Detection of Robusta species in Arabica coffee beans

How do I know if my coffee beans are Arabica or Robusta?

Both types of coffee beans are the most known around the globe. Arabica type accounts for 60% of the whole production, characterized by a more smooth, rich flavor. Whereas Robusta, which produces a more bitter drink, is easier to yield, hence the price is much cheaper. (International Coffee Organization, 2021)

In the last years, it has been observed that some producers try to decrease their costs by adulterating Arabica coffee with the Robusta type. Interpol’s recent investigations show that the issue is growing on a large scale, it was found that some larger producers of Arabica coffee beans were adding up to 10% of Robusta type in their consumer mis-sold goods. (bvl.bund.de, 2019)

Authentication efforts of Arabica coffee

There are several methods to determine the purity of the coffee, such as liquid chromatography, magnetic resonance spectroscopy, or molecular genetics. However, all those methods, are time-consuming (sample preparation) and performed in specialty laboratories, hence not suitable for rapid and non-destructive analysis.

The researchers from the Austrian Centre of Nuclear Techniques in Food and Agriculture explored more innovative ways of analyzing coffee beans to speed up and improve the current processes. A newly released peer-reviewed paper from Food Chemistry: X, illustrates how the VideometerLab technology can be successfully utilized for the detection of Robusta beans in Arabica coffee.

How to detect adulteration with spectral imaging?

This study was divided into two parts – discrimination of Arabica and Robusta coffee beans and their adulteration. The samples were obtained from a trusted supplier in Germany. The model for discrimination was built on 3500 unique coffee beans, whereas the training data set for detection of adulteration was based on 4200 samples.

Discrimination between the two coffee beans was achieved by spectral, morphological, and color features using VideometerLab Software. The predictive ability was established to be 0.834 and goodness to fit resulted in 0.909. Using various wavelengths, assisted with the identification between Robusta and Arabica coffee beans. It is important to mention, that the results may differ depending on the geographical origins of the sample or roasting degree, to achieve a standardized model in the future the sample ought to be more differentiated in regards to these criteria.

When it comes to the adulteration experiment, different levels of contamination have been used to assess the capability and effectiveness of spectral imaging technology in this application. The results have shown 100% of correct classification, the study concluded that the VideometerLab system, combined with OPLS-DA, is a promising tool for the differentiation between Robusta and roasted Arabica coffee beans.