How conventional breeding techniques may lead to a naturally decaffeinated coffee bean
In Nature for 24 June a group of biochemists from Brazil describe a method of producing a decaffeinated beverage without having to process a harvested crop of coffee grown in the usual fashion. They point out that, as a result of discovering the adverse effect of caffeine experienced by some coffee drinkers, the market for artificially decaffeinated beverage has risen worldwide until it comprises some 10 per cent of the total demand, despite the admitted loss of important flavouring constituents during industrial processing. They argue that it is practicable
to raise a crop of coffee that contains 50–70 per cent less of the alkaloid
by a process of genetic breeding.
A naturally low-caffeine variety of Coffea arabica has been discovered in Ethiopia
whose beans are of high quality for preparing a palatable coffee. By means of
intraspecific hybridisation, commercial varieties of arabica coffee plants might
be raised, and this variety is at present the most cultivated and most consumed
in the world. Moreover, biotechnological attempts have already been made to reduce
caffeine synthesis by impeding the effect of genes controlling key enzymes in
its biosynthesis.
A study of 3,000 coffee trees in Brazil revealed that three of 300 derived from
Ethiopia were almost free from caffeine, according to liquid chromatographic
analysis of methanolic extracts of the seeds, having in fact a mean caffeine
content of 0.76mg/g dry weight. This compares with a figure of 12mg/g for a commercial
cultivar of Coffea arabica. Leaves and other parts of the fruit were also deficient
in the alkaloid. These plants accumulated the immediate precursor of caffeine,
theobromine, indicating that caffeine synthase, which converts it into caffeine,
was deficient.
Thus, the naturally low caffeine content found in the new cultivars is unlikely
to be attributable to enhanced degradation of the end product. Using conventional
breeding techniques, a naturally decaffeinated C arabica bean is feasible, doing
away with the present need for solvent extraction.
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