Obtenção e caracterização de nanocristais de celulose da vagem de soja e avaliação da sua aplicação em filmes de proteína isolada de soja

Abstract

Proteins are biological molecules with high molecular mass, which can be like natural polymers, capable of producing stabilized three-dimensional amorphous structures, mainly by non-covalent bonds. Among proteins, isolated soy protein (SPI) stands out due to its structural and functional properties that allow the formation of structures with characteristics suitable for their use as packaging. There are technologies that aim to improve the physical properties of biodegradable films, among them, the use of cellulose nanocrystals (CNC). CNCs are crystalline nanoparticles, which can be obtained from the acid hydrolysis of the amorphous region of lignocellulosic materials. An example is the soybean pod, which is a high-occurring agroindustrial residue, which presents a high content of cellulose (> 70%), making it a potential CNC source. From this information, the objective of this work was to analyze the effect of the addition of cellulose nanocrystals (CNC) extracted from soybean pod in order to evaluate its influence on some properties of films made from isolated soybean protein (SPI). Five concentrations of SPI films were prepared: Control (without addition of CNC), SPI + CNC0.3 (containing 0.3% CNC), SPI + CNC0.5 (containing 0.5% CNC), SPI + CNC0.7 (containing 0.7% CNC) and SPI + CNC1.0 (Containing 1.0% CNC). The soybean pod used in obtaining the CNC was characterized by the determination of the cellulose, lignin and ash content. As for the CNCs, the yield was evaluated, and they were characterized by dynamic light scattering (DLS) and Zetapuntencial. The films were characterized by X-ray diffractometry (XRD), thickness, water solubility, water vapor permeability (PVA), transmittance and mechanical tensile strength test, maximum stress, strain at break, specific strain and modulus of elasticity. The results obtained by DLS showed that the CNCs have 75nm of size and polydispersity index of 0.645, indicating that the nanoparticles were dispersed homogeneously in aqueous solution. The incorporation of CNC in the SPI matrix caused the decrease of the PVA of the films by 38%, besides provoking the crystallinity increase. The solubility of the films was not altered due to the addition of the CNCs in the formulations