Identification of Coffee Arabica and Robusta

Coffee is the drink of mankind. After water the most commonly consumed drink. In a report by Euromonitor, coffee gulpers outnumber tea guzzlers in most countries around the globe. Coffee is multi billion dollar business. The price of coffee depends on many factors. One parameter stands out though, the type of coffee, Robusta or Arabica. How can we know coffee is cheap Robusta or the less bitter but more expensive Arabica. Recent scientific publications suggest to use modern Magnetic Resonance (MR) to look for certain chemical markers to identify the different species (see Monakhova et al., Food Chemistry 182 (2015) 178–184). These investigations have been carried out with expensive spectrometers which require liquid helium and nitrogen to keep the strong magnet in operation. These instruments are large and complicated and hence impossible to be operated by a coffee trader.

Identification of coffee species by Benchtop Magnetic Resonance
Recent advances in magnet technology combined with advanced signal processing allows to perform magnetic resonance without the need of large, helium gulping magnets. It is possible to acquire magnetic resonance signals in a office / coffee shop / home environment. A USB cable connects the instrument to a notebook computer, similar to a printer or scanner.
Fig 1. Bench Top MR System in the office

The measurement is straight forward. Mix a a few grains of coffee with a cheap solvent, fill it into 5 mm glass tube, insert into the instrument and press GO. The observed result will show the chemical markers. To demonstrate this we  measured 3 different coffee capsules from Segafredo.
Fig 2. Segafredo capsules to be measured by MR

The results of the measurement show:
  • one species contains no caffeine
  • one species contains Robusta components
  • one species contains no Robusta component
Fig 3. observed MR signals from 3 different capsules

Moreover the spectra look different for the three capsules measured. This may come from the different origins, treatment etc.
We applied a straight forward Principal Component Analysis (PCA) to show the overall distinctness of the capsules.
Fig 3. Discrimination of three coffee capsules by MR
By choosing the instrument parameters (e.g. measurement time) the magnetic resonance signal can be intensified to determine absolute amount of the identified chemicals (e.g. caffeine).
All of the conclusions from scientific publications performed on large instrument can readily be applied to the results on Bench Top MR systems. Some peaks may overlap due to smaller magnetic fields used for Bench top Instruments.

Due to their size, ease of use and cost, bench top MR instruments can be used in many applications for quality control and assurance. No specialist knowledge is required to run the experiments.
Joe the coffee trader has now a handy tool to proof the quality of his coffee.

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