Nanocomposite packaging materials delay the browning of Agaricus bisporus by modulating the melanin pathway

Abstract

To elucidate the browning inhibition mechanism of nanocomposite packaging (nano-PM) Agaricus bisporus during cold storage, we analyzed the biophysical and biochemical indices, including substrates, key enzymes, and relative gene expression associated with browning. The results showed that nano-PM could maintain a higher total phenol content and lower flavonoid content of mushrooms throughout the storage period than the commercial polyethylene packaging treatment (control). The activity of phenylalanine ammonia lyase (PAL) and its relative gene expression were inhibited by nano-PM, whereas cinnamic acid-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL) activities were promoted. Nano-PM promoted the synthesis of γ-L-glutaminyl-4-hydroxybenzene (GHB), tyrosine, and catechol, but inhibited the synthesis of soluble quinone, γ-L-glutaminyl-3,4-dihydroxybenzene (GDHB), and 3,4-dihydroxyphenylalanine (DOPA), which were mainly attributed to polyphenol oxidase (PPO), tyrosinase (TYR), and laccase (LAC) activities as well as gene relative expression at low levels. Nano-PM increased the enzyme activities of the phenylpropanoid pathway by activating their relative gene expression, promoting the accumulation of phenolic substances to enhance the resistance of mushrooms to harsh environments. Additionally, nano-PM inhibited TYR activity to delay the conversion of GHB to GDHB and tyrosine to DOPA, which ultimately reduced melanin formation and delayed mushroom browning, leading to a longer shelf life.