Impact of pre-treatment methods on the drying kinetics, product quality, and energy consumption of electrohydrodynamic drying of biological materials

Abstract

Electrohydrodynamic (EHD) drying is an energy-efficient drying method. This novel drying technology operates at room temperature, which makes it particularly suitable for drying biomaterials that contain heat-sensitive compounds. It has a higher drying rate than other low-temperature methods, such as solar and freeze-drying. However, its drying rate is not high enough to compete with other conventional thermal methods, such as hot-air drying. For industrial applications requiring high product throughput, the drying rate of EHD drying should be improved. One way to do this is to combine EHD with pre-treatment method. Therefore, this study evaluated the impact of different pre-treatment methods on drying kinetics, energy consumption, and product quality attributes of apple slices dried using EHD drying. Pulsed electric fields (PEF), ultrasound, and blanching are the studied pre-treatment methods. Results show that only PEF pre-treatment could significantly decrease the EHD drying time by 39%. However, it resulted in a 26% higher browning index than the untreated EHD-dried apples, which is not appealing to consumers. The applied pre-treatment methods did not significantly affect other quality attributes, such as antioxidant activity, total phenolics, and rehydration ratio. In conclusion, using the studied pre-treatments for EHD drying is not advised as they increase the complexity of the process, whereas the added values do not exist or do not outweigh the energetic or quality downsides.