Postharvest α-lipoic acid treatment delayed the softening of strawberry fruit by regulating cell wall and energy metabolism

Abstract

After ripening, strawberry fruit is prone to softening, which seriously affects its commercial value. This study investigated the effects of α-lipoic acid (α-LA) treatment on firmness, cell wall metabolism, and energy metabolism of postharvest strawberry fruit. The results demonstrated that 0.5 g L⁻¹ α-LA treatment significantly delayed the softening process by decreasing the content of water-soluble pectin (WSP) and increasing the contents of chelate-soluble pectin (CSP), sodium carbonate-soluble pectin (NSP), hemicellulose, and cellulose. Furthermore, α-LA treatment significantly reduced the activities of polygalacturonase (PG), pectin methyl esterase (PME), β-galactosidase (β-GAL), and cellulase (Cx), and the expression levels of FaPG1, FaPME1, and Faβ-GAL4. α-LA treatment enhanced the activities of H⁺-ATPase, Ca²⁺-ATPase, cytochrome c oxidase (CCO), and succinic dehydrogenase (SDH), thereby maintaining higher ATP and energy charge levels. The upregulation of related gene expression further confirmed that α-LA maintained energy supply, which was essential for maintaining cell wall structural integrity and delaying softening. These findings indicated that α-LA delayed the softening of strawberries by inhibiting cell wall component degradation and promoting energy metabolism, demonstrating its potential as a postharvest preservation strategy.