Sustainable chitosan/eggshell powder edible coatings for moisture-barrier regulation and shelf-life extension of fresh fruits.

Postharvest water loss and microbial deterioration substantially limit the shelf life of fresh fruits. This study developed chitosan/eggshell powder (CS/ESP) composite films and coatings to improve moisture resistance and fruit preservation while valorizing eggshell waste. ESP was incorporated into a 1.5 wt% CS matrix at 0-20 wt%, and the resulting materials were evaluated for mechanical, barrier, surface, structural, swelling, biodegradation, and preservation properties using cherry tomatoes and grapes. ESP exerted a concentration-dependent effect, with 10 wt% providing the most balanced performance. At this loading, tensile strength and elongation at break reached 21.12 MPa and 48.90%, representing increases of 17.99% and 22.28%, respectively, relative to neat CS. Water vapor permeability decreased from 0.95 to 0.88 g·mm/(h·m2·MPa), the water contact angle increased from 84.6° to 89.9°, and the swelling ratio declined from 49.33% to 10.78%. Structural analyses indicated that well-dispersed ESP promoted a compact CS network, reduced water mobility, and increased moisture-transport tortuosity, whereas 15-20 wt% ESP caused aggregation and interfacial defects. The 10 wt% ESP coating most effectively reduced weight loss and delayed declines in firmness, total soluble solids, and titratable acidity. After 21 d, total viable counts were reduced by 1.72 and 1.78 log CFU/g in cherry tomatoes and grapes, respectively, compared with uncoated controls. After 13 d of soil burial, mass losses of PE, neat CS, and CS/10 wt% ESP films were 0.04%, 11.60%, and 16.84%, respectively. These findings support CS/ESP coatings as a sustainable strategy for fresh-fruit preservation.