Preserving Pomelo Quality: Sodium Alginate Coating Containing Bacillus subtilis for Sustained Antifungal Activity

Wendan pomelo (<i>Citrus maxima</i>), valued for its unique quality and high nutritional value, is susceptible to postharvest decay caused by mechanical damage and fungal infection. This study developed a bio-based preservation strategy by incorporating <i>Bacillus subtilis</i> (<i>B. subtilis</i>) into a sodium alginate (SA)-based coating. An antagonistic <i>B. subtilis</i> strain, isolated from the pomelo growth environment, demonstrated effective inhibition against the pathogenic fungi <i>P. digitatum</i> and <i>P. italicum</i>. The <i>B. subtilis</i>/SA (2.0%) coating maintained high bacterial viability without adversely affecting the viscosity, gas barrier properties, or mechanical strength of the film. The application of the <i>B. subtilis</i>/SA coating significantly delayed fruit appearance deterioration, pulp softening, and decay in pomelo. Furthermore, the treatment enhanced flavonoid accumulation and increased the activity of antioxidant enzymes, thereby maintaining quality and extending storage life to 90 d. This study provides an effective bio-preservation strategy for the postharvest management of pomelo.