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

✍ Scribed by Jiang, Yueming; Fu, Jiarui; Zauberman, Giora; Fuchs, Yoram

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 92 KB
• Volume: 79
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(19990515)79:7<950::aid-jsfa289>3.0.co;2-e

✦ Synopsis

Polyphenol oxidase (PPO, EC 1.10.3.2) was puri®ed to homogeneity from litchi peel yielding a single protein with a molecular weight of about 75.6 kD by Sephadex G-100 gel ®ltration, and a 108fold puri®cation of PPO achieved. The enzyme was determined to be composed of two similar subunits. Glutathione, L-cysteine and citric acid suppressed PPO activity markedly, whereas ascorbic acid and n-propyl gallate showed a little inhibition. Moreover, the effect was enhanced by the addition of citric acid. On the basis of the inhibition of PPO activity in vitro, the use of 10 mmol l À1 glutathione and 100 mmol À1 l citric acid was found to give good control of the browning of litchi fruit, and an 80±85% inhibition of PPO activity was observed. It is suggested that application of glutathione in combination with citric acid may slow down the browning of litchi fruit.