Morphology and functional properties of gelatin-based films modified by UV radiation and bacterial cellulose nanofibers

In the present study, the properties of biodegradable gelatin-based films were modified by UV treatment and the incorporation of 1% (w/w) of bacterial cellulose (BC) nanofibers. UVC light was applied at different exposure times (0, 0.5, 1, and 2 h) into the film-forming solutions. In order to evaluate the synergistic effects of these two treatments, the optimal UV condition was also applied to BC-reinforced solutions. Films were characterized by their physicochemical, mechanical, barrier, optical, thermal, and morphological properties. Results showed that the UV treatment applied for 2 h significantly reduced the water solubility (WS) but did not affect the water vapor permeability (WVP). On the other hand, the incorporation of BC reduced WS and WVP values by 15% and 43%, respectively. Regarding mechanical properties, both treatments significantly reduced film elongation at break. However, the tensile strength (TS) and Young's modulus (YM) were only affected by UV treatment. For the film exposed to the longest treatment time, TS increased from 1.56 MPa (control) to 2.85 MPa, and YM increased from 4.36 MPa (control) to 9.23 MPa. Overall, SEM results showed that all samples had a uniform surface and a cohesive matrix. However, BC-reinforced films showed some additional clusters, which significantly increased opacity values. Regardless of their composition, all gelatin-based films lost their integrity after a 12-day soil burial experiment. Film thickness, moisture content, and color parameters were not affected by any treatment. Furthermore, no synergistic effects were detected.Practical applicationsBiopolymer films and coatings are promising systems to ensure shelf life, quality, and food safety, representing a sustainable alternative to replace traditional petroleum-based materials. Although these films have advantages, mainly due to their biodegradability, their properties are not competitive at an industrial level and need to be improved. Therefore, several studies have investigated the application of physical treatments and new process methodologies to overcome these limitations. The present study evaluated the potential use of UV radiation and bacterial cellulose nanofibers in the development of gelatin-based films. Overall, the results showed that these methods are capable of modifying the properties and structure of films, thus offering an alternative to conventional methods of film production. Mastering the use of advanced technologies for film development could be the key to tailoring biopolymer films and coatings for specific industrial applications.