Effect of hot-air treatment on the ripening of ‘Qingnai’ plum (Prunus salicina Lindl.)

Abstract

Summary‘Qingnai’ plums are popular as “green” fruit throughout south-east Asia. However, the fruit soften rapidly after harvest, limiting commercial exports from China. Traditionally, the crop is sold mostly to the local population. We evaluated the potential of hot-air treatment (HAT) to delay ripening of ‘Qingnai’ plum fruit as a potential technology to expand the marketing of “green” plums. Fruit were stored at 20°C after being exposed to 20°C (control), 40°C (HAT40), 45°C (HAT45), or 50°C (HAT50) air for 5 h. Information was collected on fruit firmness, peel colour, chlorophyll contents, chlorophyllase activities, soluble solids contents (SSC), titratable acidities (TA), the rates of respiration and ethylene production, and the activities of cell wall hydrolysing enzymes. Fruit softening was accompanied by a progressive decrease in hue angle (h°), chlorophyll content, and TA, and increases in chlorophyllase, pectin methylesterase (PME) and polygalacturonase (PG) activities. Hot-air treatment delayed the onset of the climacteric peaks of CO2 and ethylene production, delayed fruit softening, and delayed the peaks of PME and PG activities. Heat-treated fruit changed from green-to-yellow at a slower rate than control fruit, with a delay in the peak of chlorophyllase activity. Heat-treated fruit could be stored for up to 18 d, and non-treated fruit for only 12 d. These results suggest that HAT can extend the post-harvest life of ‘Qingnai’ plums by up to 6 d.