Influence of fruit maturity on antioxidant potential and chilling injury resistance of peach fruit (Prunus persica) during cold storage

Postharvest handling of peach (Prunus persica) fruits is challenging as they deteriorate quickly under ambient conditions. Cold storage slows detrioration but causes chilling injury (CI), reducing quality of fruits. To overcome this challenge the influence of fruit maturity on antioxidant capacity and CI development in “Ryan sun” peach fruits was investigated. Fruits were harvested from commercial farms in Lleida in Spain. Optimum harvest date (OHD) was determined on-tree visually by ground skin colour when 70% of skin turned reddish using colour discs. Fruits were harvested 7 days before OHD (OHD-7) and seven days after OHD (OHD+7) with OHD fruits serving as control. The fruits were stored at 5 oC for 15, 30 and 45 days. Fruits were evaluated for CI manifestations such as lack of juiciness (wooliness) and flesh bleeding. The lack of free juice released upon crushing fruit flesh through cheese cloth reveals symptoms of wooliness. Percentage CI resistance was calculated (100% - %CI incidence) for each group. Antioxidants were extracted and analysed using the Ferric Reducing Antioxidant Property (FRAP) method. Fruits harvested earlier (OHD-7) recorded the highest antioxidant capacity of 1.080 mgTE/g followed by control fruits (OHD) with antioxidant capacity of 0.976 mgTE/g. Fruits harvested late (OHD+7) recorded the lowest antioxidant capacity of 0.471 mgTE/g. After 15 days of cold storage, OHD resisted CI by 70% followed by OHD+7 (60%) and OHD-7 fruits (55%). After 30 days of storage, OHD-7 fruits recorded 0 resistance to CI but OHD and OHD+7 fruits resisted by 20% each. Fruits of all harvest dates showed no resistance to CI after 45 days of storage. Fruit maturity and cold storage length were found to significantly (P< 0.05) influence CI resistance. For good keeping quality, “Ryan sun” peach fruits should be harvested mature for long keeping but harvested earlier when intended for best antioxidant property.Key words: chilling injury, antioxidants, fruit maturity