Metallic Nanofillers in Food Packaging

Read to find out the types of Nanofillers and the impact of Metallic Nanofillers in Food Packaging.

Parameswari P L, Priyanka, Somveer, Kumari M

In the ever-changing world of food packaging, the search for safer, more sustainable, and longer-lasting solutions is never-ending. One notable advancement in this area is the incorporation of metallic nanofillers into food packaging materials. Polymer nanotechnology was initiated to increase gas barrier performance for gases such as oxygen and carbon dioxide. It has also been shown to improve the barrier performance to UV radiation, as well as to boost strength, stiffness, dimensional stability, heat resistance, and antimicrobial property. Nano-particles having dimensions ranging from 2 to 100 nm are synthesized or machined for their widespread application across various industrial sectors due to their distinctive physical and chemical properties. These properties encompass their size, configuration, surface charge, surface area, surface porosity, composition, structure, propensity for agglomeration, and distribution in terms of particle size (Rezic et al., 2017).

Nano-fillers can be made of cellulose, metals, clay or carbon. Metallic nano fillers can be made from a variety of metals, including  silver, gold, copper, zinc, and titanium. Each metal has its unique set of features and functions. Metallic nano-fillers have an extremely high surface area to volume ratio due to their nano-scale size.

Types of Metallic Nano-fillers

1. Silver nano-particles (Ag NPs): These are commonly used in food packaging due to their antibacterial characteristics. They have the ability to suppress the growth of bacteria, fungus, and other microbes. Thus, Ag NPs can be incorporated as an additional layer of protection against microbial development.
2. Zinc oxide nanoparticles (ZnO NPs): Zinc oxide nanoparticles are well-known for their antibacterial and UV-blocking characteristics. To improve food safety and increase the shelf life of UV-sensitive items, ZnO NPs can be integrated into packaging materials.
3. Copper nanoparticles (Cu NPs): Copper nanoparticles possess excellent antimicrobial properties and have been shown to inhibit the growth of various bacteria and fungi.
4. Gold nanoparticles (Au NPs): They have unique qualities such as high stability, biocompatibility, and low toxicity. While their usage in food packaging is less prevalent than that of other metallic nanofillers, they have been investigated for applications such as active sensing and intelligent packaging due to their optical characteristics and simplicity of functionalization.

Properties of Metallic Nano-fillers

1. Barrier properties: Metallic nano-fillers, such as silver, gold, or zinc oxide nanoparticles, can improve barrier property of package by forming a dense network within the polymer matrix. This lowers gas, moisture, and organic compound permeability and contributes to the extension of food product shelf life and preserve freshness. Sanuja et al. (2015) investigated the water vapour permeability of chitosan films incorporated with three different concentrations of zinc oxide nanoparticles (0.1%, 0.3%, and 0.5%), and discovered that increasing the nanoparticle concentration in the formulation decreased the material’s water vapour permeability.
2. Antimicrobial properties: Metallic nanoparticles, particularly silver nanoparticles, possess antimicrobial properties. Incorporating metallic nano-fillers into food packaging materials can help reduce the risk of microbial growth and enhance food safety. Shankar et al., (2018) reported that regenerated cellulose/metallic NPs hybrids showed strong antibacterial activity against coli and L. monocytogenes.
3. UV blocking: Some metallic nano-fillers, such as titanium dioxide nano-particles, offer exceptional UV-blocking properties. They can absorb or deflect UV light, protecting food from UV-induced damage, colour fading, and nutritional loss. This characteristic is especially advantageous for light-sensitive foods.
4. Antioxidant properties: Antioxidant characteristics are exhibited by as selenium or zinc nano-particles. They can scavenge free radicals and limit oxidation events, thereby preserving the nutritional value and quality of packaged foods.
5. Mechanical reinforcement: Incorporation of metallic nano-fillers can improve the stiffness, strength, and tear resistance of the packaging, offering superior protection for the food goods during handling, transportation, and storage. Siripatrawan and Kaeweklin (2018) tested the mechanical properties of chitosan films reinforced with four different concentrations of TiO2 (0.25%, 0.5%, 1%, and 2%). The tensile strength efficacy improved with the addition of nano-particles, with 1% TiO2 achieving the highest significant value.
6. Sensing capabilities: Metallic nano-fillers can be used to detect and monitor food quality characteristics. For example, gold nano-particle based nano sensors can be constructed to detect certain gases, such as ethylene, which is related with the ripening of fruits and vegetables. This permits the creation of smart packaging capable of providing real-time information regarding the freshness and quality of packaged food.
7. Thermal stability: Metallic nano-fillers can improve the thermal stability of packing materials, allowing them to endure high-temperature operations such as sterilisation or microwave heating. They can improve the heat resistance and thermal conductivity of the packaging, preventing deformation or melting during food processing.

Conclusion

Metallic nano-fillers have emerged as a potential and unique approach for improving the quality of food packaging materials. Their distinct characteristics, such as antibacterial, barrier, and mechanical reinforcement, make them an invaluable addition to the food packaging sector. We can increase the shelf life of food products, improve their safety, and reduce food waste by integrating metallic nano-fillers into packaging materials. Furthermore, the usage of metallic nano-fillers in food packaging coincides with the increasing need for environmentally friendly and sustainable packaging solutions. These nano-fillers have the potential to enable the development of thinner and lighter packaging materials, hence lowering the total environmental effect of  packaging manufacturing and disposal.

Reference

Rezić, I., Haramina, T., and Rezić, T. (2017). Metal nanoparticles and carbon nanotubes—perfect antimicrobial nano-fillers in polymer-based food packaging materials. Food packaging, 497-532

Sanuja, S., Agalya, A., and Umapathy, M.J. (2015). Synthesis and characterization of zinc oxide-neem oil-chitosan bionanocomposite for food packaging application. International Journal Biological Macromolecules, 74, 76–84.

Shankar, S., Oun, A. A., and Rhim, J. W. (2018). Preparation of antimicrobial hybrid nano-materials using regenerated cellulose and metallic nanoparticles. International Journal of Biological Macromolecules, 107, 17-27.

Siripatrawan, U., and Kaewklin, P. (2018). Fabrication and characterization of chitosan-titanium dioxide nanocomposite film as ethylene scavenging and antimicrobial active food packaging. Food Hydrocolloids, 84, 125–134.

About the Authors

1 PhD Scholar, Dairy Engineering Division, ICAR-NDRI, Karnal, Haryana, India

2 Scientist, Dairy Engineering Division, ICAR-NDRI, Karnal, Haryana, India

3 Teaching Associate, Division of Dairy Engineering, CoDS&T, RAJUVAS, Bikaner, Rajasthan, India