Estudo da mucilagem de Abelmoschus esculentus (L.) Moench (quiabo) e suas potencialidades na composição de filmes biodegradáveis

Abstract

The presente work has as the main objetive identify and analyse the polysaccharide that constitute the okra (Abelmoschus esculentus (L.) Moench) through some chemical and physicochemical characterizations, in order to provides informations and ground your utilization in biodegradable films. Therefore, the okra mucilage was extracted in aqueous neutral solution and it was precipitated with ethyl alcohol. Then, the precipitate was macerated until presents pulverized form and submitted to analyzes. Analyzes of Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy (SEM/EDS) and Fourier-Transform Infrared Spectroscopy (FT-IR) were performed. The SEM provided some microstructural information of the granules, which presented some similarity with those of other pectins present in the literature. The TGA analysis in conjunction with DTG revealed three stages of mass loss, where the first step of loss is relationed with the evaporation of volatile solvents and water (30-150 °C), the second stage is relationed with the degradation of pectin by pyrolytic decomposition (200-730 °C) and the third step (from 735 °C) is relationed with the oxidative process. The DSC curve obtained showed an endothermic peak at 180 °C and another at 290 °C, being the first stage attributed to water loss and the second to the degradation stage, confirmed by the TGA. Two endothermic peaks at temperatures of 128 °C and 140 °C, not shown in the literature, can be attributed to decomposition reaction processes or loss of poorly adsorbed water. SEM/EDS analysis showed certain mineral salt ions, such as calcium (Ca2+) and potassium (K+), besides indicating the presence of some other non-commonly analyzed ions such as aluminum (Al3+), arsenic (As3+) and silicon (Si4+). The spectra obtained by FT-IR showed some characteristic bands of the studied material, exhibiting some similarity with the commercial pectin spectra. There were shown bounded O-H stretches (3800 – 2500 cm-1), C-H stretches (3000 - 2900 cm-1), C-O stretches (1050 cm-1: alcohols, esters, ethers or carboxylic acid) and stretches C=O of the COO- group at 1650 cm-1. The analysis did not show the band corresponding to the C=O of esters and nor of carboxylic acids. The high degradation temperature and the resistance to the oxidation process showed by the analyses are some of the factors that may contribute to the improvement of the properties of biodegradable films.