Introduction

Stropharia rugosoannulata (S. rugosoannulata) ranks among the top ten internationally traded edible mushrooms (Xue et al., 2024), with its high valuation attributable to a combination of delicate flavor, an exceptional nutritional profile, and notable medicinal properties (Liu et al., 2024). Its recognition by the Food and Agriculture Organization (FAO) as a suitable crop for cultivation in developing countries (Askar et al., 2025) has contributed to a steady expansion of its cultivation area in recent years (Yu et al., 2026). Nevertheless, the commercialization of fresh S. rugosoannulata is severely constrained by its inherent perishability. Postharvest deterioration is characterized by pileus discoloration, rupture, stipe shrinkage, and the emergence of white flocculent mold (Zhang et al., 2025). The situation is further complicated by resilient spoilage fungi, including Fusarium pseudoanthophilum, Aspergillus niger, Rhizopus azygosporus, and Talaromyces purpureogenus (Liu et al., 2024). Although a range of preservation strategies, such as short-term anaerobic treatment (Liu et al., 2024) and appropriate sub-freezing temperatures (Xue et al., 2024), has been explored, effective preservation technologies specifically tailored to S. rugosoannulata remain limited, underscoring the necessity for innovative storage solutions.

Edible coating technology has emerged as a promising approach for mushroom preservation (Zhang et al., 2024). Among coating materials, chitosan (CS) has garnered widespread attention for its excellent film-forming ability, antimicrobial activity, and biodegradability (Jiang et al., 2012). However, the inherent hydrophilicity of CS represents a major limitation, compromising its efficacy in moisture regulation and structural maintenance. The incorporation of titanium dioxide (TiO₂) nanomaterials into CS (CS/TiO₂) has been demonstrated to enhance the physical and mechanical properties of the resulting composite (Surendhiran et al., 2022). Previous investigations have shown that CS/TiO₂ nanofilms are effective in mitigating oxidative processes and thereby delaying the postharvest senescence of Agaricus bisporus (Sami et al., 2021). A critical drawback of TiO₂, however, lies in its reliance on UV light for antibacterial activation, which restricts its applicability in typical postharvest storage environments. A promising strategy to overcome this limitation is nitrogen (N) doping, which extends the photocatalytic activity of TiO₂ into the visible light region. N is considered a suitable dopant due to its small atomic size, low ionization energy, high stability, and structural similarity to oxygen, enabling its incorporation into the TiO₂ lattice without altering the crystal structure (Chakraborty et al., 2023). While the preparation of CS/N-TiO₂ composites via co-precipitation has been previously reported for the degradation of patulin in apple juice (Huang & Peng, 2021), their application in mushroom preservation remains unexplored. Moreover, the combination of such nanocomposites with additional antimicrobial agents offers the potential for synergistic inhibition of the specific spoilage fungi associated with S. bisporus.

Against this background, the present study introduces the application of CS/N-TiO₂ composite films for the postharvest preservation of S. rugosoannulata. To further enhance preservation efficacy, four antimicrobial agents, natamycin (NT), nisin, ε-polylysine (ε-PL), and tea polyphenols (TP), were screened for their activity against the previously identified spoilage fungi and incorporated into the CS/N-TiO₂ matrix. A systematic evaluation was conducted on the microstructural characteristics and barrier properties (water vapor transmission rate, oxygen transmission rate, and mechanical strength) of the resulting composite films. Subsequently, the preservation efficacy of the optimized coating was assessed across three storage temperatures (4 °C, 10 °C, and 25 °C), with lightness (L*), weight loss rate, and decay rate employed as core quality indicators. We hypothesized that the preservation mechanism of the composite coating is temperature-dependent. To investigate this, correlation analyses were performed on respiratory intensity, total colony count, malondialdehyde (MDA) content, and the activities of catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO), and superoxide dismutase (SOD). Furthermore, random forest risk ratio and Cox proportional hazards models were utilized for the prediction of storage period under varying conditions. The aim of this study is to realize the regulation of the optimal fresh-keeping effect of the composite film when storing S. rugosoannulata at different temperatures, clarify the differences in the mechanism of the composite film under different temperature scenarios, and provide a scientific theoretical basis and practical technical support for the efficient and long-term storage of S. rugosoannulata under multi-temperature gradients.