Combined melatonin and UV-C treatment maintains the quality of fresh-cut bamboo shoots during storage by altering microbial diversity and metabolites

The quality of fresh-cut Ma bamboo (Dendrocalamus latiflorus Munro) shoots was evaluated via physicochemical, 16S rRNA gene sequencing, and metabolomic analyses. Lactobacillaceae, Streptococcaceae, and Enterobacteriaceae were the predominant bacteria. Melatonin and UV-C treatments most inhibited Lactobacillaceae and Cyanobacteriales, respectively. Differential metabolic profiling revealed that 47 and 44 metabolites were downregulated and upregulated, respectively, in the shoots during storage. Significant metabolite accumulation, including secondary metabolite precursors related to phenylpropanoid biosynthesis (tyrosine, leucine, and phenylalanine), was detected. This corresponded to the lignin content and firmness. Melatonin and UV-C treatments increased resistance to external stress via the accumulation of fatty acids and flavonoids. UV-C irradiation upregulated 19 of 22 fatty acyls, including ethyl linoleate, ethyl palmitoleate, 2-isopropylmalic acid, and jasmonic acid, whereas melatonin treatment increased 12 of 16 flavonoids, including hildgardtene and butein 4′-arabinosyl-(1->4)-galactoside. A combined melatonin and UV-C treatment exhibited the merits of both and best maintained the quality of the shoots.