Maintenance of quality and bioactive compounds of cold stored pomegranate (Punica granatum L.) fruit by organic acids treatment.

Pomegranate is a subtropical and chilling sensitive fruit. In this study, the effects of malic acid (50 and 100 mM) and oxalic acid (5 and 10 mM) on quality properties of pomegranate during cold storage (2 ℃) were investigated. The lowest weight loss was observed in fruit treated with 50 mM malic acid. Malic acid had positive effects on color parameters (L*, a*, and b*) of pomegranate at low temperature. Organic acid treatments reduced chilling injury, malondialdehyde, and hydrogen peroxide and increased catalase activity. The lowest activity of polyphenol oxidase and peroxidase was observed in 5 mM oxalic acid-treated fruit. On the other hand, fruit treated with 50 mM malic acid showed the maximum ascorbic acid and citric acid content. The most antioxidant activity was found in fruit treated with 5 mM oxalic acid and 50 mM malic acid. Also, all treatments except 10 mM oxalic acid and 100 mM malic acid resulted in higher titratable acidity than control fruit. Overall, 50 mM malic acid and 5 mM oxalic acid were the most effective for preserving the quality of pomegranate fruit at low temperature.

Maintenance of quality and bioactive compounds in pomegranate fruit (Punica granatum L.) by combined application of organic acids and chitosan edible coating.

Pomegranate is a subtropical fruit that affects its cold storage. To ameliorate chilling injury, fruits were treated with malic acid (50 and 100 mM MA) and oxalic acid (5 and 10 mM OA), and then, coated with 2% chitosan (CH) and stored at low temperature (2°C) for 4 months. Treatments significantly delayed the development of browning signs and reduced malondialdehyde and hydrogen peroxide of arils as compared to control. CH+ 5 mM OA resulted in the highest catalase activity in arils during storage. Anthocyanin, ascorbic acid, total phenolic compound, and antioxidant activity of arils were higher in CH+ 5 mM OA and CH+ 50 mM MA-treated fruit. Also, the minimum PPO and POD activity of arils was found in CH+ 5 mM OA. Overall, CH edible coating following organic acids treatment, and especially 5 mM OA and 50 mM MA are beneficial treatments for preserving the quality of pomegranate fruit during storage. PRACTICAL APPLICATIONS: Pomegranate fruit waste is high due to chilling sensitivity during cold storage. Coating fruit with 2% chitosan (CH) alone and with malic acid (50 and 100 mM MA) and oxalic acid (5 and 10 mM OA) could ameliorate chilling injury. Treatments reduce the development of browning signs. Overall, CH edible coating combined with 5 mM OA and 50 mM MA were the most effective treatments for ameliorating the chilling injury of pomegranate fruit.