A bitter business – scientists find inferior coffee in ‘superior’ blends

COFFEE drinkers are being conned by suppliers fraudulently mixing inferior beans into products labelled 100 per cent arabica, scientists claim.

A study by British researchers testing a new and more accurate method of gauging coffee quality examined coffee on sale at shops and supermarkets.

They found that a tenth of high-qual- ity products labelled “100 per cent arabica” contained significant levels of inferior and cheaper robusta beans. Arabica coffee trades at twice the price because of its superior taste.

Finding rogue robusta, which has a more bitter taste, in a sample labelled arabica is not easy, especially after grinding and roasting. The standard technique detects the fingerprint chemical 16-OMC, which is only found in robusta coffee, but the process is costly and takes three days, making large-scale surveillance impractical.

The new method takes just 30 minutes and is sensitive enough to detect 1 per cent robusta in a blended coffee.

Dr Kate Kemsley, the lead scientist from the Quadram Institute, formerly the Institute of Food Research, said: “This is an important milestone for detecting fraud in coffee, as 1 per cent is the generally accepted cut-off between trace contamination, which might be accidental, and more deliberate adulteration for economic gain.”

For the study, 60 different coffee samples were purchased around the world, including 22 from the UK. All were tested for 16-OMC using the new nuclear magnetic resonance technique, which employs radio waves and strong magnetic fields to obtain detailed information about a substance’s molecular composition. “It was immediately obvious using our test that there were several suspicious samples, producing results that were consistent with the presence of substantial amounts of robusta – far more than would be expected through unavoidable contamination,” said Dr Kemsley.

Two of the samples flagged as “suspicious” were bought in the UK. One contained 1.6 per cent robusta and the other 21.7 per cent. Other UK samples had notable levels of 16-OMC but fell below the “suspicious” threshold.

Suspicious samples were also purchased from the US, Italy, France and Estonia. One US sample was a third robusta, despite being labelled 100 per cent arabica.

The research, published in the journal Food Chemistry, was funded by the Biotechnology and Biological Sciences Research Council and had no support from the coffee industry.