Inhibition of polyphenol oxidase and the browning control of litchi fruit by glutathione and citric acid

Polyphenol oxidase (PPO, EC 1.10.3.2) from litchi peel was partially purified by ammonium sulfate fractionation and gel filtration, and a 16-fold purification of PPO achieved. The use of 10 mmol litre−1 glutathione and 100 mmol litre−1 citric acid was found to give good control of the browning of litchi fruit and 80–85% inhibition of PPO observed. Application of glutathione in combination with citric acid is recommended as a way of slowing the browning of litchi fruit.