Primary flavors and fragrances

The human eye can distinguish bazillions of different colors, but we know that all those colors are really just different combinations of the three primary colors.

My question is: Is there any analogous system of primary flavors and fragrances? Is it possible that any given smell is actually a combination of several basic primary smells?

Flavors – yes, sort of. There are four types of taste receptors on the tongue: sweet, sour, salty, and bitter. All flavors are combinations of these. HOWEVER flavor also includes an element of smell, too, which accounts for additional flavors. (Coffee, for instance, has no flavor; it’s all aroma.)

I don’t know if there’s the same sort of system for smells. The only suggestion for this I’ve seen was in Roald Dahl’s great short story, “Bitch,” though I wouldn’t expect that to be an authoritative source.

Well, I recall in a childrens’ book, The Case of the Bashful Bank Robber by Hildick (don’t remember the first name…it’s a McGurk mystery), one of the characters came up with a system for quantifying smell, separating it into “Sulfas” (since sulfur is the main element in most bad smells) and “Sucras” (for sweet smells, but I don’t know what the active element would be).

Perhaps there’s some scientific validity to that…there are only a few elements our noses actually detect, and the range of scents are combinations of them.

Chaim Mattis Keller

“Sherlock Holmes once said that once you have eliminated the
impossible, whatever remains, however improbable, must be
the answer. I, however, do not like to eliminate the impossible.
The impossible often has a kind of integrity to it that the merely improbable lacks.”
– Douglas Adams’s Dirk Gently, Holistic Detective

Are all colors just mixtures of the basic three? I’m not a physics major, but I was under the impression that a particular color corresponded to a particular wavelength of light, right?

In art, color is discussed as additive and subtractive color. Do you add color together to get white or subtract it? Paints are subtractive - you remove the different paint pigments to white. Colored light gels in the theater - red, blue, and green - are added together to make white light (or did I just answer my own question from the first paragraph?).

phouka writes:

Yes, and yes. “A color” can correspond to a particular wavelength of light. But, humans have three color receptors - red, green, and blue. Each has a fairly broad band of response, so for example the wavelength for yellow trips the red and green sensors roughly the same amount.

Similarly, if your computer monitor shows you red and green right next to one another, your brain sees yellow because that’s how it has always interpreted the color yellow - equal red and green signals. So, both concepts of ‘color’ are valid.

Your eye can only see additive colors, so in the subtractive color combinations you end up with some of the additive components left behind for your eye to detect.

There probably are primary smells, but there are so many they’ve never been quantified. Many different organic chemicals have a distinct smell, and these chemicals are present in foods in varying quantities. Quantifying secondary smells would be even harder, since there are practically infinite combinations of the (several thousand?) primary smells.

Wine tasters are very good at distinguishing combinations of them - secondary smells, if you will. Some secondary smells are not very appealing, which is why a wine taster might say something like, “The hint of elderberry arrives late and completely impertinently after an arrogant dose of roses” (it’s hard to describe aromas sometimes).

An interesting tangent is that the olfactory part of the brain is located right next to the memory part. Ever smelt something that totally brought you to another place? Some kinds of dust bring me right back to my grandmother attic. Dogs are said to have a large catalog of smells - when they smell something for the first time they almost always remember it, and what it means.

Well, nobody has discussed differences in olfactory nerve endings. To have “primary” smells, one would expect there to be a small number of different types of such nerve endings. Is there such small number of types of nerve endings? There must be similar smell sensations from varied chemicals with the same radicals. But the aromatic ones probably have a fair mixture of radicals, huh?

I don’t know what I’m talking about here, but certainly there exist persons presently having knowledge of olfactory-nerve-ending chemistry, right?


You don’t need different nerve endings. Odorants bind to protein receptors. One olfactory nerve cell presumably has on its surface many different types of these receptors. Im guessing that several odorants that bind the same receptor would be in the same “class”.

Attempts to categorize odors are being done by researching the many protein receptors found in the nose. For example, the receptor for the odorant n-octanal has been recently identified. Great news, I know. I’ll give the article a quick read when I get to work tomorrow.

Haiqing Zhao, et al. Functional Expression of a Mammalian Odorant Receptor. Science 1998 279: 237-242

I knew I’d seen it somewhere, and finally got around to doing a search. (way at the bottom) says that there are a thousand or more smell-receptor genes. Lots better than three colours and four tastes. The article also says that 72% of those genes are defective in humans.

Bob the Random Expert
“If we don’t have the answer, we’ll make one up.”

The latest issue of Wired has an article about ‘DigiScent’–odour synthesis. Apparently there’s about a hundred primary odours. Now they’re talking about odour-enhancing video-games and web pages…

The box that sits on your desk and synthesizes odours from the basic components is called a ‘reeker’ (like ‘speaker’ for sound). And the device that captures and analuzes odours is either a ‘smell camera’ or ‘artificial nose’.

Page 256. November 1999 issue.