Desenvolvimento de filmes à base de goma de cajueiro modificada e goma kappa com reforço de nanocelulose

Abstract

Cashew gum (CG) has been exploited as a matrix for food films, but due to its hydrophilic characteristics, it presents low barrier properties that limit its application. Alternatives such as chemical modification, use of nanotechnology and addition of other polysaccharides to the blends formulation, allow to check improvements in physical, barrier and mechanical characteristics in filmogenic matrices. In this sense, the objective of this work was to modify GC with sodium trimetaphosphate (STMP) and to develop films based on modified cashew gum and kappa gum (KG) added with cellulose nanocomposite (CN). In general, the incorporation of NC and STMP showed a positive contribution to the water vapor barrier of the films, presenting values ranging from 3.71 to 5.3 g/h.m.Pa. This increase is due to the low hygroscopicity of the cellulose nanocrystals and the crosslinking of the gum. The films obtained in this study varied their solubility from 69.22% to 94.37%, where there was a significant difference (p <0.05) between treatments. These results indicate a good interaction of the CG and STMP chains, facilitated by a good dispersion of the CN in the polymer matrix. For the mechanical properties, the addition of nanoparticle had a positive effect, indicating that higher CN percentages provide films with higher tensile strength, elongation and rupture stress. In relation to the thermal analysis, four stages of mass loss were observed for CG/KG films. The second transition region (composed of two peaks or stages) was observed above the temperature of 200 °C to ± 450 °C. In this region, shoulders were observed on the DTG curve at about 230 °C before the major decomposition peak. The division of the second stage into two (forming shoulders) would be related to the fact that films are composed of more than one polymer matrix, which leads to different degradation behavior. For the FT-IR, the spectra of the nanocomposite films presented some of the main bands from the CG and KG, with changes in the intensity and some displacements, presenting few differences when compared to the pure CG sample, with characteristic peaks in the bands 2927 cm-1, 1637 cm-1 and 1074 cm-1. In the SEM, the films show a rough surface with imperfections, but no cracks, except the sample T4 and T8, which presented cracks in its surface, fact attributed to the concentration of the TMS crosslinking agent. It was observed that the contact angles presented values between 49.08° and 78.88°, suggesting that there was a decrease in the interaction between the water and the hydrophilic sites. In relation to the color parameter, the films had a brightness value between 89 and 91, considered clear, indicating a good transparency. In relation to the parameters a* and b*, they presented positive values for both parameters, indicating that they showed tendency to reddish and yellow, resulting in orange coloration.