Improving blueberry cold storage quality:the effect of preharvest hexanal applicationon chilling injuries and antioxidant defensemechanisms

Abstract

Blueberries are vulnerable to chilling injury (CI). This can lead to limited longevity when they are subjected to cold storage con-ditions. This study investigated the effectiveness of a preharvest spray containing 0.02% hexanal in reducing CI and improvingthe postharvest storage quality of ‘Star’ and ‘Biloxi’ blueberries. The blueberries were stored for a period of 5 weeks at 2 °C andin 90% relative humidity (RH). The findings revealed that the preharvest hexanal spraying of both cultivars delayed senescenceby mitigating CI, as evidenced by the bolstering of the antioxidant defense system through increased superoxide dismutase(SOD), ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), and phenylalanine ammonia lyase (PAL) enzyme activity.The treated fruit also maintained elevated levels of total phenol content (TPC), total flavonoids (TFC), and vitamin C, demon-strating enhanced free radical scavenging capacity (FRSC), while exhibiting reduced polyphenoloxidase (PPO) activity, andreduced malondialdehyde (MDA), and H2 O 2 content in comparison with the control group. The preharvest hexanal treatmentalso suppressed fruit softening by maintaining greater firmness and higher membrane stability index (MSI) scores, inhibitingthe activity of polygalacturonase (PG), pectinmethylesterase (PME), xylanase, and ⊍-amylase, and reducing microbial counts(MC) and incidence of decay (DI) in comparison with the control. Preharvest hexanal treatment also improved the overall stor-age quality by reducing weight loss, total soluble solids (TSS), pH, and the TSS/acid ratio, while increasing titratable acidity(TA) in comparison with the control during cold storage. The findings suggest that hexanal, as a preharvest application, delayssenescence effectively and preserves overall quality by enhancing cold tolerance through antioxidant defense mechanisms inblueberry storage under cold conditions.