Effect of Pulsed Electric Field on Collapse Phenomenon of Apple Tissue in Vacuum Freeze Drying

Abstract

The effects of pulsed electric field (PEF) on drying characteristics and collapse phenomenon during vacuum freeze drying of apple were investigated. The effects of PEF treatment on drying time, specific energy consumption and rehydration ratio were studied separately with different temperature. Results showed that the board temperature should below the collapse temperature of apple to increase the drying rate without destroying the quality during sublimation processing, and the collapse temperature of the apple after PEF treatment was 75°C, the board temperature should be as high as possible at the maximum allowable temperature of 85-95°C during the desorption processing according to the drying experiment and microstructure analysis. Moreover, the influence mechanism of PEF treatment on collapse phenomenon was discussed from the perspective of moisture migration and mechanics. Therefore, PEF treatment can improve the diffusion rate, and increase the collapse temperature.