Enhancing pore structure and nutritional quality of microwave-vacuum dried carrots with pulsed electric fields

Abstract

The development of porous structure in food materials is crucial for enhancing functional properties, such as rehydration and bioactive compound retention. Despite advancements, the influence of processing parameters on physical structure and the combined effects of multiple techniques remains under-explored. The aim of this paper is to investigate the impact of varying pulsed electric fields (PEF) energy inputs on the physical and functional properties of microwave-vacuum dried carrots. Carrots were pre-treated by PEF with the specific energy inputs of 0.5, 1.0, and 2.0 kJ/kg, at a field intensity of 1.07 kV/cm; a control group remained untreated. Carrots were sliced into 4 mm, blanched, frozen, and microwave-vacuum dried. The quality of dried material was assessed through total carotenoid content, antioxidant activity by ABTS assay, total phenolic content, rehydration rate, hygroscopicity, scanning electron microscopy, and micro-computed tomography. It was found that PEF-treated samples exhibited a more uniform distribution of pores compared to the untreated group. The rehydration rate of the untreated samples was 32 % lower than the 2.0 kJ/kg PEF-treated samples, while 1.0 kJ/kg PEF-treated samples demonstrated higher hygroscopicity. Furthermore, the study showed that 2.0 kJ/kg PEF-treated carrots had the highest carotenoid content. However, no significant benefits were observed from PEF treatment in improving antioxidant activity or polyphenol content, with 2.0 kJ/kg PEF-treated carrots showing the lowest levels of both. These results highlight the potential of PEF as a pre-treatment to improve the structural and functional quality of dried food products, offering new possibilities for the development of advanced porous food materials.