The ameliorative effects of spermidine and calcium chloride on chilling injury in pomegranate fruits after long-term storage

Introduction. Pomegranate fruits (Punica granatum L.) are chilling-sensitive crops. Materials and methods. Pomegranate fruits were treated with calcium chloride and spermidine, alone or in combination, by normal dip and vacuum infiltration methods. The treated fruits were stored at 2 °C for 4 months. At the end of the storage period, samples were held for 3 days at 20 °C, then the qualitative constituents were evaluated. Results and discussion. Treated fruits exhibited less weight loss and higher juice content than control fruits. Non-treated fruits developed chilling injury manifested as an increase in K+ leakage and polyphenol oxidase activity. Calcium chloride and spermidine treatments resulted in lower soluble solid content, but some fruits showed higher titratable acidity. All treatments significantly increased ascorbic acid content. The pH of aril juice in treated fruits was lower than that of non-treated fruits, probably due to higher titratable acidity. Total antioxidant activity and total phenolic content increased in treated fruits. In our study, a correlation was observed between total phenolic content and total antioxidant activity. Conclusion. The treatments applied in our experiments maintained overall quality of pomegranate fruits during long-term storage. Postharvest application of calcium and spermidine either alone or in combination could ameliorate adverse effects of low temperature on pomegranate fruit quality during cold storage. Vacuum infiltration was as effective as the normal dip method. However, normal dip is a simpler and faster treatment method.