Update: Perfect Coffee

According to Claire Bowles of the New Scientist, the art of roasting coffee may be on the way out. For centuries, experts have used their judgement to decide when beans are ready to become a punchy espresso or a smooth latte. Now a computer algorithm could put them out of a job.

Master roasters use the look, smell and taste of the beans as they cook, as well as listening for "crackings" as gases inside the beans react and explode. "Roasting coffee is a difficult process with many variables," says Alfredo Hernández from the Joint Research Unit for Food Process Engineering in Massy, near Paris.

"Only the master roaster can say how long to roast and at what air temperature for a specific kind of bean," Hernández explains. But now he has developed a computer model that he claims can simplify the process.

Consumers want plump, rich-coloured beans. So Hernández and his team used cameras linked to a computer to take snapshots of roasting beans every 20 seconds. A neural network then analysed each picture and learned to predict which roasting times and temperatures produced the best-looking beans. Hernández hopes the results can be converted into simple colour and size charts that less skilled operators can use.

But some coffee experts are worried. "What if the coffee doesn't taste any good?" says Attilio Sciannimanica, a roaster from Cosmorex Coffee in Canberra. Each batch of beans is different, he says, so roasting conditions that were right last week could incinerate the beans the next.