Squalene is a triterpene, and tyrosol is a simple phenol. Both are found in relatively high amounts compared to other terpenes and phenols respectively in extra virgin olive oil, and are reduced significantly during refining to produce refined olive oil. Both squalene and tyrosol can be determined by hplc (high performance liquid chromatography) after extraction with 2-propanol or liquid-liquid extraction respectively. The feasability of this screening method was first tested on measuring the two markers in 10 commercial samples of EVOO, one commercial sample of virgin olive oil, 2 commercial samples of olive oil (a blend of extra virgin and refined olive oil), and 10 types of vegetable oils. In addition, the method was tested on 6 brands of blended oils (5 of which were 20% EVOO/80% sunflower oil, and one 30% EVOO/70% grapeseed oil). Further samples of olive oil using 50% EVOO, and blended oils with 20% EVOO were prepared. After determining squalene and tyrosol in all of the samples and plotting squaline on the y-axis, and tyrosol on th x-axis, there was discrimination between EVOO and all the other samples, and olive oil samples were differentiated from blended oils. Although this showed feasibility of the screening method, more samples at different concentrations of EVOO, and of virgin olive oil are required to find the sensitivity of the method.
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