Raman spectroscopy for verification and contamination ID of edible oils

Abstract: Counterfeit and adulterated edible oil products are of significant concern to producers and sellers seeking to maintain integrity and to governments from a food safety perspective. Most spectroscopic methods, such as NIR or NMR, can only identify or classify an oil, missing out on contamination from dyes or pesticides. Chromatography-based analyses can be highly specific and sensitive to trace compounds, but have greater sample preparation and ongoing operating expenses. These drawbacks can make it difficult to combat fraud and ensure safety outside of a stringent quarantine and testing regime.

Raman spectroscopy allows for highly specific differentiation of edible oils, by type and class. Because of the specificity, it is possible to use Raman to identify adulteration and substitution, determining one or more components of a mixture. A more specialized Raman technique, surface enhanced Raman spectroscopy (SERS), can also be applied to detect trace contaminants, such as pesticides and herbicides.

In this paper, we demonstrate how a single Raman system can be used to solve the adulteration, counterfeit, and contamination problems - reducing both operating and testing costs. We show specificity through a confusion matrix analysis of 16 pure edible oils. Then choose a subset for adulteration with each other, demonstrating semi-quantitative mixture analysis. Finally, we show the ability to detect fenthion pesticide at levels below the 1ppm regulatory limit.