Chemical profile and adulteration detection of olive oils
Yu, Liangli Lucy
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A combination of ultra-performance convergence chromatography (UPC2) combined with quadrupole time-of-flight mass spectrometry (Q-TOF MS) analyses was utilized to determine the triacylglycerols (TAGs) composition and sn-positions of olive, corn, soybean and sunflower oils, for better understanding of their nutritional value and shelf stability. Ten commercial olive oil samples were analyzed, and a total of 23 TAGs were detected, of which O-O-O was the most abundant TAG in the olive oil samples, followed by P-O-O, O-O-S and O-O-L. The TAGs composition of olive oils were compared to that of the local commercial soybean, corn and sunflower oils. Comparing soybean, corn and sunflower oils with olive oils, L-L-L, P-L-L, B-L-L and M-L-L could be detected in the soybean, corn and sunflower oils but not in the olive oils. Po-O-Po, O-Po-O and G-O-O could be detected only in olive oil and O-O-O was much greater in olive oils. Using UPC2-Q-TOF MS, pure soybean, corn, and sunflower oils could be differentiated from pure olive oil samples based on their triacylglycerol compositions. However, UPC2-Q-TOF MS analysis could not detect olive oils adulterated with small amount of soybean, corn or sunflower oils. UPC2-Q-TOF MS system combined with multivariate data analysis was tested for potential utilization in detecting of olive oil adulterated by soybean, corn or sunflower oils. A combined UPC2-Q-TOF MS and multivariate data analysis approach was developed to potentially detect the olive oil adulterated with other vegetable oils at 0.5% (v/v) level. In addition, 10 representative marker ions of TAGs were selected to create a model using PCA, which could be used to differentiate pure olive oil from the olive oils adulterated with small amounts of soybean, corn and sunflower oils. The UPC2 system coupled with Q-TOF-MS approach can examine TAG sn-position compositions of olive oils with improved resolution of TAGs and reduced use of organic solvent. UPC2-Q-TOF MS may also be a more environmentally friendly approach for the rapid and accurate analysis of TAGs composition in edible oils and fats, as well as biologically lipids. UPC2-Q-TOF MS system combined with multivariate data analyses may be a possible approach for edible oil adulteration detection.