Nitric oxide treatment delays quality deterioration and enzymatic browning of Agaricus bisporus via reactive oxygen metabolism regulation

Nitric oxide (NO) is a highly reactive gaseous small molecule that regulates plant growth. Sodium nitroprusside (SNP) was used as an NO donor to study the effects of NO treatment on browning and antioxidant activity of button mushrooms (Agaricus bisporus). The findings revealed that exogenous NO treatment alleviated the browning, decreased hardness, and increased weight loss of mushrooms stored at 4 degrees C for 15 days, and reduced the accumulation of reactive oxygen species and membrane lipid peroxidation. Moreover, exogenous NO treatment dramatically increased the anabolism of endogenous NO, maintained the content of antioxidant substances including flavonoids and total phenols, and kept catalase and superoxide dismutase activities at a high level. Further studies revealed that exogenous NO treatment inhibited the activities of enzymes that are involved in browning, which including polyphenol oxidase (PPO) and tyrosinase (TYR), and increased phenylalanine ammonia-lyase (PAL) activity, with SNP treatment at 0.05 mM being the most effective. Furthermore, SNP treatment at 0.05 mM also inhibited PPO and TYR gene expressions while increasing PAL gene expression. Therefore, our findings suggest that exogenous NO has the potential for development in delaying postharvest browning and maintaining the quality of mushrooms.