Study on Browning Degree of Fresh-cut Purple Sweet Potato and its Inhibition during Storage.

The basic study on activity of polyphenol oxidase (PPO) from purple sweet potato (PSP) and its control method was mainly carried out by spectrophotometry. The PPO activity and browning degree (BD) of PSP peel were higher than those of inner-tissue and intact sweet potatoes. The relativity between them was positive, and relativity coefficient was 0.9895. The activity of PPO extracted from sliced PSP increased initially and decreased afterwards, with the highest activity of PPO on the third day during storage. And BD increased very quickly as time went by, especially in the first three days. The relativity between PPO activity and BD was negative, and relativity coefficient was -0.8747. The result indicated that the browning of fresh-cut PSP slices during storage was mainly due to PPO in it. The composite inhibitor was optimized by the orthogonal design, and the addition of 0.05% L-cysteine+0.03% phytic acid+0.3% ascorbic acid+0.3% citric acid would markedly inhibit the enzymatic browning caused by PPO and improve the quality of fresh-cut PSP slices.