Gallic acid reduces pericarp browning of litchi fruit during storage

Abstract

Litchi (Litchi chinensis Sonn.) as a subtropical fruit tree exhibits high nutritional and economic value. Unfortunately, rapid pericarp browning of litchi fruit after harvest considerably reduces its commercial value. In this study, litchi fruit were treated with gallic acid as a polyphenol with strong antioxidant properties, and then stored at ambient temperature (23 ± 1 °C). It was found that treatment with 5 mmol L⁻¹ gallic acid significantly maintained anthocyanin content and delayed pericarp browning during storage at ambient temperature. Compared with non-gallic acid-treated (control) fruit, the gallic acid-treated fruit showed higher red color value, ATP and energy levels, flavonoid and anthocyanin contents, lower accumulation of H₂O₂ and higher antioxidant capacity during storage, in agreement with higher activities of antioxidant enzymes (superoxide dismutase and peroxidase), and reduced glutathione content. Furthermore, the transcript levels of the genes related to the anthocyanin biosynthesis pathway, such as LcPAL, LcCHS1, LcANS1, LcANS2, LcUFGT3, and LcUFGT4, were significantly increased in the pericarp of the gallic acid-treated litchi during storage at ambient temperature. Thus, it was suggested that the gallic acid treatment can help to maintain the redox equilibrium and energy status, and enhance the anthocyanin biosynthesis, resulting in reduced pericarp browning of litchi during storage. These results provide new insights into the use of gallic acid as a postharvest technology to improve the quality of litchi fruit during storage at ambient temperature.