Nuclear Magnetic Resonance spectroscopy and Multivariate Statistical Analysis: A Robust Approach for Avocado Oil Authentication

Avocado oil is a prominent edible oil in the global market, highly sought for its beneficial health attributes due to high monounsaturated fatty acid, carotenoids, and polyphenol contents. The popularity has attracted severe adulteration with lesser-grade oils such as corn, safflower, sunflower, soybean, and others, mainly to overcome shortage in global supply, and cost cutting. Whilst chromatographic methods are conventionally employed in assessing the quality of oils, these are cumbersome, time consuming and laborious. Moreover, the fatty acid profile of avocado oil is heterogeneous as it is influenced by the processing and manufacturing conditions, therefore demanding robust analytical methods which can accurately capture and probe such large chemical variance. Nuclear Magnetic Resonance (NMR) spectroscopy and multivariate statistical analysis (MSA) were employed to address these analytical challenges. Authentic avocado oils and those blended with adulterants were analyzed using proton NMR spectroscopy and a spectral library of untargeted and semi-quantitative analytical capabilities was built. Statistical methods such as hierarchical clustering, and dimension reduction methods such as principal component and linear discriminant analyses were employed to differentiate authentic and adulterated samples. These samples were parallelly analyzed using gas chromatography (GC) as per the Association of Official Analytical Chemists (AOAC) guidelines. The NMR-based spectroscopic data and statistical models clearly differentiated authentic adulterated oils with high confidence and identified the source of adulteration, cross-validated by the corresponding GC data. NMR spectroscopy in conjunction with MSA proves to be a robust analytical method that can compete effectively with current analytical methods with additional benefits such as reliability, ease of use, high throughput sampling, minimal sample preparation steps, and easy data interpretation. In addition, the spectral library offers analytical capabilities to test batch-to-batch consistency, increasing the value of NMR spectroscopy in edible oil analysis.