Use of Zinc Oxide Nanoparticles Incorporated in Polybutylene Adipate Terephthalate for Food Packaging. A Focus on the Impact in Functional and Physic‐Mechanical Properties and on Migration Thereof

Abstract

Polybutylene adipate terephthalate (PBAT) and zinc oxide nanoparticles (ZnO NP) are among the most studied when it comes to address biodegradability and antimicrobial properties of materials for food packaging. This work presents a critical review of recent scientific literature with a focus on the impact in functional, physic‐mechanical properties, compostability and on safety. The properties of the nanoparticles, such as morphology and size reported are reviewed together with the range of concentrations and methods of incorporation in the PBAT matrix. The effect on antimicrobial and antioxidant activities, thermostability, tensile and optical properties, as well as on mass transfer properties (barrier to moisture and gases and migration into foods) is discussed. The properties of PBAT/ZnO depend on particle size, shape and concentration of the ZnO NP. Particles with higher surface area and smallest size are reported to have the best performance (usually the spherical shaped). However, information on the morphology/size of the nanoparticle is often not provided. The typical concentration of NP incorporation ranges from 0.5 to 5%, but the interpretation of results regarding the effect of concentration is highly limited due to poor information on the statistical significance of the results, particularly for low concentrations of incorporation. Another limitation found regards the film production method, because most of the studies are based in films prepared by solvent‐casting and not by extrusion. Antimicrobial activity is directly linked with the concentration of ZnO NP. Most studies applied in vitro experiments and not tests in real foods (in situ). Zinc migration can occur as the whole nanoparticle or in the ionic form. Studies indicate that migration of ZnO in the nano form is not expected if the nanoparticle is completely embedded in a polymeric matrix, which can be confirmed by some well‐established techniques. However, studies focusing on migration from other matrices are lacking. Further investigations are needed to achieve a balanced incorporation of ZnO NP considering the particle activity and zinc migration and to evaluate the impact on safety when used in food packaging.