Synergistic vacuum steam pulse blanching and gliding arc cold plasma pretreatment enhances drying efficiency and folate retention in Yardlong bean pods.

Yardlong bean (Vigna unguiculata subsp. sesquipedalis) pods are rich in folate and bioactive compounds but suffer quality deterioration during hot-air impingement drying. This study evaluated vacuum steam pulse blanching (VSPB), gliding arc cold plasma (CP; 30-120 s), hot water blanching, and sequential VSPB-assisted CP (B-CP) pretreatments for improving drying efficiency and quality retention. Among combined treatments, VSPB followed by 30 s CP exposure (B-CP30) was optimal because it significantly accelerated moisture removal while maintaining structural integrity and high folate retention (p < 0.05). B-CP30 enhanced surface porosity, reduced contact angle, improved membrane permeability, and promoted uniform moisture redistribution, thereby reducing drying resistance and shortening drying time compared with untreated samples (p < 0.05). Longer plasma exposures caused excessive structural and oxidative damage. Pretreatment significantly affected shrinkage, rehydration ratio, folate, total phenolics, and flavonoids after drying (p < 0.05). Short-duration B-CP is therefore promising for high-quality dried yardlong bean pods.