Abstract
Minor compounds in vegetable oils are distributed between free and esterified forms, and the ratio of these two fractions could represent an important parameter for assessment of oil authenticity. A simple method based on offline SPE-GC-FID for the analysis of free and esterified hydroxylated minor compounds in olive and sunflower oils has been developed and in-house validated. A satisfactory repeatability relative standard deviation (<7.5%) was obtained in all cases. The method, which requires simple instrumentation, allows for reliable quantification in a single chromatographic run with the advantages of minimizing sample manipulation, use of toxic solvents and reagents, and time consumption. The analytical procedure was applied to pure oil samples, including 15 authentic extra virgin olive oils collected from different European countries (Spain, Italy, Greece, and Portugal). Finally, the proposed SPE-GC-FID methodology could detect changes in the ratio between the free and esterified forms in pure extra virgin olive oil when mixed with refined sunflower oil at different percentages of 2, 5, 10, 15, and 20% (w/w) to simulate adulteration.
Highlights
The global trade of extra virgin olive oil (EVOO) has extensively increased during recent years due to its peculiar sensory characteristics, high nutritional values, and healthy benefits associated with its consumption [1,2]
The small addition of 2% of refined sunflower oil (RSO) in EVOO led to an increase of the esterified minor compounds from 360 to 410 mg/kg, with a simultaneous decrease of free and esterified components ratio from 4.7 to 4.1
The method proposed in this study allows for reliable quantification of both free and esterified hydroxylated minor compounds (HMCs) in a single chromatographic run with the advantages, compared to the methodologies already proposed in the literature, of minimizing sample manipulation, volume of solvents and reagents, and time needed for the procedure
Summary
The global trade of extra virgin olive oil (EVOO) has extensively increased during recent years due to its peculiar sensory characteristics, high nutritional values, and healthy benefits associated with its consumption [1,2]. EVOO and virgin olive oil (VOO), which are recognized as typical ingredients of the Mediterranean diet, are costly products and, fraud is frequent [3,4]. Particular attention must be paid to EVOO production and commercialization to guarantee compliance with quality and purity parameters specified by the EU, the International Olive Council (COI), and the Codex. With respect to the analytical methods available for purity assessment of olive oil, evaluation of the composition of sterols is a well-established tool, as the sterol profile depends on the botanical origin of oils [9].
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