Litchi (Litchi chinensis Sonn.) is an important emerging fruit crop of Pakistan with good production potential. Rapid pericarp browning is the main postharvest issue which reduces its cosmetic and market value, limits its extended storage life and causes losses during its transportation and marketing. This integrated research was planned to check the influence of cultivars, harvest locations, exogenous application of chemicals such as oxalic acid, ascorbic acid, hexanal on pericarp browning and fruit quality of litchi under cold storage conditions. The experiments accordingly followed the experimental designs with factorial arrangements. The fruit were stored for 28 days with 7 days sampling interval to determine fruit weight loss (%), pericarp browning index; whereas, soluble solid concentrations (SSC), titratable acidity (TA), SSC: TA ratio and ascorbic acid were determined from juice samples obtained from pulp tissues. Moreover, total phenolics (TP), total antioxidants, activities of peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) enzymes were also determined at 7 days interval during cold storage in both peel as well as pulp tissues of litchi fruit. However, activities of polyphenol oxidase (PPO) enzyme and anthocyanin contents were determined only from peel tissues. The results of first experiment suggested that the cultivars and harvest locations significantly influenced pericarp browning and physico-chemical quality attributes along with the activities of antioxidative enzymes in litchi fruit. Fruit of litchi cultivar ‘Gola’ exhibited superior quality characteristics than ‘Serai’; while, litchi fruit harvested from Haripur location showed better quality than Lahore. Based on the results of the first experiment, litchi cv. ‘Gola’ fruit produced at Haripur location were selected for rest of the experiments. In second experiment, postharvest application of oxalic acid was tested on pericarp browning and fruit quality of litchi cv. ‘Gola’ fruit. Exogenous application of 2 mM oxalic acid delayed pericarp browning, maintained better physico-chemical attributes along with the higher activities of antioxidative enzymes (SOD and CAT) in litchi cv. ‘Gola’ fruit during cold storage. Third experiment was carried out to investigate the effect of postharvest application of ascorbic acid on pericarp browning and fruit quality of litchi cv. ‘Gola’ fruit. Application of 45 mM ascorbic acid improved fruit quality by maintaining better physico-chemical attributes and delayed pericarp browning along with higher activities of antioxidative enzymes (SOD and Abstract XX CAT) in litchi cv. ‘Gola’ fruit during cold storage. In fourth experiment, influence of hexanal fumigation on the storage life and pericarp browning of litchi cv. ‘Gola’ fruit was investigated. Hexanal fumigation could not control browning during cold storage period. Even control fruit showed less pericarp browning than hexanal fumigated fruit. However, among hexanal treatments, 250 μL treatment showed better fruit quality attributes by maintaining higher activities of antioxidative (CAT and SOD) and lower activities of PPO and POD enzymes. From above trials, best concentrations of different chemicals (2 mM oxalic acid, 45 mM ascorbic acid or 2 mM oxalic acid + 45 mM ascorbic acid + 250 μL hexanal) were screened and these were re-confirmed on cv. ‘Gola’ along with another commercial litchi cv. ‘Bedana’. Evidently, 2 mM oxalic acid was more effective in controlling pericarp browning, improving fruit quality and storage life of ‘Gola’ and ‘Bedana’ litchi fruits, as compared to other chemical treatments. Application of 2 mM oxalic acid suppressed the activities of pericarp browning enzymes (PPO and POD) and increased the activities of antioxidative enzymes (CAT and POD). In conclusion, 2 mM oxalic acid or 45 mM ascorbic acid were most effective in delaying pericarp browning and improving quality of litchi fruit (cvs. ‘Gola’ and ‘Bedana’) under cold storage conditions.
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