Assessment of the effect of air humidity and temperature on convective drying of apple with pulsed electric field pretreatment

Abstract

This research aims at assessing the impact of pulsed electric field (PEF) pretreatment and various properties of drying agent (absolute humidity, temperature) on the course of convective drying (CD) of apples. Moreover, the selected quality indicators of obtained dried materials (dry matter content, water activity, hygroscopicity, rehydration, color, total phenolic content, antioxidant activity) have been evaluated. As a result of increased permeabilization of cells, PEF reduced time of CD of apples even by 20%. However, lower total phenolic content and antioxidant activity in PEF-pretreated dried samples were observed. With the use of PEF, the release of phenolic compounds from the cellular structures of the apple tissue could occur, making them more susceptible to thermal degradation. After introducing the dehumidification system, an increase in the drying time of apples was observed. It could be so due to case hardening, which further deteriorated the reconstitution properties of the obtained dried materials.