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By Richard Gray, Science Correspondent 8:00AM BST 28 Aug 2011It has caused coffee manufacturers sleepless nights: could there be a caffeine-free coffee which actually tastes like the real thing?
The search for a stimulant-free alternative has often proven less than fruitful, with versions of the drink which lack not just caffeine's kick, but flavour.
Now scientists claim to have found a possible solution in a type of pistachio nut.
They claim that carefully roasted, the fruit of the Pistacia terebinthus tree, which is much smaller than normal pistachios, could offer all the flavour of coffee, with none of the kick - as well as being significantly cheaper.
It might seem an unlikely boast, as the special type of pistachio nut is from a tree better known as having sap which is a source of turpentine.
But chemists at the University of York say that pistacia has the same chemical "signature" as real, caffinated, coffee - meaning it can be made to have the same taste and aroma.
The researchers found that when they roasted the P. terebinthus nuts for 20 minutes at 200 degrees they started to show a volatile chemical profile similar to roasted coffee beans.
The roasting produced high amounts of chemicals that give the nuts a caramel and burnt sugar smell along with a slight citrus and pine flavour.
Green coffee beans need to be for around 10-15 minutes and the roasting process changes the flavour of the final coffee.
But can this really be true?
The Sunday Telegraph put the coffee alternative to the test - to see if the truth could be filtered out.
We challenged Danielle Hadley, a judge for the UK Barista Championships and a committee member of the UK chapter of the Speciality Coffee Association of Europe, to test the pistachio coffee substitute against a standard cup of coffee.
我们邀请英国咖啡师锦标赛的评委，同时也是欧洲专业咖啡协会（Speciality Coffee Association of Europe）英国分会的执行委员Danielle Hadley女士来品鉴开心果“咖啡“和真正的咖啡。
The raw nuts look and smell like normal pistachios.
But when roasted they took on a rich, nutty coffee-like aroma.
First Miss Hadley brewed the pistachio coffee in the same way as a traditional Turkish coffee, producing a rich, dark brown drink with a chocolate and nutty smell.
"There is not much of a creme, which is where the oils from the coffee sit on the surface, from the pistachio drink," said Miss Hadley.
"It smells nutty and it is more woody, like fresh pine, than coffee. There is a hint of plastic in there too.”
"It has quite a distinctive flavour, but I'm not sure it is a perfect substitute for traditional coffee. It does smell really nice and I could see why it might take off."
Then we tried the more challenging test: could it be used to create the perfect espresso.
The result suggested pistachio coffee might not take off in trendy coffee bars.
The roast nuts turned into an oily paste, which did not lend itself to espresso - the thick paste did not let much water run through and the result was bitter and oily.
Miss Hadley, who runs her own coffee distribution and training company called Danielle's coffee, said: "Compared to a premium blend of normal coffee, I would pick the traditional stuff every time."
Jeremy Wood, a coffee and training manager at coffee wholesalers Masteroast in Peterborough, added: "It has a really woody and spicy flavour.
"Coffee prices are high at the moment so this could provide an alternative. When coffee beans are roasted we change the temperature during the roasting to enhance the flavour so perhaps the nuts would benefit from that too."
The researchers hope to fine tune the roasting method while also reducing the oil content of the ground P. terebinthus nuts so they can be sold commercially.
Currently the nuts grow wild in parts of Turkey but the crop could be easily commercialised.
Dr Mustafa Ozel, of the University of York said work could now be done to perfect the coffee alternative - opening the way to passing the espresso test.
"The roasting process can be manipulated to bring out different flavours and minimise any deleterious compounds produced," he said.
"While the overall chemical composition is not similar to coffee beans, the final roasted product has a similar volatile composition."