Mechanisms of ethanol treatment on controlling browning in fresh-cut lotus roots

This study evaluated the changes in phenolic and reactive oxygen species metabolism, and microbial diversity in fresh-cut lotus roots following ethanol treatment to elucidate the potential mechanisms of ethanol in controlling microbial growth and browning. Activity suppression and gene expression downregulation of phenylalanine ammonia-lyase, polyphenol oxidase, and peroxidase took place with ethanol treatment, resulting in the decreased accumulation of total phenols and soluble quinones. The total phenol and soluble quinone contents of ethanol-treated slices were 12.63% and 30.22% lower than those in the control group, respectively, after 12 d of storage. Ethanol treatment changed the level of eleven individual phenols, two of which were associated with antioxidant ability. Besides, the ethanol-treated slices exhibited the reduced production of reactive oxygen species, increased activities of superoxide dismutase and catalase, improved ascorbic acid contents and 1,1-Diphenyl-2-picrylhydrazyl scavenging rate, and the upregulated transcriptional levels of NnGR and NnGST. Moreover, the integrated transcriptomic and metabolomic analyses show the biosynthesis of syringin (an antioxidant in various medicinal plants) might be stimulated by ethanol treatment. Ethanol treatment inhibited the abundance of Pantoea, Pseudomonas, Tolumonas and Stenotrophomonas. These findings suggested ethanol treatment is a simple and potential technology for preserving the quality and antioxidant ability of fresh-cut products.