The Effect of Active Chitosan Films Containing Bacterial Cellulose Nanofiber and ZnO Nanoparticles on the Shelf Life of Loaf Bread

Abstract

Due to the disadvantages of synthetic packaging materials such as migration, environmental pollution, lack of easy recycling, and high production costs, natural polymers have received much attention as safe and biodegradable alternatives to plastics. The aim of this study was to investigate the effect of the active film of chitosan (CH) containing bacterial cellulose nanofiber (BCNF) and ZnO nanoparticles (ZnO NPCs) on the shelf life of loaf bread (toast, baguette, and sandwich-type bread). The results showed that ZnO NPCs significantly reduced the thickness and water vapor permeability (WVP) and increased the opacity of films p < 0.05 . CH-BCNF-ZnO 2% NPCs film had the lowest thickness and WVP and the highest opacity. Differential scanning calorimetric (DSC), thermal gravimetry analysis (TGA), and derivative thermogravimetry (DTG) showed that ZnO NPCs increased the thermal stability of chitosan films. CH-BCNF-ZnO 1% NPCs had the highest melting point (148.66°C) and melting enthalpy (ΔHm). Scanning electron microscopy (SEM) images showed the good distribution of ZnO NPCs in the chitosan film. The higher concentrations of ZnO NPCs formed aggregates in the polymer. ZnO NPCs had a significant effect on the physicochemical properties of bread. The highest moisture content and water activity a w were observed in CH-BCNF-ZnO 2% toast and control toast, respectively. CH toast showed high ash and insoluble ash. CH baguettes and control baguettes showed the highest pH. As the ZnO NPCs concentration increased, the nanoparticle migration increased. The highest migration was observed in CH-BCNF-ZnO 2% baguette. The highest and lowest hardness was observed in CH-BCNF-ZnO NPCs 2% baguette and CH-BCNF- ZnO NPCs 1% toast bread, respectively. Composite films decreased the microbial population in all bread samples except sandwich-type bread. It can be concluded that BCNF and ZnO NPCs improve the physical properties of chitosan film and can be suggested as active packaging in bread.

Impact of polymeric films and hydrogels: Physical characteristics on bacterial growth

“…by the binding of CS and DNA. 85 The other mechanisms demonstrate that CS acts as a chelating agent, which can bind to the metal ion, resulting in toxin production and inhibition of bacterial growth. 86 However, the effect of CS on bacteria had been found to the limited, which depended upon the molecular weight (M w ) of CS.…”

“…In a deep mechanism, CS has penetrated the bacterial cell wall via the properties of the amine group. mRNA synthesis, DNA translation, and bacterial proliferation have been inhibited by the binding of CS and DNA 85 . The other mechanisms demonstrate that CS acts as a chelating agent, which can bind to the metal ion, resulting in toxin production and inhibition of bacterial growth 86 .…”

Agricultural waste as a sustainable source for nanoparticle synthesis and their antimicrobial properties for food preservation

“…Gelatin films have also integrated zinc oxide nanoparticles, positively impacting bread samples by reducing weight loss and decreasing bacterial growth compared to the control, for 9 days of storage (Yasmeen et al, 2023). Bakouei et al (2023) used chitosan films with ZnO nanoparticles, decreasing water vapor permeability, and inhibiting the growth of mold and yeast at a temperature of 25 °C for 60 days (Bakouei et al, 2023).…”