Food packaging materials such as glass, paper, and plastics are used to preserve and lengthen the shelf life of food products. Among the materials, plastics are widely used due to their excellent properties. However, conventional plastics are usually made up of petroleum resources that are non-sustainable and non-degradable, thus increasing the municipal solid waste in the landfill which can lead to serious pollution. As an alternative, biopolymer materials such as starch have great potential to replace conventional plastics due to their non-toxicity, non-pollutant, biodegradability, edibility, and availability.
However, the mechanical, thermal, and barrier properties of the biopolymer materials are not comparable to conventional plastics which limit their application as food packaging materials. The advancement of nanotechnology reveals that the incorporation of nano-sized materials as fillers such as chitosan nanoparticles (CNP) into the matrix of the starch biopolymer to produce bionanocomposite is effective to improve the properties of biopolymers compared to bulk material counterparts. The minuscule size of the fillers leads to the extreme increment in the surface area of the fillers which is favored for bionanocomposites for a large interfacial area between the biopolymer matrix and filler. The large interface allowed the modification of molecular mobility and relaxation behavior, thus improving the properties of the bionanocomposite materials. The CNP incorporated in the composites also exhibits active roles such as antimicrobial and antioxidant agents that can extend shelf life and maintain the quality of foods, thus ensuring food safety and security.
When the optimum concentration of CNP is incorporated into starch biopolymer to produce starch/CNP bionanocomposite, the bionanocomposite material is found to exhibit high transparency which is desirable for food packaging applications. The tensile strength and the elongation at break of the material are improved by 7.96 and 0.35-fold increments, respectively due to the formation of strong intermolecular hydrogen bonding between the starch chain and CNP. The mechanical properties of the material are comparable to commercial food packaging plastic particularly low-density polyethylene (LDPE). The thermal stability of the material is also improved by a 2-fold increment. The barrier properties in terms of water vapor and oxygen permeabilities are improved by 4 and 0.5-fold, respectively due to the formation of a tortuous pathway in the biopolymer matrix with the existence of CNP.
The starch/CNP bionanocomposite also exhibits antibacterial properties when tested against gram-positive (Bacillus cereus, Staphylococcus aureus) and gram-negative (Escherichia coli, Salmonella typhi) bacteria. The starch/CNP bionanocomposite materials manage to maintain the quality and extend the shelf life of food, particularly cherry tomatoes packaged with the material to more than 10 days, demonstrating the potential of the material as food packaging material.
Knowledge from this research is important to the development of sustainable and environmentally friendly food packaging materials that are active and exhibit good properties, thus supporting the National Green Technology Policy. This will meet increasing demands in society and nation for sustainability, environmental safety, and quality as well as contribute to food safety and security.
Assoc. Prof. Dr. Siti Hajar Othman
Nano Materials Processing and Technology Laboratory (NPTL)
Institute of Nanoscience dan Nanotechnology
Date of Input: 02/03/2022 | Updated: 29/03/2022 | roslina_ar
Institute of Nanoscience and Nanotechnology,
Universiti Putra Malaysia,
Selangor Darul Ehsan, Malaysia