UV Blocking and Oxygen Barrier Coatings Based on Polyvinyl Alcohol and Zinc Oxide Nanoparticles for Packaging Applications

Abstract

Photodegradation and oxidation are major causes of the deterioration of food, resulting in darkening, off-flavors, and nutrient deficiency. To reduce this problem, novel functional polymeric materials are being developed to retain food’s light sensitivity. Nanofillers are also used in a polymeric film to produce effective UV blockings and oxygen barrier coatings so that the degradation of the food can be delayed, thereby increasing the shelf life. For this purpose, polyvinyl alcohol coatings were prepared by the incorporation of ZnO nanoparticles. Polyvinyl alcohol is a naturally excellent barrier against oxygen, and the addition of ZnO particles at the nanoscale size has demonstrated effective UV blocking capabilities. In this work, the hydrothermal technique is used to produce ZnO nanoparticles, and these produced particles are then incorporated into the polyvinyl alcohol to produce thin films. These films are characterized in terms of the compositional, macroscopic, microscopic, and optical properties via X-ray diffraction (XRD), FTIR, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), as well as UV–VIS spectroscopy. ZnO nanoparticles at different concentrations were incorporated into the PVA solution, and the films were processed via the blade coating method. With the addition of ZnO, the oxygen transmission rate (OTR) of pure PVA was not altered and remained stable, and the lowest OTR was recorded as 0.65 cm3/m2·day·bar. Furthermore, the addition of ZnO increased the water contact angle (WCA) of PVA, and the highest WCA was recorded to be around more than 70°. Due to this, water permeability decreased. Additionally, PVA/ZnO films were highly flexible and bendable and maintained the OTR even after going through bending cycles of 20K. Furthermore, the addition of ZnO showed a significant UV blocking effect and blocked the rays below a wavelength of 380 nm. Finally, the optimized films were used for packaging applications, and it was observed that the packaged apple remained fresh and unoxidized for a longer period as compared with the piece of apple without packaging. Thus, based on these results, the PVA/ZnO films are ideally suited for packaging purposes and can effectively enhance the shelf life of food.

Sustainable and Eco-Friendly Packaging Films Based on Poly (Vinyl Alcohol) and Glass Flakes

“…With the addition of glass flakes, there was a modest increase in transmittance, which was attributable to a decrease in the reflectance of the pure PVA [ 32 ]. The addition of the glass flakes did not decrease the transparency since the refractive index of the PVA and the refractive index of the glass flakes matched perfectly with each other, i.e., 1.48 for PVA and 1.54 for the glass flakes [ 33 , 34 , 35 , 36 ]. Furthermore, when the filler quantity was increased, the transmittance of the layers decreased linearly [ 37 ].…”

“…This loss of transmittance can be attributable either to the light’s scattering caused by micronized glass flakes inside the film, or to any internal defect. The latter appears to be the most apparent possibility, given the transmittance fell linearly as the filler material increased [ 34 , 38 ]. These obtained results clearly demonstrate that the films were perfectly transparent and can be utilized as transparent food packaging for the encapsulation of dried fruits and bakery items.…”

“…Figure 4 clearly shows that increasing the amount of the glass flakes decreased the flexibility, as the initial WVTR of the bent films deteriorated. Figure 4 depicts a comparison of the bending performance of the films [ 34 ]. The pristine PVA films retained their initial WVTR values after 20 K bending cycles.…”

“…Thwing-Albert Instrument Company (West Berlin, NJ, USA) supplied an ASTM E-96-compliant standard aluminum cup with a diameter of 6.35 cm. The experiment was carried out in accordance with the approach described by Channa et al [ 34 ].…”

Psyllium-Husk-Assisted Synthesis of ZnO Microstructures with Improved Photocatalytic Properties for the Degradation of Methylene Blue (MB)

“…It is universally significant not only for the living beings, but also for various domestic activities such as cooking [ 2 ] and washing [ 3 ] and, consequently, it is essential for industrial activities. Besides the agricultural sector, water is consumed in the food [ 4 ], beverage [ 5 ], tanning [ 6 ], paper [ 7 ], chemical [ 8 ], and textile [ 9 ] industries, and so on. The textile industry is huge consumer of water, but these industries produce a huge amount of wastewater [ 10 ].…”