We tend to think of flavor as predominantly connected to our sense of taste, largely because we put food into our mouths and that is where our taste buds are located. But flavor is linked to all of our senses, in particular the sense of smell.
For this reason, the annual Smell Festival (May 21-25), held in the north Italian city of Bologna, has this year featured a workshop offering an introduction to neurogastronomy... food for thought to whet the appetite.
Maestro of neurogastronomy, herbalist Marco ValussiMarco Valussi, put together some simple experiments to reveal the basic precepts of neurogastronomy: from closing your eyes and pinching your nose then placing a mystery food in your mouth, to tasting a series of unknown liquids or describing the aromas of two different colored drinks.
Smell is the first and most important sense to explore in combination with taste.
Although they have distinct neurological pathways, Marco Valussi says the idea that we taste in our mouths but smell in our noses is not strictly true. Smell is what he calls a "dual sense" consisting of orthonasal and retronasal smell.
"This means the way we smell something by sniffing at something which is outside our body in the environment, and the way that we smell something when this something is inside our body, mainly inside our oral cavity, which means when we smell something that we're eating, chewing," says Valussi.
Valussi explains that it is impossible to separate retronasal smell from taste because they happen at the same time and in the same place and come from the same origin, namely, the food you are eating.
Do try this at home
There is a simple experiment anyone can try out to experience retronasal stimulation.
Cut some apple and onion into small cubes. Close your eyes, pinch your nose and put one cube in your mouth. If you only suck on it, you will not be able to perceive any difference in flavor. Once you open your nose, you will immediately understand if you have apple or onion in your mouth.
The reason, Valussi explains, is that we only have five taste notes, or tones: sweet, salty, bitter, sour and umami. But we can smell hundreds of millions of different olfactory stimuli.
"So it's quite obvious that when you put together the two, the final sensation is much, much richer than when you just use the five descriptors."
Most people who have suffered from a heavy cold will have experienced the effect of having a bunged up nose on their flavor perception: something like eating in black and white, instead of Technicolor.
Anosmia, which is the technical term for the lack of sense of smell, can be caused by trauma or illness. The effects of the phenomenon prove how important olfaction is.
"When you read or listen to interviews with people who suffer from anosmia," says Valussi, "they would say that every aspect of their life which has to do with sensuality...has been deeply impoverished by the loss of sense of smell."
Important as smell is, it is not the only sense which combines with taste to create flavor perception.
Consistency and temperature, which involve the sense of touch, are fundamental. But when the workshop participants are confronted with two glasses - one containing a white juice, the other a red juice - there is tangible surprise at how much visual perception also affects flavor.
Participants describe the red liquid as more intense, and choose adjectives linked to fruits of the forest. They describe the white liquid as more delicate and resembling green apples and light colored fruits. In reality, they are identical juices - one simply contains red food coloring. Marco Valussi says visual perception regularly influences our brain's reception of flavor.
"Because we look - well, we should at least look - at what we're eating, and the color and appearance of the food will determine our expectancies towards this food."
This expectancy will also change the way we perceive the food once it is in our mouths. So if we see a drink that is deeply colored, Valussi says, we tend to think that the drink will have a deeper flavor, "so when we drink it, we expect, and in part, we taste a deeper flavor than with a lighter drink."
While most people do not realize that the sense of hearing affects flavor perception, crisp (potato chip) manufacturers do. Marco Valussi says the pitch of the sound the crisp makes when you break it in your mouth partly determines the sensation of freshness.
"In experiments, when they give you crisps which make a lower pitched sound, you tend to think that the crisp is not as fresh and crispy and therefore as good as another one which has a higher pitch."
Mind over matter
Among the most fascinating aspects of neurogastronomy is the huge impact social and cultural factors have on our perception of flavor, creating a sort of mass mind over matter.
In one of the experiments, the group has to taste five sugar solutions and choose which is the sweetest. The majority choose the one flavored with vanilla, although they are all, in fact, identically sweet.
"A smell which is culturally associated with a sweet taste," Valussi explains, "is recognized by people who live in a culture that shares the same assumption and read as a sweetening agent, while it is not."
In other words, people think the vanilla sugar solution is sweeter just because they are used to eating vanilla with sweet things. If you add hot pepper to a sugar solution, people will tend to think it is less sweet because they are used to eating it with savory foods.
This becomes really interesting when we start to enjoy foods which, by the laws of nature, we should not. Things like chili pepper, which burns our mouth, or moldy blue cheese that smells like dirty feet.
"We learn that even if at the beginning the cheese seemed really awful but everyone else was eating it...it must be good and we start eating and enjoying it. It is a cultural thing and a family thing," he adds, "because we participate in a social group and that social group teaches us what is good and what is bad."
Incredibly, we can even overcome certain physiological responses which are deeply ingrained in our biology. We have a natural aversion to bitter things, since bitter often indicates that something is poisonous, yet beer is one of the world's most popular tipples.