Thermal aging of edible oils: spectrophotometric study

Abstract

The aim of the present study was to determine the spectrophotometric and thermal aging properties of various edible oils (olive, peanut, rapeseed, soybean and sunflower oils) which are commonly available in the Czech market. The samples were measured by UV/VIS absorption spectrometry and fluorescence spectroscopy. Detected substances of UV/VIS spectra were compared to expected oil composition; the highest absorbance values were detected in a wavelength range 300-550 nm which can be related to the presence of unsaturated fatty acids. The mixtures of oils were characterized by fluorescence spectroscopy; the individual oils were successfully distinguished according to their excitation-emission profiles. This method was also used to detect the samples of adulterated oils, i.e., the adulteration of high-quality oils with soybean oil. From a physicochemical point of view, the influence of temperature on the compounds of extra virgin olive oil was examined by thermal stress simulation. This thermal aging analysis demonstrated that the amount of oxidation products in olive oil increased during the heating whereas the chlorophyll content decreased. The results showed the ability of the techniques used, UV/VIS absorption spectrometry and fluorescence spectroscopy, to characterize the quality and composition of oils, and to distinguish individual oils in blends. UV/VIS spectrometry was also successfully employed for the evaluation of olive oil qualitative parameters according to the standard quality parameters by the "International Olive Council" (EEC 702/2007).

Proximate Composition, Physicochemical, and Lipids Profiling and Elemental Profiling of Rapeseed (Brassica napus L.) and Sunflower (Helianthus annuus L.) Grown in Morocco

“…The quality of oils can be assessed based on the content of specific substances such as chlorophylls and carotenoids that influence the stability of oils [ 81 ]. Indeed, pigments play an important role in the oxidative stability of oils due to their antioxidant activity; they prevent the autooxidation of vegetable oils [ 82 ].…”

Valorization of spent coffee ground as a natural antioxidant and its use for sunflower oil shelf‐life extension

“…Besides other factors, vegetable oil quality is determined by the content of pigments (chlorophylls and carotenoids) that, due to their high antioxidant activity, influence oils’ oxidative stability preventing autooxidation. [ 49 ]…”

“…Besides other factors, vegetable oil quality is determined by the content of pigments (chlorophylls and carotenoids) that, due to their high antioxidant activity, influence oils' oxidative stability preventing autooxidation. [49] Figure 2E depicts the evolution of chlorophylls' content, throughout the storage period, in the negative control and oils enriched with SCGE or VE at three concentrations (0.01%, 0.02%, and 0.03%). As can be seen in the figure, after the enrichment with antioxidants (SCG or VE), little variations in chlorophylls content were observed.…”

Fatty acid profile and physicochemical, optical and thermal characteristics of Campomanesia adamantium (Cambess.) O. Berg seed oil

“…The absorption at 236 nm may be attributed to different compounds present in the vegetable oil, such as phytocholesterols (phytostanols and phytosterols), tocopherol and others (Gonçalves et al, 2018;Jolayemi et al, 2018). The absorption band at 293 can be attributable to tocopherols and FAs (palmitic, oleic, linoleic and stearic acids) (Lapčikova et al, 2018). Intake of oils rich in phytocholesterols and tocopherols are related with prevention of the cardiovascular diseases, diabetes, obesity, and others (Ogbe et al, 2015;Shahidi & Camargo, 2016).…”