12 January - 20 June 2016

A consumer test for caffeine

13 August 14

In a recent paper published in The Journal of Agricultural and Food Chemistry, researchers at the University of Iowa describe a test for caffeine that is suitable for home use by consumers wishing to monitor and/or restrict their intake. The authors claim that their test is superior to established diagnostic tests in that it is highly sensitive (1-5 ppm), quick (results in one minute), unaffected by other components present in the sample products, and suitable for assessing caffeine levels in beverages (although not tea!), milk (including breast milk) and pharmaceuticals.

The test uses the enzyme caffeine dehydrogenase (Cdh) which, in the presence of a tetrazolium dye, detects caffeine. Cdh catalyses a redox reaction between the dye and caffeine, with the dye reducing to a brightly coloured product. Various dyes were tested in order to find the most suitable - ideally, it should show a clear colour change during the reaction, proportional to the amount of caffeine present - and iodonitrotetrazolium chloride (INT) was eventually decided upon. INT produced shades ranging from light pink to dark red dependent on the caffeine concentration, enabling a reference chart to be created to estimate caffeine concentration in pharmaceuticals. For beverages, however, due to the strong background colours present, the team aimed only to determine whether the test would work in a qualitative manner, ie differentiating caffeinated, decaffeinated and beverages with no caffeine. It was found that these categories could be clearly and accurately distinguished by the paleness or intensity of the colour produced.

The authors suggest that a consumer caffeine diagnostic test is needed due to the growing number of products containing caffeine and the move towards consumption guidelines (the US Food and Drug Administration has published guidelines for adults and pregnant women, and is considering the same for infants and teenagers). They argue that there is likely to be growing demand among consumers for a dipstick-style test to support them in making quick decisions about consumption of particular products, and that the Cdh test is a good candidate for adaptation into this form. [Eurekalert]

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