above 50%.However, the effect can be neglected when water content was below 30%. The optimal proportion of materials and drying conditions were determined in terms of sensory evaluation, crispness and quality. The desirable ratio of lychee to purple sweet potato was determined to be 3: 7.Adding gelatinized potato starch in mixed slurry can increase the crispness of chips. The optimal adding content was 4%.Moreover, 2 W/g was the optimal microwave power density.Last, pictures taken by thermal infrared imager clearly show the temperature changes and temperature distribution at various stages during VMD.