Evaluating smell could spell success for food sector
odours, pushing back the boundaries of understanding smell, and
having implications for the food industry.
"I would say that people may be making decisions about the identity and perhaps even the hedonic quality of food flavours and aromas more quickly than previously thought," study leader Alan Gelperin told FoodNavigator.com.
Smell is intimately related to how human beings taste food but has long remained the most enigmatic of our senses. The average human nose can detect nearly 10,000 distinct scents, a feat achieved by 350 functional genes that code for olfactory receptors.
Exactly how the many thousands of different odorants are detected and identified remains a mystery. The human nose is thought to contain several hundred different types of olfactory receptors. Current understanding centres on perception of any one odorant involving simultaneous stimulation of several different receptors and that an olfactory code enables identification of specific odorants by the brain.
Previous experience and motivational state also interact with odorant information to influence processing and identification. It still is not known how the brain deals with all this information to let us perceive odours.
Moreover, very little is known if longer sampling times can lead to better accuracy. Scientists previously reported that humans can discriminate and identify odours with one sniff, and that longer or more sniffs don't change the outcome.
Researchers from the Monell Chemical Senses Center in Philadelphia have now challenged this by using an approach that has provided insight into information processing by the visual and auditory systems.
Gelperin and his colleagues used trained mice to ask whether longer exposure to an odour would result in more accurate identification of that odour. The results indicated that the mice needed extra time to accurately identify more complex odours.
"The well-trained mouse needs almost half a second to solve a difficult olfactory discrimination task," said lead author Dmitry Rinberg. "This time window is very important as we seek to design experiments and develop models that explain what the brain is doing in the extra time it takes to identify complex odours."
This work implies that mice need more sniffs to adequately discriminate between odours, particularly a mixture of odours that are similar, said the researchers in the August issue of the journal Neuron (Vol. 51, pp. 351-358).
"The development of colour television was based on extensive studies of visual sensory processing. Modern MP3 players are built based on a deep knowledge about properties of our hearing capabilities," said Rinberg. "Similarly, increased knowledge of olfactory processing has the obvious potential to open many doors, perhaps including development of electronic olfactory systems."
Indeed, electronic noses were launched commercially in 1995, and are computerised tabletop units with sensors that detect odour molecules. In recent years researchers on both sides of the Atlantic have shown the noses can be useful tools to save costs through their ability to detect the quality of products.
Areas to date touched on by the electronic noses include detecting the flavours of different kinds of cheese, sniffing the quality of wine and coffee, and detecting fishy seafood before it gets to the consumer.
The work was welcomed by Dr. Tracey Hollowood from Nottingham University's Sensory Science Centre as an exciting piece of research that provides strong evidence in support of temporal integration in olfaction.
Dr. Hollowood told FoodNavigator.com that this was a very well designed, significant, but not unexpected, contribution to the understanding of olfaction, despite apparent contradictions in the literature."Previous studies in Terry Acree's lab at Cornell University have shown that perception of subthreshold aromas can be modified by repeated exposure. Furthermore work conducted here at Nottingham University has shown that temporal modifications in aroma delivery disrupt existing taste/aroma interactions," she said.
Gelperin told FoodNavigator.com that the work had implications for the food industry: "We show that if the odour evaluation task is more difficult, mice, and perhaps men, will need a bit more time to make an accurate decision."
"How to encourage consumers to take the time to get an adequate sample of a flavour or aroma - that is a suitable challenge," said Gelperin.
"The fact that human subjects will be able to make a more accurate decision with regard to identification and discrimination with longer exposure times is a reasonable hypothesis," said Dr. Hollowood.
"However, this may not translate into modification of a consumer's hedonic response - a very different perceptual construct compared to identification or discrimination. Furthermore, as Dr Gilperin points out, controlling a consumer's attention to a product is quite a challenge and would require a highly effective marketing strategy," she said.