Application of gelatin-silver nanocomposite film as an active packaging material in toast bread

Biodegradable gelatin coating embedded with different concentrations (1, 3 and 5%) of silver nanoparticles (AgNPs) designed as an antimicrobial packaging system to improve the quality of toast bread samples and prolong their shelf life when stored at room temperature for a 5-day period. The findings revealed a significant enhancement in the physical (film thickness, solubility, water vapor permeability, oxygen permeability) and mechanical (tensile strength and elongation at break) properties of the gelatin-based films upon the integration of AgNPs up to 3% (P < 0.05). SEM analysis displayed a homogeneous structure in the nanocomposite films when AgNPs were integrated at concentrations ≤ 3%. This was complemented by the confirmation of the interaction between the polymer and nanoparticles, as well as the crystallinity of AgNPs in the film, validated through FT-IR spectroscopy and XRD respectively. The evaluation of physicochemical and microbial characteristics of the coated bread revealed that samples containing 3% of AgNPs effectively preserved moisture content and water activity, minimized bread firmness and staleness, thereby maintaining the lightness index (L*) of the crust/crumb in comparison to the control (gelatin alone). Furthermore, all actively coated treatments, particularly those with AgNPs at concentrations ≥ 3%, demonstrated robust antimicrobial activity by preventing bacterial and mold growth during 5 days.