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Electronic nose knows quality coffee
Machine could assist efforts to reproduce the perfect espresso
By Bryn Nelson
MSNBC
March 10, 2008
“We do not attempt to replace human tasters by instruments but to assist human tasters,” said Nestlé
researcher and lead author Christian Lindinger, whose report was published last month in the journal
Analytical Chemistry. “But in some cases we can use the approach as a pre-screening tool to eliminate those
samples which would anyhow fail a sensory evaluation because of insufficient quality.”
The perfect espresso
Researchers already have developed prototype electronic noses to analyze perfumes and wines as well as
to monitor landfill odors, distinguish between smoke from fires or cigarettes, warn of hazardous gases or
narcotics and even detect the warning signs of pneumonia and asthma in a person’s breath.
With more than 1,000 organic compounds contributing to a roasted coffee’s aroma, sniffing out the perfect
espresso has lagged behind a bit. Recent research, however, has suggested that only 50 of those chemicals
might be necessary for mapping out the sensory profile of that aroma — and perhaps even less for accurately
reproducing it.
For their study, the researchers used a standard espresso machine (made in Switzerland, of course) to
prepare the different samples. The team poured each one into a setup that allowed the espresso’s heated
gases to waft up from an oven to a chemical detector known as a proton-transfer reaction mass spectrometer.
The mass spectrometer recorded the prevailing gas mixture and a mathematical model then translated the
most useful chemical information into a more understandable description.
Lindinger said the model can predict the sensory profile of an unknown espresso based solely on the
chemical measurements. It’s also possible, he said, to discern the mix that correlates with a specific attribute
like, say, flowery notes, provided that the right balance of compounds is carefully recorded.
With their human noses to guide them, an in-house panel of 10 experts from across Europe also evaluated
each espresso on its range of attributes, scoring each as weak, medium or high-intensity. One espresso was
noted for its strong “butter toffee” quality, while another scored best on its “woody” attribute and a third was,
alas, deemed particularly “bitter.”
'Nose' to nose with the pros
Lindinger and his co-authors cautioned that an intense coffee can be a headache when trying to
dispassionately summarize not only its attributes but also the relative strengths of each. One taster might
judge an overly bitter coffee as rather intense, while another expert could just as easily be influenced by a
coffee’s evident acidity. Such quality versus quantity distinctions are important because the study included
espressos made with varying amounts of water that could dilute or concentrate some smells.
Even so, the panel and machine matched up remarkably well on nearly every espresso’s qualities, although
they did, on occasion, beg to differ about the intensities. Did that one really have a high-intensity roasted and
bitter aroma, as the experts thought, or only a medium level, as the electronic nose judged?
Only one espresso seemed to defy a uniform judgment, as the panel pointed to its intense butter toffee and
cereal qualities (the machine did not), while mostly thumbing their noses at what the machine judged to be its
moderately bitter, cocoa and coffee elements.
Machine could assist efforts to reproduce the perfect espresso
By Bryn Nelson
MSNBC
March 10, 2008
- Ah! A bold espresso that boasts intense
flowery, winey, citrus, acid — and yes,
even butter toffee notes. So says an
electronic nose, anyway.
Behold, the coffee snob of the future.
Perhaps the machine assembled by
scientists at the Nestlé Research Center
in Switzerland isn’t quite ready to be
called into daily demitasse-sipping
service. But in an analytical test of its
abilities, it predicted the range of aromas
and intensities noted by a panel of
experts for 11 different espressos, with
few mismatches. And in a subsequent
validation, the electronic nose nearly
duplicated the panel’s opinion in
characterizing an additional eight
espressos.
- In the quest for consistently high-quality
java, the coffee industry stands to benefit
enormously from any nose that really
knows its stuff, whether attached to a
person or a machine.
“We do not attempt to replace human tasters by instruments but to assist human tasters,” said Nestlé
researcher and lead author Christian Lindinger, whose report was published last month in the journal
Analytical Chemistry. “But in some cases we can use the approach as a pre-screening tool to eliminate those
samples which would anyhow fail a sensory evaluation because of insufficient quality.”
The perfect espresso
Researchers already have developed prototype electronic noses to analyze perfumes and wines as well as
to monitor landfill odors, distinguish between smoke from fires or cigarettes, warn of hazardous gases or
narcotics and even detect the warning signs of pneumonia and asthma in a person’s breath.
With more than 1,000 organic compounds contributing to a roasted coffee’s aroma, sniffing out the perfect
espresso has lagged behind a bit. Recent research, however, has suggested that only 50 of those chemicals
might be necessary for mapping out the sensory profile of that aroma — and perhaps even less for accurately
reproducing it.
For their study, the researchers used a standard espresso machine (made in Switzerland, of course) to
prepare the different samples. The team poured each one into a setup that allowed the espresso’s heated
gases to waft up from an oven to a chemical detector known as a proton-transfer reaction mass spectrometer.
The mass spectrometer recorded the prevailing gas mixture and a mathematical model then translated the
most useful chemical information into a more understandable description.
Lindinger said the model can predict the sensory profile of an unknown espresso based solely on the
chemical measurements. It’s also possible, he said, to discern the mix that correlates with a specific attribute
like, say, flowery notes, provided that the right balance of compounds is carefully recorded.
With their human noses to guide them, an in-house panel of 10 experts from across Europe also evaluated
each espresso on its range of attributes, scoring each as weak, medium or high-intensity. One espresso was
noted for its strong “butter toffee” quality, while another scored best on its “woody” attribute and a third was,
alas, deemed particularly “bitter.”
'Nose' to nose with the pros
Lindinger and his co-authors cautioned that an intense coffee can be a headache when trying to
dispassionately summarize not only its attributes but also the relative strengths of each. One taster might
judge an overly bitter coffee as rather intense, while another expert could just as easily be influenced by a
coffee’s evident acidity. Such quality versus quantity distinctions are important because the study included
espressos made with varying amounts of water that could dilute or concentrate some smells.
Even so, the panel and machine matched up remarkably well on nearly every espresso’s qualities, although
they did, on occasion, beg to differ about the intensities. Did that one really have a high-intensity roasted and
bitter aroma, as the experts thought, or only a medium level, as the electronic nose judged?
Only one espresso seemed to defy a uniform judgment, as the panel pointed to its intense butter toffee and
cereal qualities (the machine did not), while mostly thumbing their noses at what the machine judged to be its
moderately bitter, cocoa and coffee elements.
Introduction
Could an electronic nose developed by Nestlé be the ultimate coffee snob of the
future? Company researchers say the ability of their machine to differentiate among
flowery, winey, bitter, cocoa and other espresso attributes could help with quality
control. -- Bryn Nelson
Could an electronic nose developed by Nestlé be the ultimate coffee snob of the
future? Company researchers say the ability of their machine to differentiate among
flowery, winey, bitter, cocoa and other espresso attributes could help with quality
control. -- Bryn Nelson