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Postharvest diseases caused by fungi are reported as one of the main causes of food loss, mainly in the fruit and vegetable (FV) sector. Antimicrobials, such as zinc oxide nanoparticles (ZnOnano) and sodium benzoate (SB), have shown good results as postharvest technology for the FV sector, increasing the food shelf life and reducing losses. This work aimed to develop and characterize films made from sodium alginate and chitosan composites, incorporated with ZnOnano or SB to be used as postharvest fruit packaging. To develop the composite film-forming solutions of alginate (2% m/v) and chitosan (1% m/v) were prepared and mixed in a 9:1 ratio (alginate/chitosan). The alginate crosslinking process was carried out before mixing by crosslinking the polymer with calcium chloride at two different concentrations (0.375% or 0.5%). ZnOnano < 50 nm (0.5 mg/mL) or SB (30 mg/L) were added to the filmogenic solution, plated into Petri dishes, and dried in air circulation oven at 40°C/16 h. The different films obtained were analyzed for their visual appearance, color, opacity, thickness, mechanical properties, humidity, and solubility in water. The statistical analysis was performed by two-way ANOVA, Tukey, and Scott-Knott with 5% of significance. The studied polymeric composition provided plastic and flexible films, with a homogeneous visual appearance regardless of the crosslinking agent concentration or the addition of different antimicrobials. The films added with ZnOnano presented more cohesive appearance than the other films and all of them presented a yellowish color tone, provided by the higher alginate proportion used in the formulation, where the parameter b*, which measures the variation between shades of blue and yellow, showed positive values between 9.31 ± 0.789 and 11.5 ± 3.37. The films showed high transparency, confirmed by the values of low opacity600 nm, lying between 0.99 ± 0,08 and 2.35 ± 1,03. The crosslinking process and the addition of ZnOnano could change the film's physical properties, leaving them with less thickness, higher rupture tension, lower elongation at break, and higher Young's modulus, when compared to non-crosslinked films and without the addition of antimicrobials. The average moisture content of films with lower crosslinking (18.7 ± 1.241%) was higher when compared to the average of films with higher crosslinking (17.11 ± 0.586%). The films incorporated by different antimicrobial agents also showed significant moisture averages when compared to films without them. The addition of antimicrobial agents probably increased the hygroscopicity of the films, and the cross-linking agent concentration did not influence this variable. All films were highly soluble in water (54.9 ± 3.55 - 80.9 ± 11.4%) after 24h indicating that the crosslinking process and the change in the film's structure with ZnOnano, were not enough to make them less soluble. Despite the structural change that occurred in the films with crosslinking and the addition of ZnOnano, new experiments need to be performed, increasing the concentration of the crosslinking agent to reduce the solubility of the films and enable their use as food packaging.

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  • 1 Universidade Federal do Estado do Rio de Janeiro
  • 2 Universidade Federal Rural do Rio de Janeiro
  • 3 Empresa Brasileira de Pesquisa Agropecuária
  • Colloids for edible films
NANOPARTICLES; biocomposite; Postharvest