Coffee adulteration uncovered using new method
Researchers from the Quadram Institute have developed a new technique to distinguish between superior Arabica coffee and cheaper, lower quality Robusta.
Using the new technique, a survey of ground roast coffee samples labelled as 100% Arabica found that 10% of these coffees contained significant levels of Robusta coffee.
Arabica coffee trades at up to twice the price of Robusta due to its superior taste, and because Robusta plants are higher yielding and easier to grow. This makes adulteration of Arabica with cheaper Robusta coffee an attractive possibility to fraudsters.
Distinguishing between the two types of coffee is difficult, especially when they have been roasted and ground. Tasting isn’t reliable for detecting undeclared blends, so identification relies on chemical analysis of the many different compounds in the coffee. The major components are broadly similar, so the analysis focuses on minor components to provide a characteristic ‘fingerprint’” for Arabica or Robusta.
The current standard analytical technique focuses on one chemical, called 16-O-methylcafestol, or 16-OMC, which it detects in Robusta, but not in Arabica. However, the method is expensive and takes three days, making it impractical for large surveillance studies to detect fraud.
To overcome this, researchers from the Analytical Sciences Unit at the Quadram Institute developed a new technique to detect 16-OMC in coffee, using a benchtop NMR spectrometer from Oxford Instruments. This uses radio waves and strong magnets to get detailed information about the molecular composition of a sample.
Using the benchtop NMR reduces the time taken to process samples from 3 days to 30 minutes, saving time and money. The instrumentation is robust, portable, and can be used by non-specialists, making it suitable for use in industrial situations.
The research was funded by the Biotechnology and Biological Sciences Research Council and published in the journal Food Chemistry.
To characterise the NMR “fingerprint” of Arabica and Robusta coffee, the scientists worked with colleagues from the Royal Botanical Gardens, Kew, who provided samples with a reliable provenance.
The method is sensitive enough to detect just 1% Robusta in an Arabica/Robusta blend.
“This is an important milestone for detecting fraud in coffee, as 1% is the generally accepted cut off between trace contamination, which might be accidental, and more deliberate adulteration for economic gain” said Dr Kate Kemsley from the Quadram Institute, who led the research.
The increased sensitivity of the new test led to an unexpected finding that Arabica does in fact contain low levels of 16-OMC. So rather than have a simple test for its presence, the researchers had to devise software to assess whether the level was above a certain threshold. Using the authenticated samples from Kew made establishing this threshold possible.
The researchers have used their technique to get an estimate of the levels of Robusta adulteration in ground coffee labelled as 100% Arabica. 60 different samples originating from at least 11 different coffee-growing countries and regions were purchased by Quadram Institute staff and collaborators from across the world.
“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.
Giles Chapman, Head of Intelligence at the Food Standard Agency’s National Food Crime Unit said: “We’re always keen to understand how scientific advances expand the range of tools which can be used to validate the authenticity of food products sold to UK consumers. This piece of work has generated some interesting insights which we will be looking to explore further.”
Although 90% of the samples tested by the team were ok, the results suggest some coffee may not be as high quality as it is being described. This affects the consumer, who is paying a premium price for an inferior product. But it also has major impacts on the coffee producers themselves. Most of the world’s coffee is produced by millions of smallholders, many of whom are from developing countries. Better surveillance, which this new technique could help deliver, will protect consumers as well as ensuring that these farmers receive a fair price for their produce.
Reference: 16-O-methylcafestol is present in ground roast Arabica coffees: Implications for authenticity testing, Yvonne Gunning, Marianne Defernez, Andrew D. Watson, Niles Beadman, Ian J. Colquhoun, Gwénaëlle Le Gall, , Mark Philo, Hollie Garwood, David Williamson, Aaron P. Davis, E. Kate Kemsley. Food Chemistry 2018, 248, 52–60 doi: 10.1016/j.foodchem.2017.12.034
About the Quadram Institute
The Quadram Institute is an interdisciplinary research centre at the forefront of a new era of food and health research. It brings together researchers and clinicians under one roof and houses one of Europe’s largest endoscopy units and a clinical trial facility. It focuses on lifelong health – from birth and throughout the lifecourse, increasing healthspan as well as lifespan. It undertakes both fundamental and translational research working with industry to accelerate innovation and bring novel therapeutics and new food products to patients and consumers.
Based on the Norwich Research Park, The Quadram Institute is a partnership between Quadram Institute Bioscience, the Norfolk and Norwich University Hospitals NHS Foundation Trust, the University of East Anglia and the Biotechnology and Biological Sciences Research Council (BBSRC).
The Royal Botanic Gardens, Kew is a world famous scientific organisation, internationally respected for its outstanding collections as well as its scientific expertise in plant diversity, conservation and sustainable development in the UK and around the world. Kew Gardens is a major international and a top London visitor attraction. Kew’s 132 hectares of landscaped gardens, and Kew’s country estate, Wakehurst, attract over 1.5 million visits every year. Kew was made a UNESCO World Heritage Site in July 2003 and celebrated its 250th anniversary in 2009. Wakehurst is home to Kew's Millennium Seed Bank, the largest wild plant seed bank in the world. Kew receives just under half of its funding from Government through the Department for the Environment, Food and Rural Affairs (Defra) and research councils. Further funding needed to support Kew’s vital work comes from donors, membership and commercial activity including ticket sales.
The Biotechnology and Biological Sciences Research Council (BBSRC) is part of UK Research and Innovation, a non-departmental public body funded by a grant-in-aid from the UK government.
BBSRC invests in world-class bioscience research and training on behalf of the UK public. Our aim is to further scientific knowledge, to promote economic growth, wealth and job creation and to improve quality of life in the UK and beyond.
Funded by government, BBSRC invested £469 million in world-class bioscience in 2016-17. We support research and training in universities and strategically funded institutes. BBSRC research and the people we fund are helping society to meet major challenges, including food security, green energy and healthier, longer lives. Our investments underpin important UK economic sectors, such as farming, food, industrial biotechnology and pharmaceuticals
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