Development of a composite coating activated with Kurtzmaniella quercitrusa for controlling postharvest citrus green mold

Antagonistic yeasts are acknowledged as eco-friendly alternatives to chemical fungicides for controlling postharvest diseases. However, their practical application is frequently constrained by limited survival, inadequate stability, and brief persistence under storage conditions. This study develops a gelatin/trehalose/sodium alginate (Gel/Tre/SA) coating incorporating the biocontrol yeast Kurtzmaniella quercitrusa , aiming to enhance yeast viability during storage and improve efficacy against postharvest diseases in citrus. The formulation was optimized through an assessment of yeast growth and viability, followed by a systematic characterization of the K. quercitrusa /Gel/Tre/SA composite film. This characterization encompassed analyses of physical characteristics, including rheological behavior, mechanical and barrier properties, microstructure, and wettability on citrus fruit surface. The composite film effectively preserved yeast viability and demonstrated notable in vitro antifungal activity against Penicillium digitatum . In practical applications on citrus fruit, the K. quercitrusa /Gel/Tre/SA composite coating with 0.75% SA reduced the incidence of green mold by approximately 50% after 5 d of storage and decreased the natural decay incidence by about 10% after 35 d. Furthermore, the coating established a semi-permeable physical barrier on the fruit surface, significantly mitigating water loss and postponing the deterioration of postharvest quality. Overall, K. quercitrusa /Gel/Tre/SA composite film enhanced both the stability and biocontrol efficacy of antagonistic yeasts while simultaneously maintaining the quality attributes of citrus fruit. This study offers a practical and scalable approach for implementing yeast-based biocontrol agents in postharvest applications for fruit preservation.