Exposure to low ethylene concentrations in supply chain conditions cause differential quality attributes in 'SunGold™' kiwifruit

Ethylene (C₂H₄) concentrations in the supply chain can increase within a kiwifruit package and the surrounding storage atmosphere, as a result of high ethylene producing rotting fruit or other sources of contamination e.g., exhaust fumes. Earlier studies have demonstrated that low ethylene concentrations during cool storage, limit the storage life of other kiwifruit cultivars. However, the influence of potential brief exposures in the supply chain is less known. This study aimed to investigate both continuous and brief exposures of Actinidia chinensis 'SunGold™', to exogenous ethylene within the coolchain. The effects on the fruit quality (firmness, flesh colour, and soluble solids content) were determined. The fruit was first stored in air for 10 weeks at 1°C to simulate the well-controlled ethylene free (

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0.001 µL L^-1) on-shore storage environment. The fruits were then exposed to either a continuous concentration of ethylene (0.01, 0.06 or 1 µL L^-1) for 14 weeks or exposed to 0.06 µL L^-1 ethylene for 3, 7, or 14 d before returning to air storage. Constant air storage (

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0.001 µL L^-1 C₂H₄) was used as a control. The subsequent quality assessments were conducted fortnightly. Continuous exposure resulted in accelerated firmness reduction for all treatments and an increase in the flesh hue angle for fruit exposed to 1 µL L^-1. However for those fruits briefly exposed to ethylene at 0.06 µL L^-1 for up to 2 weeks, no subsequent effects on the quality were observed. The results suggest a need to investigate ethylene exposure concentration × time thresholds for obtaining a quality effect, given that the 0.06 µL L^-1 continuous treatment differed from the control after 4 weeks. The interaction of ethylene exposure in combination with environment temperature breaks would also be interesting to pursue. Together these insights will assist in developing realistic guidelines of how to manage and react to ethylene and temperature exposures in a commercial coolchain.