Preparation and characterization of cinnamaldehyde/polyvinyl alcohol/silver nanoparticles ternary composite films

Application of Ag@SiO2 nanoparticles within PVA to reduce growth of E. coli and S. aureus in beef patties

To overcome defects of polyvinyl alcohol (PVA) and expand its applications in food preservation, PVA/Ag@SiO₂ nanocomposite films were prepared using the solution intercalation film-casting method. Transmission electron microscopy, X-ray diffraction, and UV-visible absorption spectra were applied to confirm the synthesis of the nanoparticles (NPs). Effects of Ag@SiO₂ NPs on physicochemical characteristics of films like viscosity, swelling ratio, tensile strength, elongation at break, as well as antibacterial activity were also evaluated. Results indicate that Ag@SiO₂ NPs could be synthesized successfully, and the increasing concentration of Ag@SiO₂ NPs led to the decrease in viscosity and the swelling ratio of the PVA/Ag@SiO₂ NPs nanocomposite films. PVA/Ag@SiO₂ nanocomposite films exhibited increased tensile strength and strong antibacterial activity against Escherichia coli and Staphylococcus aureus. The films had higher antibacterial activity toward E. coli compared with S. aureus. Beef patties were applied to verify the practicality of PVA/Ag@SiO₂ films. PVA/Ag@SiO₂ NPs nanocomposite films act as an active food packaging system showing great potential in retaining food safety and prolonging the shelf-life of packaged foods. PRACTICAL APPLICATION: During the storage of fresh meat, the microbial count on the meat surface increased with increasing storage time; meat proteins could be broken down by microorganisms, causing the tissue structure to be destroyed, leading to loose muscle fibers and loss of nutrient-containing juices. In this paper, by improving the PVA film, a new antibacterial membrane was prepared, which can be used for fresh meat sold in supermarkets, as a lining at the bottom of the meat or directly covering the meat. The method can significantly decrease the number of microorganisms and extend the shelf-life of fresh meat.

Synthesis of Sodium Alginate-Silver Nanocomposites Using Plasma Activated Water and Cold Atmospheric Plasma Treatment

In this study, sodium alginate (SA)-based, eco-friendly nanocomposites films were synthesized for potential food packaging applications using silver nitrate (AgNO₃) as the metal precursor, reactive nitrogen and oxygen species (RNOS) created within plasma activated water (PAW), or through cold plasma treatment (CP) as reducing agent and SA as stabilizing agent. The formation of silver nanoparticles (AgNPs) was confirmed via the absorption peaks observed between 440 and 450 nm in UV-vis spectroscopy. The tensile strength (TS) and tensile modulus (TM) of the nanocomposite films were significantly higher than those of the SA films. An increase in the TS was also observed as the AgNP concentration was increased from 1 to 5 mM. The storage modulus (G’) of the nanocomposite solution was higher than that of the SA solution. The synthesis of AgNPs resulted both in a higher solution viscosity and a more marked shear-thinning effect. The synthesized AgNPs showed antimicrobial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The AgNPs were spherical in shape with an average size of 22 nm.