Decaffeinated makes up 10% of the world's coffee market. Credit: © GettyImages

Decaffeinated coffee is growing on trees in Japan. The genetically modified bushes could yield low-caffeine beans within three or four years1. Whether consumers will prefer them to chemically decaffeinated beans remains to be seen.

Coffee is currently stripped of caffeine in expensive industrial processes. Carbon dioxide or organic solvents flush the caffeine from beans, often along with other key flavour compounds. The resulting taste can send connoisseurs racing for a full-jolt fix, despite its negative effects on health. The alternative, more costly Swiss Water Process sieves out caffeine through a carbon filter, leaving a fuller-flavour brew.

"Theoretically the new bean should taste like normal coffee," says Hiroshi Sano from the Nara Institute of Science and Technology in Japan, whose team produced the plants, now a year old.

That the coffee might be cheaper and in some ways safer than other decafs does not mean the public will buy it. Whereas the US is largely indifferent to GM products, UK pressure groups have powerful concerns. The British government is currently canvassing public opinion before it decides whether to allow the commercial planting of GM crops.

Reactions could be favourable because there are clear benefits to the consumer, suggests plant geneticist David Baulcombe from the John Innes Centre, Norwich, UK. "It's in contrast to herbicide-tolerant and insect-resistant lines, where the benefit is for the farmer and the environment."

With more than 10% of the world's coffee market decaffeinated, demand for a flavoursome low-caffeine blend is high. Full-strength coffee can raise blood pressure, trigger palpitations and disrupt sleep.

But companies have invested a lot of money in decaffeination factories, so they too may be reluctant to switch. Before full-scale production can go ahead, "there needs to be a market demand," says plant-products expert Alan Crozier of Glasgow University's Institute of Biomedical and Life Sciences.

The new plants lack a key caffeine-making gene. They produce up to 70% less of the stimulant than normal plants, bringing their levels in line with chemically decaffeinated beans.

The shrubs are a derivative of Coffea canephora, a variety commonly used for blending. The next step is to modify the slower-growing Arabica plant, which produces high-quality beans and accounts for 70% of the worldwide coffee market.