Abstract:

Response surface methodology (RSM) was employed to optimize the conditions for vacuum freeze drying of
apples slices. The thickness of apple slices, heating plate temperature and working pressure were considered to be the most
important factors affecting the freeze-drying of apple slices as well as quality characteristics of final products (crispness,
color, moisture). A regression model indicating each of the quality characteristics with respect to the important factors
was developed based on a Box-Behnken design. By employing response surface methodology, we established the optimal
conditions for vacuum drying apple slices as follows: 8.31 mm thick apple slices, 71.62 ℃ of heating plate temperature and
62.76 Pa of working pressure. There was a good agreement between the experimental and predicted quality characteristics
under these conditions.

Key words: apple, vacuum freeze drying, response surface methodology