Adição de ácido esteárico e surfactante em filmes elaborados com proteínas miofibrilares obtidas de corvina (micropogonias furnieri).

Abstract

The interest in biodegradable films as food packaging is a worldwide trend that has increased significantly in recent years. The myofibrillar proteins, particularly fish ones, have been gaining interest in film technology. The films made from polysaccharides or proteins have excellent mechanical and optical properties, but these films have a high water vapor permeability (WVP). The incorporation of hydrophobic substances, such as stearic acid, into the film-forming solution, is an alternative to increase the barrier properties of the film to water vapor. But to facilitate the incorporation of the lipid in the protein matrix, it is necessary to add surfactant, which are substances capable of interacting with the protein and the fatty acid. The objective of this work was to develop and characterize films of myofibrillar proteins obtained from corvina waste (Micropogonias furnieri) using glycerol as plasticizer, sodium dodecyl sulfate (SDS) as surfactant and stearic acid (SA) as lipid, to improve the technological properties of the film. The characterization of the waste and lyophilized myofibrillar proteins (MP) was performed, indicating that the raw material had a high protein content (96.03% b.s.), important for the formation of the biopolymer matrix. A complete factorial planning was done to define the region of better mechanical, physical and barrier properties of films. The optimized biofilm was prepared with 2.84% MP, 3.18% SA, and 78.41% SDS and 30% glycerol. Concentrations of SA and SDS significantly reduced the WVP, reaching 5.87E-11 g m m-² s-¹ Pa-¹, representing a reduction of 31% when compared to the control biofilm. The mechanical properties of the optimized biofilm were favored, presenting 235.60% of elongation and 6.35 MPa of tensile strength producing stronger and more flexible films. The values of transparency were high, indicating tendency to opaque and yellowish tone, however, with excellent UV barrier properties and it can be used in light sensitive foods. The optimized film also presented good thermal stability and the microstructure revealed a structural change in the filmogenic matrix, in relation to the control, with presence of grooves and protuberances on the surface, confirmed by X-ray diffraction, which indicated the influence of SDS and SA on crystallinity of the film. A 22% increase in solubility and a slight decrease in the swelling of the optimized film were observed.