High throughput authenticity screening of high value edible oils with benchtop NMR

The high value of edible oils such as olive and argan makes them economically attractive targets for adulteration. Argan oil is becoming increasingly widely used in areas from cooking to cosmetics due to its reported pharmacological effects. Because argan oil is recognised as a Protected Geographical Indication product of its native Morocco, supply is limited. These two factors have led to argan oil becoming one of the most expensive edible oils in the world, leading to increasing numbers of cases of adulteration.As a typical nut oil, argan oil is composed predominantly of triglycerides. In previous work with similar oils as well as meat speciation using animal fats, benchtop NMR analysis has been able to determine authenticity through measurement of the fatty acid composition of these triglycerides. Using samples of argan oil of documented origin, typical values of monounsaturated fatty acid content (47%) and polyunsaturated fatty acid content (32%) were determined. In addition, a group of compositional parameters that distinguish authentic argan oil has been determined. Using integrals derived from simple 1H one-dimensional benchtop NMR spectra, a nearest-neighbour class model has been developed to identify authentic and adulterated argan oil with minimal sample preparation and a measurement time of less than five minutes. The screening method identified several adulterated examples of argan oil in samples purchased at retail. More recently, it has been demonstrated that by applying a rank transformation pre-treatment to magnitude mode 1H NMR data this technique can be made robust across several instruments at different sites with different specifications and operators. This ensures consistency of results and opens the path to this technique becoming field deployable. This method can be extended to determine the authenticity of other high value edible oils including, olive, coconut, and avocado, clearly demonstrating the potential of benchtop NMR in ensuring food authenticity.