| Abstract: | Twelve sets of olive oil mixed with various edible seed oils in different proportions were made. The seed oils used were sunflower, corn, walnut, rapeseed, soybean, safflower, peanut, wheat germ, and sesame oil. These samples have very different proportions of saturated, mono- and polyunsaturated acyl groups, and of minor components. Fourier transformed infrared spectra of these blends were recorded from films of the oil samples between two discs of KBr. Taking into account the close relationships found previously between the frequency data of some specific bands and the composition of the oil samples, frequency data of all samples were collected and used in equations that relate frequency and composition predicting the percentage by weight of saturated, mono- and polyunsaturated acyl groups in the samples. The predicted values were compared with those derived from the combination of chemical and gas-chromatographic methods and a high degree of agreement was found. The presence of small amounts of seed oil in olive oil is shown by a small variation in the values of the frequencies of specific bands of the spectra, resulting from a smaller proportion of mono-unsaturated acyl groups than in pure olive oil. On the other hand, the frequency of the maximum absorbance between 915 cm–1 and 904 cm–1 also indicates the proportion of seed oil in the blend up to levels of 5% or up to 8% of seed oil in olive oil, depending on the nature of the seed oil. This methodology could give information about the composition of blends of edible oils in a very fast and simple way. |
