Lawrence LeBlond for redOrbit.com – Your Universe Online
When it comes to white, we use our senses in different ways to make astute judgments of what we are seeing, touching and perhaps hearing. Now, researchers from the Weizmann Institute of Science in Israel are showing us what white smells like.
The color white is a blend of many different wavelengths of light. When you mix a few colors you get a brand new color, and with a mix of several colors, eventually white is created. Other research shows that the same concept applies to sounds. If you combine tones of different frequencies, you eventually arrive at a perceptual hum called “white noise.” Going a step further, researchers Tali Weiss and Kobi Snitz, said the same can be said for smell. By mashing together an ensemble of distinct smells, you are inherently left with “white odor.”
Publishing their work in this week´s Proceedings of the National Academy of Sciences (PNAS), Weiss and Snitz unveil Laurax (or “olfactory white”). Laurax is a new fragrance, which according to a panel of sniffers, is neither appealing nor revolting–the most common response is that it is “intermediately pleasant.”
While the fragrance will unlikely be featured in any top magazine perfume ads, the scientific implications of this creation are fascinating. The researchers happened onto the scent by mixing together sets of completely different fragrances that all ended up smelling roughly the same. The team says Laurax is the odorous version of “white.”
By mashing up groups of differently-scented molecules, Weiss and Snitz were able to create complex mixtures that all smelled the same–even when none of the ingredients shared any common traits. They noted that the result is not a specific odor, but more like a unified perception.
Perhaps the oddity seen here is the fact that with uniquely pleasant odors, such as the smell of coffee or the scent of a rose, complex mixtures of chemicals are implemented naturally to produce such distinctive and easy to recognize smells. But in the lab, abundantly mixing uniquely-distinct chemicals always produce the same end result.
Weiss and Snitz produced their concoctions working with 86 single-molecule odors that hailed from all corners of “perceptual space.” They diluted the individual components of each molecule so they all smelled equally intense, and then mixed them into nearly 200 groups, each containing between 4 and 43 ingredients. They enlisted the help of 59 sniffers to rate their concoctions, which were doled out in pairs for the volunteers to make comparative judgments.
The team found that “the more components there were in each of two mixtures, the more similar the smell of those two mixtures became, even though the mixtures had no components in common”. As more and more unique components were added to the two concoctions, the more similar they smelled. And by adding enough chemicals, everything smelled the same.
Going further, the duo created four fragrances, each made from a different subset of 40 ingredients, and labeled each as “Laurax.” They asked a dozen volunteers to familiarize themselves with one of the four scents over a three-day period.
On the fourth day, the volunteers had to assign labels to four new mixtures containing between 1 and 40 components; the choices were “Laurax” and three other names given by a professional perfumer. The volunteers were more likely to describe a fragrance as “Laurax” if it had a large number of ingredients, even if the ingredients were very different than the original blend they had initially become accustomed to.
When blends were at 21 ingredients, the volunteers could easily tell the concoction was not “Laurax.” But when the blends reached 30 ingredients, volunteers labeled them as “Laurax.”
The team noted that the various olfactory whites weren´t entirely identical. Some of the volunteers were still able to distinguish between different versions of “Laurax.” Based on the data, the sniffers had no trouble ruling out smells as olfactory white when the blends were unevenly balanced, and when they included less than 30 ingredients.
But the key finding is that olfactory white may not even exist in nature. Most natural aromas have ingredients that number in the hundreds or perhaps thousands, and many are not as diverse in chemistry, or as balanced in intensity, as those found in Laurax. A rose, for example, may have hundreds of unique molecules, but just one of these–phenylethyl alcohol–accounts for 70 percent of the mixture. But, if you smell this molecule alone, you will unlikely smell a rose.
Like previous research into white light and white noise, Weiss and Snitz’s research into white odor has taught researchers a lot about how our sense of smell works. The duo are now planning to study brain activity of volunteers as they take a whiff of “Laurax.” The researchers have also submitted a patent “for a wide range of potential applications for olfactory white.”
“On the one hand, the findings expand the concept of ℠white´ beyond the familiar sight and sound. On the other, they touch on the most basic principles underlying our sense of smell, and these raise some issues with the conventional wisdom on the subject,” Professor Noam Sobel, head of the lab where Weiss and Snitz conducted their work, said in a prepared statement.
The most widely accepted view, for instance, describes the sense of smell as a sort of machine that detects odor molecules. But the Weizmann study implies that our smell systems perceive whole scents, rather than the individual odors they comprise, Sobel added.
Professional perfumer Danyel Gafsou described the various olfactory white blends as unique. When volunteers were asked to rate the blends according to 147 different descriptions, they avoided specific words like “leather” and “coffee,” and chose more generic terms such as fragrant, chemical, perfumery, floral, soapy and medicinal. Compared to most smells, “Laurax” seems to fall right in the middle between pleasant and unpleasant. According to the team, its as intermediate as you can get.
Weiss and Snitz said: “the best way to appreciate the qualities of olfactory white is to smell it.” And so they listed three recipes for “Laurax,” two of which share no components. But for the third, they suggest one mix and enjoy.
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