in the garden

 

Jun 2003 Journal

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Science Notebook: More about coffee

A Money Programme on BBC2 examined the 'coffee wars' between Caffe Nero, Coffee Republic, Costa Coffee and Starbucks. Their ubiquitous outlets now offer customers pleasant venues for indulging in many varieties of coffee drinks ranging from black Italian espressos to American-style lattes with frothy milk. The latter is obviously a slimmed-down version of the whipped cream on Kaffee mit Schlag in Central European cafes.

Where did coffee originate? The traditional story tells of an Ethiopian goatherd named Kaldi who, some 12 centuries ago, noticed that his goats became frisky after eating the coloured berries from a certain bush. It was soon discovered that the large seeds inside the berries - the coffee beans - contained a strong stimulant. This substance was caffeine, first extracted from coffee beans in 1820 by the German chemist Runge after his friend, the poet Goethe, had asked him to find out why he could not sleep after drinking coffee. In 1900 another chemist, Roselius, discovered that the caffeine could easily be removed with a suitable solvent after the raw beans had been pre-treated with steam to swell them. To make decaffeinated coffee commercially, he set up the company Kaffee HAG, whose name suffered a public image problem when its product was marketed in England. Nowadays, some 11% of coffee sold in Britain is decaffeinated. The extracted caffeine is not wasted - it is used in cola drinks and in certain preparations like headache powders.

Despite its stimulating effect, coffee did not become popular until the thirteenth century, when the crucial step of roasting the coffee beans was introduced. This turned infusions of the beans from an insipid to an extremely palatable beverage. Today, roasting is carried out in industry by passing hot gases at around 400°C through a bed of tumbling coffee beans. During this process the sucrose sugar and proteins in the raw beans decompose to form a large variety of other compounds which are responsible for the agreeable flavour and smell of coffee. Its pleasant aroma is now known to be made up of over 850 different substances.
Prof Michael Spiro

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