Obtenção e caracterização de bionanocompósitos de fécula de mandioca e argila bentonita organofilizada por mistura de tensoativos

Abstract

Biofilms and edible coatings are thin layers of biodegradable materials applied to food products that play an important role in their preservation, distribution and commercialization. Cassava starch is one of the best candidates for the preparation of edible coatings, because it is a completely biodegradable polymer in soil and water and easy to obtain. However, the starch has limitations in its physical-chemical properties when compared to the synthetic polymers. In turn, the improvement of these properties was proposed in this research from the addition of 5%, by mass, of clay in relation to the dry mass of biopolymer. The surface compatibilization of the clay with the biopolymer matrix was performed by surface modification in the presence of three types of surfactants (cetyltrimethyl ammonium bromide, sodium dodecyl sulfate and ethoxylated lauryl alcohol). The effect of three sequential modifications on the clay was characterized by X-ray Diffraction (XRD), Fourier Transform by Infrared Radiation (FTIR), Scanning Electron Microscopy (SEM), Dispersive Lightning Spectroscopy (DLS), Contact Angle (AC), Zeta Potential (ZETA) and Thermogravimetric Analysis (TGA). The clay modified synergistically in the presence of the three surfactants showed the greatest basal space between the silicate layers, about 10 nm more than the natural clay. The cassava starch films with natural and modified clay were characterized as bionanocomposite intercalated or exfoliated through Atomic Force Microscopy (AFM), Optical Microscopy (MO), XRD, FTIR, SEM and AC analyzes. The influence of modified and natural clay on the change in the physical-chemical properties of the original starch films was investigated for water vapor permeability, ductility, opacity, thermal stability and water solubility. Finally, the synergistically modified clay in the presence of the three surfactants was the reinforcing material that contributed the most to the physical-chemical properties of the control starch film, among which it reduced the permeability to water vapor by 90.6%, as well as 77.43% of the maximum dissolution.