Alginate Oligosaccharide Treatment Delayed Postharvest Blueberry Softening by Modulating Water Mobility and ROS Metabolism

Abstract Blueberries last a short storage time at 20 °C after harvest, rapidly softening and deteriorating. This study demonstrates that treatment with alginate oligosaccharide (AOS) could effectively retard this softening process. AOS treatment slowed down the loss of water inside the fruit, and enhancing the enzymatic activity and gene expression of antioxidants (SOD, CAT, POD, APX) to reduce the accumulation of O2–, H2O2, and MDA. Concurrently, it downregulated the activities and gene expression of cell-wall-degrading enzymes (PG, Cx, β-Gal, β-Glu), which helped preserve cell-wall integrity, maintain fruit firmness, and delay softening. Furthermore, AOS treatment reduced weight loss and decay rate, stabilized soluble solids and acidity, and maintained fruit quality. Overall, the AOS treatment coordinated cell wall and ROS metabolism, and delayed softening, offering a practical strategy for extending blueberry postharvest life.