Enhancing ultrasonic-assisted drying of low-porosity products through pulsed electric field (PEF) pretreatment: The case of butternut squash

Ultrasonic-assisted drying is an effective technique for accelerating drying processes, particularly for products with high porosity. The structural changes induced by pulsed electric field (PEF) treatment can make low-porosity products more susceptible to the effects of ultrasound during drying. This study aimed to investigate the influence of PEF treatment on the structure of low-porosity products, such as butternut squash, and to evaluate its effect on ultrasonic-assisted drying. PEF pretreatment altered the physicochemical and microstructural properties of butternut squash. Thus, the higher the energy input, the higher the cell disintegration rate, the lower the shearing force and the lower the water holding capacity. For the same energy input applied, no influence was observed from the different combinations of pulse number and electric field intensity used. The microstructural analysis also showed greater effects with increasing intensity of PEF treatments. All these changes affected the subsequent drying, increasing the drying rate of conventional drying. Moreover, PEF pretreatment enhanced the ultrasound effects when applied during drying, reducing drying time by up to 47% when moderate PEF intensity was used. Therefore, PEF pretreatment under the appropriate conditions could make ultrasound-assisted drying of low-porosity products, such as butternut squash, more feasible.