Uso da lignina de coproduto do pedúnculo do caju como ativo de filmes à base de amido de milho com propriedade de bloqueio da radiação UV

Abstract

Ultraviolet (UV) radiation can accelerate oxidative processes in foods, compromising their sensory and nutritional characteristics. As a strategy to minimize these effects, packaging materials with UV-blocking capacity, as well as active packaging capable of scavenging free radicals, have been increasingly developed. In this context, biodegradable and low-cost biopolymers, such as lignin, have attracted growing attention. This study aimed to develop and characterize corn starch-based biofilms incorporated with lignin extracted from residues of cashew peduncle processing, aiming at their potential application in active food packaging. Films containing 1, 3, and 5% (w/w) lignin were prepared using the casting method and evaluated for rheology, mechanical properties, color, hydrophobicity, UV-blockin/g properties, antioxidant activity, biodegradability, and recyclability. The film-forming solutions exhibited non-Newtonian pseudoplastic rheological behavior (n < 1), with viscosity decreasing as shear rate increased, and the data were adequately described by the Power Law model. The presence of lignin promoted changes in the structural properties of the films, with a reduction in tensile strength (from 13.89 to 6.32 MPa) and an increase in elongation at break (from 29.04 to up to 57%), indicating greater flexibility and deformability of the polymer matrix as lignin concentration increased. Progressive darkening of the films was also observed, with a reduction in lightness (L*) and an increase in reddish and yellowish tones. Furthermore, lignin addition significantly increased the hydrophobicity of the films, reducing water absorption from 86.32% (control) to 68.64% (3% lignin) and increasing the contact angle from 68.62° to 77°. Sorption isotherms showed type III behavior and were satisfactorily fitted by the GAB and Peleg models at 25 and 35 °C. Films containing 3% and 5% lignin completely blocked UV radiation, while antioxidant activity increased proportionally with lignin content. Biodegradation ranged from 33% to 46% after 35 days, and films containing 1% and 3% lignin showed effective recyclability, maintaining their antioxidant and UV-blocking properties after reprocessing. These results demonstrate that lignin derived from cashew peduncle residues is a promising sustainable component for the development of multifunctional active packaging materials, with strong potential to protect foods against photo-oxidative degradation and contribute to extending shelf life.