Resumen de Raman spectra of thermally excited Brazil nut oil and experimental and theoretical correlation of oleic acid (8 pages)
Q.S. Martins, A.F. Sonsin, L.G.F. Silva, A. Ribas, D.L.L. Oliveira, R.C.S Lima
In this study, Raman spectra of Brazil nut oil were collected through a frying process at temperatures ranging from 50◦C to 250◦C, and of oleic acid at room temperature to compare their respective vibrational bands.The theoretical and scaled Raman frequencies of oleic acid structure were obtained with Density Functional Theory (DFT), using the ccpVDZ, 631G, 6-311G+(d,p) basis set and B3LYP and CAMB3LYP functionals. Experimental results reveal subtle changes in the spectra of Brazil nut oil from 210◦C onwards, characterized mainly by a decrease in the Raman signal and broadening of certain bands, such as those observed at 1746 cm^(−1), 2726 cm^(−1) and 3012 cm^(−1). At temperatures around 230◦C to 250◦C Brazil nut oil undergoes advanced thermal degradation. The linear fit data demonstrate a linear relationship between the Raman signal and temperature increase, with R^(2) values of 0.999 and 0.977, for some bands. The DFT method proved to be useful in predicting oleic acid spectra and vibrational signatures were assigned with the help of the VEDA program. This work highlights the potential of Raman spectroscopy to detect changes in Brazil nut oil during frying.
