Quality comparison of mulberry powder by hot air drying and vacuum freeze drying

The quality of two kinds mulberry powders produced by hot air drying and vacuum freeze drying were compared. The results illuminated that both yield and moisture content by vacuum freeze drying were lower than hot air drying,but vacuum drying showed a better solubility. The images taken by the scanning electronic microscope showed the particles of vacuum freeze drying powder were more porous and larger in comparison with the hot air drying. The retention ratio of Vc,total phenol,and anthocyanin of vacuum freeze drying powder was 97. 97%, 98. 40%,96. 36% respectively,while hot air drying powder was much lower at 37. 47%,92. 07%,69. 13%,respectively. Therefore,vacuum freeze drying is better in maintaining the quality of mulberry powder.