Abstract: In this paper, fresh-cut sweet potato ‘Yushu No. 17’ was divided into three parts including skin, peripheral and central part. The mechanism of browning in different parts of fresh-cut sweet potato was studied by measuring the browning index, the content of phenolic compounds and the activity of browning-related enzymes. The results showed that chlorogenic acid was the major browning substrate in sweet potato. There were differences in browning among different parts of freshcut sweet potato, with the most severe browning occurring in the skin, followed by the peripheral and central parts. The contents of total and free phenols in the skin were significantly higher than those in the peripheral and central tissues (P < 0.05), with a 3 to 4-fold increase being observed in the content of chlorogenic acid. Polyphenol oxidase (PPO) was the major enzyme responsible for the browning process of skin tissue. L-phenylalanine ammonia-lyase promoted the accumulation of phenolic substances. The browning process of peripheral tissue was catalyzed by PPO and peroxidase (POD), while that of central tissue was mainly caused by POD. The moisture content of sweet potato tissue decreased with storage time.

Key words: fresh-cut sweet potato, enzymatic browning, chlorogenic acid, polyphenol oxidase, peroxidase