Síntese e caracterização de filmes multifuncionais de isolado proteico com lignina kraft para embalagens

Abstract

Research aimed at producing multifunctional and biodegradable films has gained interest and visibility. In this line, kraft lignin (KL) is a promising additive to add functionalities and increase biopolymers' thermal, mechanical, and hydrophobic performance. Currently, many studies used nanoparticle, chemical modification, and compatibilizer methodologies to improve lignin homogeneity in the hydrophilic matrix. However, such approaches present low performance and demand high energy consumption and reagents. Thus, a more economical and simplified alternative is mixing through the mutual miscibility of the components. Therefore, the objective of the present study was to develop and characterize multifunctional films of Whey Protein Isolate (WPI) with the addition of different concentrations (2, 4, 6, and 8%) of KL dissolved in an alkaline solution. Then, the films formed by casting were characterized by their morphological properties (Scanning Electron Microscopy), chemical (Fourier Transform Infrared Spectroscopy), hydrophobic (Solubility, Water Vapor Permeability (PVA) and Contact Angle), Thermal (Thermogravimetry, Differential Exploratory Calorimetry, and Sealability), Mechanical (Tensile Strength, Elongation to Rupture and Young Module) and Antioxidant and UV-Block functionalities. The addition of solubilized KL produced homogeneous films without agglomerates and with higher hydrophobicity when compared to the control film. In the treatments with 4% lignin (LP4), KL acted as reinforcement by producing films more resistant, but also brittle, which prevented the films' heat-sealing. The samples with 8% (LP8) obtained a higher antioxidant activity (34.69%) and 100% UVA/UVB block, increasing the thermal stability and the Tg of the films. In conclusion, the solubilization of lignin before being added in the IPS solution proved to be an efficient methodology for producing multifunctional films, with potential application for food packaging with high lipid content.