Electronic ‘Nose’ Technology Finds Novel Applications
In recent years, Dr. Kumar Mallikarjunan, associate professor of Biological Systems Engineering, has acquired some highly specialized equipment that makes it possible to detect and identify the chemical signatures of tens of thousands of different airborne compounds. These electronic ‘noses’ are more sensitive than the most discriminating human or dog noses, and can provide hard evidence where previously only conjecture could be offered.
For example, the equipment has been used to detect the adulteration of honey by adding corn or other sweeteners, a practice that does not recognizably alter the flavor of the honey but that does affect its ability to be labeled and sold as pure honey. Honey manufacturers who previously could simply deny that they were adulterating their product cannot do so any longer, because of the electronic nose’s ability to pick up on even the faintest chemical signature that is inconsistent with a certain variety of pure honey. In addition to honey, Mallikarjunan’s lab has worked on detecting the subtle smell of trace chemicals in printed packaging, warmed-over flavor in meats, and rancidity in roasted peanuts. The equipment has also been used to help restaurants determine exactly when to change out the oil in their fryer vats.
Mallikarjunan’s lab is equipped with several handheld
units, as well as a larger and more complex bench model. In a recent Sea Grant
funded project led
by graduate student Amy Hu, the effectiveness of two different hand-held electronic
nose systems was assessed. The electronic noses were used to describe the quality
of live oysters stored at 4 and 7° C for 14 days. Electronic nose data were
correlated with trained sensory panel evaluations using Quantitative Descriptive
Analysis (QDA), as well as with microbial enumeration. The study found that oysters
stored at both temperatures exhibited varying degrees of microbial spoilage,
with bacterial load reaching 107 (the 7 should be superscripted) CFU/g at day
7. The Cyranose 320 electronic nose system having conducting polymer based sensors
was capable of generating a characteristic “smell print” that made
it possible to differentiate the quality of oysters of varying age (100% separation).
The results showed that Cyranose 320 could identify the quality of oysters
in terms of storage time with 93% accuracy. 
Comparatively, the successful classification
rate for the VOCChek electronic nose, a system based on quartz microbalance
sensors,
was only 23%. Correlation of electronic nose data with microbial counts suggested
that Cyranose 320 was able to accurately predict microbial contamination in
the oysters. Correlation of sensory panel scores with electronic nose data
revealed
that electronic nose has demonstrated potential as a quality assessment tool
by mapping varying degrees of oyster quality.
Left-top: Handheld electronic nose devices such as the VOCChek (left) and the Cyranose 320 make it possible to do in-depth analysis of smell compounds in the field.
Let-bottom: Dr. Mallikarjunan points out some of the features of the benchtop unit at his laboratory.
This work has applications for commercial seafood processors, distributors, and retailers. It could make it possible to tell, very quickly, whether products were still in saleable condition, saving time and money. The devices can retain the “smell prints” for a variety of different chemical compounds, and can be reprogrammed to detect different compounds as needs change.
For more information, contact Dr. Kumar Mallikarjunan by e-mail ( ).
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