Polyethylene shrink film reduced pitting type chilling injury in ‘Marsh’ grapefruit (Citrus paradisi Macf.) stored at low temperatures. The film did not restrict heat exchange between the fruit and air in the storage room. Chilling injury occurred most rapidly in fruit stored at 5° and 7.5°C, but after 5 weeks the severity of injury was greatest in fruit stored at 2.5°. The pattern of response to temperature was the same for unsealed fruit and sealed fruit. Prestorage conditioning of the fruit for 8 days at 21° prior to storage at 5° reduced chilling injury. Restricting moisture loss with shrink film during the prestorage conditioning treatment did not negate the beneficial effects of conditioning. Restricting moisture loss following chilling had no effect on chilling injury. Thus, although moisture loss is a contributing factor, it does not appear to be the primary factor in chilling injury of grapefruit. In order to minimize chilling injury, moisture loss should be prevented during fruit exposure to chilling temperatures.
Freeze-damaged ‘Marsh’ grapefruit (Citrus paradisi Macf.) and ‘Pineapple’ orange [Citrus sinensis (L.) Osbeck] fruit were sealed in polyethylene shrink film and stored for 6 weeks at 15°C in an attempt to prevent segment dehydration. Although the film greatly restricted water loss from the fruit, segment dehydration was similar to that observed for waxed fruit. During dehydration of freeze-damaged segments of ‘Valencia’ orange fruit, the relative water content of the adjacent mesocarp tissue increased. However, no differences were found in the soluble carbohydrate levels in mesocarp tissue adjacent to damaged and undamaged segments. The results indicate that the mesocarp tissue is not only in the pathway of water loss from free-damaged citrus fruit, but also accumulates water from damaged tissues. Furthermore, segment tissue membranes and walls appear to be differentially permeable to sugars and water.