Effect of Postharvest Hot Air Treatments on Ripening and Soluble Sugars in Banana Fruits, Musa Spp. ‘Williams’

Abstract

Postharvest hot air treatments have been traditionally used for disinfection and disinfestations of fruits and vegetables. Recently, high temperature preconditioning has been shown to have the potential to impart tolerance to chilling injury in some commodities. In this study, banana fruits were exposed to two hot air treatments (50°C for 10 min and 40°C for 60 min) and then stored for 3 weeks at chilling temperatures (8°C). Thereafter, the fruits were evaluated for chilling injury symptoms and ripening-related physicochemical changes during and after cold storage. Hot air treatments significantly improved the fruits’ tolerance to chilling temperatures but at the same time affected ripening-related changes in the fruits. Immediately after the treatments, the treated fruits exhibited significantly higher respiration rates; approximately 30% higher that the untreated controls. Ethylene evolution was suppressed by as much as five times relative to the untreated controls. However, during cold storage and upon transfer from cold storage to ambient room conditions the treated fruits had respiration rates comparable to the untreated fruits, while ethylene levels were higher in the treated fruits. Cold storage significantly impaired the ripening process in both the treated and untreated fruits. The cold-stored fruits failed to achieve a hue angle low enough to give them the characteristic bright yellow color of optimally-ripened bananas. Similarly, the treated fruits failed to soften sufficiently, thereby maintaining higher pulp and peel firmness compared to the untreated controls at ambient room conditions. These findings show that although hot air treatments are effective in imparting chilling injury tolerance to banana fruits, time × temperature combinations remain a challenge in ensuring optimum ripening and high fruit quality after cold storage.