Modulating the spatiotemporal dynamics of starch metabolism in postharvest sweetpotato using high voltage alternating...

Although postharvest starch degradation was extensively studied, its initiation site and distribution patterns remain unclear. This study investigated the spatiotemporal dynamics of starch metabolism in sweetpotato tubers along vertical (top, middle, bottom) and radial directions (phloem, outer xylem, inner xylem) under 4 kV·m^-1 high voltage alternating electric field (HVAEF) treatment stored at 13 °C for 8 weeks. Results illustrated that starch degradation was first detected in the middle region during early storage, and extended to the bottom and top, whereas HVAEF's inhibitory effect concentrated in the middle and top zones. HVAEF exhibited tissue- and stage-dependent preservation effects, reducing starch content loss by up to 30% in outer xylem at week 4 and reducing soluble sugar accumulation by up to 40% in middle phloem at week 6-8 and middle outer xylem at week 4. Meanwhile, HVAEF was associated with a more uniform spatial distribution of soluble sugar, better preservation of starch granule integrity and cell wall structure, and lower amylase activities. Moreover, HVAEF correlated with downregulated INT1 expression, which showed relatively higher expression tendency in the middle xylem, and upregulated SWEET1 expression, which showed relatively higher expression tendency in the top phloem, suggesting a correlation between HVAEF treatment and tissue-specific carbohydrate redistribution during storage. This study revealed the spatiotemporal characteristics of HVAEF-regulated starch metabolism and highlights its potential as a green physical technology for postharvest quality preservation.