Effects of different drying methods on the quality of Ziziphus Jujube Mill.cv.Hupingzao

The hot air drying( HD),vacuum drying( VD),vacuum freeze drying( FD),two- fluid spray drying( TFSD)and ultrasonic spray drying( USD) technologies were used to dry Ziziphus Jujube Mill.cv.Hupingzao in this paper.And the properties( moisture content,color difference( ΔE),water- soluble component,particle size distribution) of the dried product by the five drying methods were compared.The HD and VD demonstrated significant impact on the water- soluble component of the product,and the ΔE of the products were higher. The product by TFSD and USD were more granular,the moisture contents of that were lower( 2.39% and 2.58%),and the particle size distribution of that appeared normal distribution within 30 ~ 200 μm and the average value was 75 μm,but the products by HD,VD and FD were showed in block shape. Considering all these factors,TFSD and USD were the suitable drying methods for jujube drying.