EFFECT OF FRUIT MATURITY AND COOL STORAGE ON CHILLING INJURY IN PEACH AND NECTARINE

The effect of peach and nectarine physiological maturity at harvest on severity of chilling injury (CI) expression during cool storage has yet to be fully elucidated. Measurements of index of absorbance difference (IAD) and ethylene production were used to determine fruit maturity classes for Prunus persica (L.) ‘Fire Sweet’ nectarine and ‘Zee Lady’ peach. Harvested fruit was categorized into one of three maturity classes; climacteric, onset climacteric or pre-climacteric using a portable vis-NIR DA-meter. Flesh browning severity in ‘Fire Sweet’ nectarine was low in fruit within all maturity classes after 28 days of storage at 7°C. Flesh bleeding was significantly higher in climacteric fruit compared to pre-climacteric fruit during the first 21 days of storage. At each storage period little difference in flesh texture was detected between maturity classes, but mealiness increased significantly with increasing storage period within all classes. CI severity was marginally higher in ‘Zee Lady’ peach with flesh browning significantly higher in climacteric fruit than in fruit from the other two maturity classes after 14, 21 and 28 days of storage. Increases in peach flesh mealiness scores were marginal during storage but mealiness was significantly higher in climacteric fruit compared to pre-climacteric fruit after 21 and 28 days of storage. In this study CI severity was shown to increase with fruit ripeness at harvest as measured by index of absorbance, and with cool storage period when fruit were stored at a temperature conducive to CI expression. A limitation of this work was the relatively low CI severity found in both cultivars over the storage period. Further work will verify the results obtained here using mid and late season peach and nectarine cultivars with a higher susceptibility to chilling injury.