Abstract:

Freeze drying of banana slices can offer high quality banana products. The diffusion coefficient of water vapor
in the dry area influenced the setting of the shelf temperature or the radiant plate temperature, which was one of the key
factors affecting the lyophilization process. According to the weight changes of banana slices during freeze drying, the
effective diffusion coefficient of water vapor in the dried zone was obtained. The impacts of maturity degree, precooling
velocity and color fixative on the value of diffusion coefficient were examined. Results showed that the effective diffusion
coefficient of water vapor ranged between 1.0 × 10-4 m2/s and 3.5 × 10-4 m2/s. The impact of precooling velocity was
the largest while maturity degree had the least effect. Addition of color fixative caused a slight reduction of the diffusion
coefficient.

Key words: banana slices, freeze drying, water vapor, diffusion coefficient