Galla rhois water extract inhibits enzymatic browning in apple juice partly by binding to and inactivating polyphenol oxidase

•Galla rhois water extract inhibited the enzymatic browning of apple juice for 16 days.•Galla rhois water extract bind to and inactivate polyphenol oxidase.•Galla rhois water extract is a strong antioxidant that decreases DPPH radicals and elevates ferric reducing antioxidant power.•Gallotannin derivatives are major compounds in Galla rhois water extract.•Among the major compounds of Galla rhois water extract, penta-O-galloyl-β-d-glucose, tetragalloylglucose, epicatechin gallate, methyl gallate, ellagic acid, ethyl gallate, and trigalloylglucose showed anti-PPO activities. Although Galla rhois has been used as a traditional medicine in Asian countries, there was no application of it in anti-browning food additives. Here, we tested whether Galla rhois inhibits apple juice browning. Apple juice browning was blocked at 250–1000 µg/ml of Galla rhois for 16 days but the effect of vitamin C did not last until a day. In vitro assays showed that the antioxidant capacity of Galla rhois was stronger than that of vitamin C. Further analysis by UPLC-MS/MS identified 17 phytochemicals containing gallotannin derivatives. Docking simulation and polyphenol oxidase activity assay indicate that the mechanisms underlying Galla rhois-mediated inhibition of the enzymatic browning include but are not limited to the combined effects of multiple compounds including galloylglucose- and gallate-derivates. Although marketability and long-term toxicity of Galla rhois should be tested, it may be applied as a food additive to elevate food quality.