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Effects of a pure oxygen atmosphere on enzymatic browning of harvested litchi fruit

Summary Pericarp browning and decline in fruit quality are major problems of harvested litchi fruit. The effects of a pure O2 atmosphere on enzymatic browning and quality of harvested litchi fruit were investigated. Litchi fruit were kept in air or pure O2 for 6 d at 28°C. Changes in browning, polyphenol oxidase (PPO), anthocyanase, total soluble solids, titratable acidity and ascorbic acid were monitored. Effects of pure O2 on in vitro activities of PPO and anthocyanase were also evaluated. Exposure of litchi fruit to pure O2 significantly (P≤0.05) reduced skin browning during storage. Pure O2 inhibited the activities of PPO and anthocyanase which may account for browning inhibition. Furthermore, pure O2-treatment inhibited the in vitro activities of PPO and anthocyanase during incubation for 4 h. Litchi fruit exposed to pure O2 for 6 d had higher total soluble solids and titratable acidity than those kept in air, but lower ascorbic acid. Thus, application of pure O2 effectively reduced skin browning and maintained high total soluble solids and titratable acidity levels of pulp in harvested litchi fruit.