Short-term warming inhibits polyphenol oxidase activity and influences free amino acid accumulation and de novo synthesis of tyrosine in fresh-cut potato

Potatoes cut immediately after being taken out from cold storage easily undergo browning. Researchers have reported that long-term warming alleviates the browning of fresh-cut potatoes. However, long-term warming is not commercially applicable. The present study investigated the effect of short-term warming (SW) at 25 °C for 12 h on the browning of fresh-cut potatoes. The browning index of potatoes stored at 4 °C for 8 months was tested. The analysis revealed that SW efficiently blocked enzymatic browning by inhibiting polyphenol oxidase (PPO) activity, decreasing total phenolic content and malondialdehyde (MDA) content, and increasing peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activity, and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and 2,20-azino-bis (3-ethylben zothiazoline) 6-sulphonic acid (ABTS) inhibition rates. Moreover, SW treatment induced the expression of the serine protease inhibitor (SPI) gene and enhanced SPI activity, increased the soluble protein content and decreased free tyrosine, and lysine content in fresh-cut potatoes during the 5 d storage at 2∼4 °C. The contents of glutamic acid, aspartic acid, and proline in the fresh-cut potatoes increased after SW treatment. Furthermore, the amino acid complementation experiments showed that tyrosine and lysine aggravated browning while glutamic acid and aspartic acid reduced browning. The SW treatment reduced the activity of chorismate mutase (CM), repressed the transcript levels of CM synthesis-related genes (CM1 and CM2), and inhibited free tyrosine synthesis. These results indicate that SW treatment alleviates the browning of potato tubers after cold storage probably due to its influence on PPO, metabolism of tyrosine, other FAAs and phenolics, and antioxidants.