Light Barrier Properties of Flexible Films

Abstract

The development of light barrier films for food packaging has gained more interest in the industry in order to protect food from deterioration and quality loss during the entire production process. Some products are more vulnerable to spoilage when they contain light-sensitive components and/or a high amount of fat. In the presence of light, mainly UV radiation, photochemical reactions generate free radicals that reduce food quality by changes in color and flavor as well as degradation of vitamins, fats and proteins. In addition, these reactions can generate toxic substances which can be harmful to human health. Nowadays, the most commonly used packaging material for light-sensitive food are multilayer flexible films with high oxygen and light barrier. These films often include an aluminum layer which acts as lightblocking material. However, the traditional recycling method cannot be employed for these packaging materials because the adhesives used in multilayer films as well as the combination of multiple materials. Moreover, these films have other drawbacks such as high costs and a non-transparent appearance. Thus, sustainable alternatives are necessary. In this sense, polymer nanocomposites are promising packaging materials due to their better performance as light barrier in comparison with neat polymers. Several types of fillers can be added to the polymeric matrix, including titanium dioxide, zinc oxide, kaolinite and talc which act as light blockers to avoid food spoilage. These particles decrease the light transmittance of films not only as a consequence of their presence, but also by the change they induce in material crystallinity since they act as polymer nucleating agents. Thus, the incorporation of particles is a promising route to improve the light barrier of flexible films. In this chapter, a critical analysis of the state of the art about light barrier films for packaging, mainly those used for light-sensitive food products, is presented. This analysis is focused on different materials for the development of sustainable light barrier flexible packaging.