Magnetic field delays the senescence of strawberries by maintaining energy state and regulating respiratory metabolism

Strawberries are prone to rapid quality deterioration after harvest. Research has confirmed that a magnetic field can improve fruit quality during postharvest storage. However, how the magnetic field impacts the postharvest physiology of strawberries is far from being explored. In this study, the magnetic field (MF, 4 mT, and 50 Hz) was employed during the storage of strawberries at 4 °C for 1, 3, 5, 7, 10, and 15 d, and conventional refrigeration (CR) was used as the control. The results showed that the MF maintained better fruit quality, as indicated by lower decay incidence, declined weight loss, and greater firmness retention. The decrease in soluble solids content and titratable acidity of strawberries caused by respiratory depletion was also alleviated by MF. Furthermore, an improvement in the adenosine triphosphate level, energy charge, activity of enzymes (H+-ATPase, Ca2+-ATPase, succinate dehydrogenase, and cytochrome oxidase) involved in the respiratory metabolism, as well as primary respiratory metabolites (D-glucose, succinic acid, fumaric acid, and citric acid) were observed for the strawberries of MF group. Accumulations of hydrogen peroxide, superoxide anion, and malondialdehyde were suppressed with the application of MF. Overall, the MF contributed to maintaining higher energy and membrane integrity and function, regulating the levels of energy metabolism enzymes, and mitigating reactive oxygen species accumulation, which might be a part of the mechanism involved in retarding the senescence and decay of harvested strawberries.