Experimental study on technological parameters of freeze-drying of mushroom

The purpose of this paper is to determine the most efficient freeze-drying technological parameters of mushroom in order to improve its efficiency and quality. The relationship between the drying time, ratio of volume shrinkage, ratio of water absorption, as well as the drying pressure of drying chamber, temperature of the board, the velocity of decreasing temperature during the process of freezing, the material thickness through the two orthogonal experiments with four factors and five levels and single factor experiment, and the mathematical models were established to describe the parameters. At last the optimal combination of the parameters for the freeze-drying technology of mushroom was obtained through optimized theory in many targets and in nonlinear method. They are as follows: under ensuring quality, the drying pressure of drying chamber is 111 Pa, the temperature of the board is 42.5℃, the velocity of decreasing temperature during freezing is -0.29℃/min, and material thickness is 6～10 mm.