Introduction:-
The use of plastic polymers in food packaging causes serious environmental and health problems and as a result, natural biopolymers (NBPs) are being employed in this field. Nanotechnology is revolutionizing the food industry worldwide due to the multiple applications it offers. Nanoencapsulation is the use of nanomaterials and nano sensors in the development of active and/or smart food packaging. In their research, Vincente Amirpasha Tirado-Kulieva and his team at National University Fontera-Sullana have reported the main findings about the effect of integration of metal nanoparticles (MNPs) on the characteristics of NBPs.
Research:-
Food packaging is a dynamic market that exceeded 300 billion dollars in 2019 with an approximate growth of 5.2% per year due to its role in food quality and safety. It’s crucial that food packaging is made of low-cost materials with adequate hardness, flexibility, lightness, strength, and inertness amongst other properties in addition to being easily mouldable. Polyethylene and polypropylene meet the above requirements but these present a high environmental pollution risk.
A solution to the aforementioned problem, lies in the usage of biodegradable products. To provide natural biopolymers with optimal physical, mechanical and barrier characteristics, inorganic and non-toxic nanomaterials are currently being used, in particular metal nanoparticles (MNPs). MNPs are biocompatible, and thus can be incorporated with NBPs to form a hybrid system, an ideal bio-nanocomposite to replace traditional packaging. MNPs enhance the properties of NBPs, contributing to active, novel and efficient packaging. For instance, a glycerol plasticized-pea starch film exhibited poor mechanical and barrier characteristics. However, by incorporating a loading (5%) of ZnO nanoparticles stabilized with carboxymethyl cellulose (CMC), the tensile strength increases by 9.81 MPa, and 42.2% of elongation at break and 11.2 x 10-7 g.m-1.h-1.Pa-1 of WVP were reduced. Moreover, the film had a higher UV-visible absorption. Another advantage of MNPs is that they are used in small concentrations, avoiding modifying the polymeric matrix or causing negative effects on the food quality. MNPs have a broad antimicrobial spectrum. Use of ZnO and CuO nanoparticles inhibit Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and listeria monocytogenes. Superparamagnetic iron oxide and Ag nanoparticles at concentration 25 ppm showed antifungal activity against Fusarium solani and Aspergillus niger. Studies on antiviral effect have also been reported.
The integration of MNPs such as ZnO, Ag and CuO into NBPs (from compounds such as chitosan, CMC and lignin) is performed in small proportions, generally 0.5% to 5%. MNPs significantly increase the antimicrobial activity of NBPs, in addition to improving their antioxidant, physical, mechanical, optical and barrier properties. This generates, in a sustainable way, an active and efficient packaging that improves food quality and prolongs shelf life.
Conclusion:-
Despite the benefits offered by NBP-MNPs, the metal base remains under study due to its potential toxicity, raising concerns and intrigue about its efficacy in the NBPs. Many of the MNPs have been certified as Generally Recognised As Safe (GRAS) by the FDA such as ZnO and TiO2. On the other hand, some MNPs such as Ag can bioaccumulate in the testicles, liver, kidneys and brain. Being a relatively new technique, its application in the food sector is yet to be widely explored.
Reference:-
Kulieva et al., A Critical Review on The Integration of Metal Nanoparticles in Biopolymers: An Alternative for Active and Sustainable Food Packaging, Current Research in Nutrition and Food Science Journal (2022).
By Debangana Banerjee
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