Integrated physiological and transcriptomic analysis revealed the regulatory mechanisms of thyme essential oil emulsion treatment in accelerating the browning process of fresh-cut button mushrooms

Button mushrooms are widely consumed worldwide, but prone to browning during postharvest handling. Understanding the browning mechanism is essential for developing effective prevention strategies. This study found that the 0.25% and 1% thyme essential oil emulsion (TEOE) caused rapid browning of fresh-cut button mushrooms, compared to 1% peanut oil emulsion (POE). Physiological and transcriptomic analyses were conducted to determine the underlying mechanism, indicating that the 1% of TEOE group showed a 47.02% increase in the browning index at 7 h and a 62.11% rise in electrical conductivity at 0.25 h compared to the control group (CK, distilled water). Additionally, TEOE treatment significantly inhibited superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia-lyase (PAL) activity, while accelerating that of polyphenol oxidase (PPO) and tyrosinase (TYR) activities. It also increased the malondialdehyde (MDA) content. Notably, the ascorbate-glutathione cycle was involved in this browning process of button mushrooms. Transcriptomic sequencing analysis showed that the differentially expressed genes after TEOE treatment were mainly related to energy metabolism, membrane lipid metabolism, and the MAPK signaling pathway. This study explores the role of TEOE in the postharvest browning process of fresh-cut button mushrooms, which may provide a theoretical foundation for more comprehensive investigations into the browning mechanism.