Desenvolvimento de filmes finos de isolado protéico de soja, taninos e lignina kraft obtidos pelo método de casting

Abstract

The development of active biodegradable thin films has gained extreme relevance due to its potential for application in materials from the food packaging sectors and also due to issues of sustainability and environmental protection. The work aims to prepare sustainable bioplastics from soy protein isolate (SPI) incorporated with kraft lignin and barbatimão tannins (Stryphnodendron adstringens) for use as food packaging with antioxidant potential. The films were prepared by applying two techniques of film-forming (at three different pH's of 8.5, 9.5, 10.5), one of blends and the other of polymeric composites, with different concentrations of lignin and tannins in the IPS matrix using the casting method, an emerging technique for producing biopolymeric films. The films were characterized in physical-chemical parameters with Fourier Transform Infrared Spectroscopy by Reflectance (FTIR), Water Vapor Permeability (PVA), Contact Angle (CTA), Free Surface Energy (SEN), Wettability (WTB) and Determination of Antioxidant Activity (DPPH), mechanical with uniaxial Traction and Drilling tests, thermal with Thermogravimetric (TGA), Differential Scanning Calorimetry (DSC) and in the morphological parameter using Scanning Electron Microscopy (SEM), in order to ascertain the homogenization of the samples and whether the degree of reinforcement addition interferes with their properties. The results showed that the methodology used in the formation of composites presented the best results in the characterizations of SEM, CTA, DPPH and PVA. In mechanical tests the composites showed significant prominence, compared to the control film and the treatment of blends, resulting in a gradual decrease in the elasticity module and tensile strength while increasing the elongation at break. In the ENS test, composite films showed a higher degree of hydrophobicity when compared to blends and control films, respectively. However, when comparing the thermal and chemical tests (DSC, FTIR, TGA) they did not obtain evidence of significant differences between the samples. Also emphasizing that the different pH's did not considerably influence the interaction forces of the medium, but it provides better results in the potential closer to the basics. The results of this work showed the potential of the casting method for the production of SPI biopolymers incorporated with tannins and kraft lignin, leading, therefore, to the development of multifunctional materials an alternative for sustainable food packaging.