Exogenous proline treatment inhibiting enzymatic browning of fresh-cut potatoes during cold storage

Abstract

Fresh-cut potato slices are prone to browning, resulting in a severely reduced commodity value. Hence, a safe and effective method to inhibit the browning of fresh-cut potatoes is urgently needed. In this study, we investigated the effect of pre-treatment with a proline solution on browning, polyphenol oxidase (PPO) activity, total phenol content, antioxidant activity, and free amino acid content of fresh-cut potatoes. The results showed that pre-treatment with 90 mmol L−1 proline for 1 h at 30 °C reduced browning and surface dehydration, improved the overall visual aspect, and extended the shelf-life of potato slices to 4 d at 2−4 °C. The PPO activity and total phenol content in pre-treated potato tubers and slices were lower than control and water treatment. The superoxide dismutase (SOD), catalase (CAT) activities, the percentage inhibition of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,20-zo-bis-3-ethylben zothiazoline-6-sulfonic acid (ABTS), and the Fe2+ reduction capacity had increased compared with control and water treatment. Compared with control and water treatment, the tyrosine, aspartic acid, glutamic acid, serine, glycine, histidine, and valine content were reduced, whereas proline, histidine, and valine had increased. Mechanistically, pre-treatment with proline inhibited the browning of fresh-cut potatoes by reducing PPO activity, total phenolic content, and the content of several amino acids, while inducing the accumulation of intrinsic proline content and increasing the antioxidant capacity of fresh-cut potatoes.