Blends of Chitosan and Water Kefir Grain Biomass Incorporated with Nanosilica

The use of by-products from the food industry for the development of bioplastics represents an outstanding strategy in meeting current demands for material circularity. In this work, films based on chitosan (CH) and water kefir grain (WKG) biomass incorporated with different concentrations (3%–10% w/w) of nanosilica (SiO2) were developed for the first time. The key properties required for food packaging were assessed. There are no structural changes (FT-IR) upon nanosilica incorporation. However, the XRD analysis indicates a tendency toward an increase in the amorphous character of the films. For the films with higher proportions of nanosilica, the SEM images indicate particle agglomeration points. The control film (CH/WKG) experienced a 5% mass loss at 68.3 °C, while the CH/WKG10%SiO2 film showed the same mass reduction at 75.7 °C, indicating the nanoparticles increased the moisture-associated thermal stability of the films. The tensile strength was not significantly influenced by the incorporation of nanosilica, but there was an increase in elongation at break, from 25.01 ± 3.67% (CH/WKG) to 40.72 ± 4.89% (CH/WKG/3%SiO2), followed by a drastic reduction to 9.10 ± 1.99% (CH/WKG/10%SiO2). Overall, 3% of SiO2 may be the most promising concentration for CH/WKG blends in future application as sustainable alternatives for food packaging, since it is possible to improve properties, such as ductility and thermal stability, at this concentration without marked losses in the tensile strength of the films