Pulsed electric field enhanced freeze-drying of apple tissue

Abstract

The influence of pulsed electric field (PEF) on freeze-drying of apple tissue was investigated. The freeze-drying was performed with different parameters of PEF treatment, and PEF treatment on the drying characters, microstructure, rehydration ratio, effective diffusion coefficient and hardness of apple tissue were discussed separately. The results indicated that PEF utilization as a pretreatment of apples enhances the drying process. The drying time was shortened by 17.73% at most, specific energy consumption decreased by 24.74% at most, and the rehydration ratio was improved by 65.22% at most for PEF treatment samples respectively, compared with the untreated samples. The effective diffusion coefficients varied from 2.60 × 10−8 m2/s to 4.20 × 10−8 m2/s for PEF pretreated samples, and was 2.40 × 10−8 m2/s for untreated samples drying at 75°C, the hardness of the untreated apple tissue was about 144.4 N which was decreased to 39.5–115.0 N after PEF treatment.