Effect of Red Visible Lighting on Postharvest Ripening of Bananas via the Regulation of Energy Metabolism

The mechanism by which LED red light irradiation regulates postharvest banana ripening was evaluated in this study by the continuous irradiation of banana fruits at the mature-green stage. In this study, a self-developed LED banana fresh-keeping container lid was used to continuously irradiate the immature banana fruit. The light wavelength was 655.0 ± 1.0 nm, the light intensity was 800.0 ± 10.0 LX, and the height between the LED lamp and the fruit was 15.0 ± 0.5 cm. Bananas stored under dark conditions were used as the negative control group, and bananas stored under dark conditions after spraying with 500.0 mg/L ethephon diluent were used as the positive control group. Changes in physiological parameters related to postharvest banana ripening, such as the respiration rate, ethylene release, texture, color, carotenoid content, chlorophyll content, adenosine triphosphate content, and energy metabolism-related enzyme activities, were measured during 8 days of storage at 20.0 ± 0.1 °C to analyze the key factors determining postharvest banana ripening in response to red light. The red light-irradiated bananas had higher total color differences and higher rates of chlorophyll degradation and carotenoid synthesis than those of the ethephon-treated group during the storage period. Red light irradiation promoted banana fruit ripening and senescence mainly by promoting carotenoid synthesis, capturing absorbed light energy, accelerating energy metabolism, effectively enhancing the activities of the respiratory and energy metabolism-related enzymes H⁺ adenosine triphosphatase, Ca²⁺ adenosine triphosphatase, succinate dehydrogenase, cytochrome C oxidase, and malic enzyme, and promoting organic acid degradation. In conclusion, LED red light can be used as a new physical ripening technology for bananas, with a similar effect to that of traditional ethephon treatment.