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Fluorescence spectroscopy utilizing benchtop and portable spectrometers with light-emitting diodes (LEDs) as a fixed excitation source has been used as a method for detecting food adulteration in various products, including honey, extra virgin olive oil, tea, and coffee  It is cost-effective, rapid, and sensitive, allowing for intact measurement. LED-based fluorescence spectroscopy is fast, accurate, and cheaper than using a laser.. Recent advancements in semiconductor technology have enabled the delivery of LEDs with commercially available wavelengths ranging from 370 to 470 nm, exhibiting significant light intensity.

In this paper (purchase required), the authors used the technique to develop a classification model to detect ground soy in ground-roasted Arabica coffee, and to differentiate Robusta and Liberica varieties.  The abstract gives no details of the reference samples used to construct or validate the model but it was limited to 2024 season samples harvested in Indonesia.

Photo by Nathan Dumlao on Unsplash

The authors of this paper (open access) used Fourier-Transform Ion-Cyclotron Resonance Mass Spectrometry (FT-ICR) to accurately profile and classify thousands of chemical components within different types of coffee.  They are making their list of components publicly available alongside the paper.

Their reference set of 130 coffees were purchased at market, rather than being of traceable origin, but were verified by documentation from the manufacturers along with morphological examination and classification using the German standard NMR method.

From this list of markers, the authors investigated those with the potential to discriminate based on the complex Maillard reactions of roasting processes and those that could discriminate coffee varieties.  They propose a group of 25 tryptophan conjugates of hydroxycinnamic acids that could be measured by conventional high-resolution LC-MS and used as specific markers for rustica coffee vs arabica.