Abstract
The detection of adulteration in edible oils is a concern in the food industry, especially for the higher priced virgin olive oils. This article presents a low field unilateral nuclear magnetic resonance (NMR) method for the detection of the adulteration of virgin olive oil that can be performed through sealed bottles providing a non-destructive screening technique. Adulterations of an extra virgin olive oil with different percentages of sunflower oil and red palm oil were measured with a commercial unilateral instrument, the profile NMR-Mouse. The NMR signal was processed using a 2-dimensional Inverse Laplace transformation to analyze the transverse relaxation and self-diffusion behaviors of different oils. The obtained results demonstrated the feasibility of detecting adulterations of olive oil with percentages of at least 10% of sunflower and red palm oils.
Highlights
The detection of adulteration in high priced olive oils is a particular concern in the food industry.Virgin olive oil is pressed fruit without any additives and without the use of heat in the process; the best of these in terms of flavor are classified as extra virgin and must pass chemical tests in a laboratory and a sensory evaluation
We can see that the D-T2 distribution plot of different oils separate in the vertical direction (D-axis), but overlap in the lateral direction (T2-axis). It indicates that the adulteration of sunflower oil in the extra virgin olive oil can more readily be detected from the sample’s diffusion behavior
For the red palm and extra virgin olive mixed oils, the distributions are separated in D-axis, and in T2-axis. This indicates that the adulteration of red palm oil in the extra virgin olive oil can be detected both from the diffusion and transverse relaxation behaviors
Summary
The detection of adulteration in high priced olive oils is a particular concern in the food industry. Priego Capote et al developed an analytical method based on a gas chromatograph for the detection of extra virgin olive oil adulteration with four edible vegetable oils: sunflower, corn, peanut and coconut oils [7]. With more detailed NMR analyses, the diffusion coefficient of minor constituents of olive oil was chosen as a marker parameter [10,11] All these methods have been employed with some success, but there are some problems. This article presents an alternative method, namely low field unilateral NMR, with the same potential as Raman for operation ‘in the field’. With this method, the transverse relaxation and self-diffusion of different adulterated oils have been studied. The samples can be measured without any preprocessing operation and the unilateral magnet structure means that the oils need not to be taken out from their original bottles, which can remain sealed
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