Quality Control Of Olive Oil By GC-MS Combined With Chemometrics

Abstract:The olive tree is one of the most important crops in Mediterranean countries. The olive oil has the properties of preventing cardiovascular disease, neurological disorders, different cancers, due to its well-balanced fatty acid composition and natural antioxidants. However, the chemical composition of olive oils is different because of different factors such as cultivar, climate, cultivation condition, harvest yea. Besides, as olive oil is usually much more expensive than other edible oils, its adulteration is generally motivated is order to maximize the profits mixing olive oil with cheaper vegetable oils. Thus, it is important to establish an effective analytical method to make the quality control of the olive oil. In this study, we focused on the fatty acid profile and aimed to analyze the difference of olive oils from different regions, the difference of olive oil with other vegetable oils and some adulterated olive oils.In this thesis, alkaline trans-methylationwas first used to transfer the esterified fatty acids to fatty acid methyl esters. Then, GC-MS with SIM model was used to analyze the fatty acid methyl esters and as a result,22fatty acid methyl esters are identified and quantified. Besides these single fatty acids, other six significant parameters (the ratio of linoleic/linoenic acid, oleic/linoleic acid, total saturated fatty acid (SFA), polyunsaturated fatty acids (PUFA), monounsaturated fatty acid (MUFA), MUFA/PUFA) are also under evaluation.Different chemometric methods were next applied to analyze the characteristics of different oils. The results show that the olive oils in China market are different from the ones that directly obtained in European countries. And the olive oils imported from different countries also have different fatty acid composition. These differences are mainly due to the content of saturated fatty acid, which may result from some natural factors. Among the other vegetable oils, the fatty acid composition of tea oils is the most similar with that of olive oils. However, other vegetable oils (corn, peanut, sunflower, rapeseed, sesame oils) have a lower content of monounsaturated fatty acid while higher level of polyunsaturated fatty acids. Besides, the rapeseed oil has a high content of erucic acid, nervonic acid and y-linolenic acid, peanut oil has high content of eicosanoic acid, docosanoic acid, tetracosanoic acid and saturated fatty acids.Based on the characteristics of fatty acid profile, PLS-LDA can effectively detect the adulterated olive oil with1%detection limit and90%prediction ability. Monte Carlo Tree can identify the type of adulteration with85%prediction ability.