ABSTRACT
There are a diversity and variability of oil producing plants and different extraction methods. These vegetable and essential oils are substances stored and released by plants from their fruits, leaves, flowers, bark and stem, being complete of plant origin that provides some benefits. In the plant these oils are also known as antioxidant substances, which have the function of natural protection. It is known that the extraction method has a strong influence on its quality and composition due to its variability and environmental conditions, besides possible adulteration. Oils that are rich in polyunsaturated fatty acids are the most relevant to the cosmetic industry but are most sensitive to oxidation. The oxidation of these oils generates what is known as rancidity, with the presence of smaller and undesirable molecules, thus reducing the quality of the oil beyond its nutritional value, making them harmful to human health. Stocking conditions, such as exposure to sunlight and heat, are major phenomena that accelerate the degradation of these oils. Infrared spectrometry with Fourier transform (FTIR) is a tool with potential to evaluate the degradation effect of vegetable oils. Infrared spectra of Almond (Prunus dulcis), Andiroba (Carapa guianensis aubl.), Copaíba (Copaifera langsdorffi) and Rosehip (Rosa aff. Rubiginosa) oils before and after exposure to sun light for 90 days were analyzed, with objective of evaluating the effect of the degradation on the composition of the oil, which were acquired in local commerce of the city Porto Velho. The spectra trends show the occurrence of oxidation, with the reduction of unsaturation, in addition to the fractionation of carbon chains and appearance of functional groups such as aldehyde and alcohol.