Influence of the atmosphere on the decomposition of vegetable oils: study of the profiles of FTIR spectra and evolution of gaseous products

The thermal stability of vegetable oils may be one of important properties in their use in the food industry, cosmetics and agro-industry, especially for high-temperature applications and there are several methods available to evaluate its thermal stability. In order to investigate the thermal behavior of vegetable oils extracted from seeds of Bixa orellana L., of Caryodendron orinocense K., of Moringa oleifera L., of Chenopodium quinoa W., of Coffea robusta L., of Syzygium cumini and oil extracted from leaves and flowers of M. oleifera L., the following analyzes were performed: FTIR, thermogravimetric study and analysis of gases evolved in thermal decomposition. The spectra obtained through the FTIR showed that all oils have similar characteristics, changing the peak intensity between the samples, which can be used to characterize a sample lot, since the composition can vary from lot to lot. It can be observed that the atmosphere of thermal decomposition influences the profiles of the TG and DTG curves. The samples when submitted to the atmosphere of synthetic air exhibited three mass losses while in atmosphere of N-2 they exhibited a single stage of decomposition. The FTIR spectra of the decomposition products of the vegetable oils obtained in the atmosphere of synthetic air and nitrogen are useful data for the characterization of vegetable oils. In relation to the evolution profiles of the decomposition products, in synthetic air and nitrogen, the intensity and the profile of the temperature absorbance plot are related to the composition of each sample.