I well remember the day I was going through a buffet line with my former supervisor, Percy. As we passed each entree, I told him the chemical name of the predominant flavoring or coloring in each food. When we got to those fake "crab" legs, with that red coloring on top, I told Percy that it wasn't crab at all, but a gelatinized cod that was colored with some red dye number 5. The woman ahead of us in line apparently had enough and asked me to stop talking. She wanted to enjoy her lunch. I assured her that, if the crab legs were real crab, the red color is not a dye, but a potent, highly-colored toxin. However, it was in low concentration, so it wouldn't put her into anaphylactic shock. I had the best of intentions.
My first career job as a chemist was in flavors and fragrances. I worked for a company that made natural and unnatural chemicals for foods and fragrances. This is a fascinating area of study, especially when I began to realize that chemicals are what stimulate our senses of taste and smell.
Our sense of smell depends upon air-borne molecules that are emitted by some source. How do molecules become air-borne? There are a couple ways. The principal way molecules become airborne is when they evaporate. Smaller molecules can just float right into the air. This should be nothing surprising. Water on the sidewalk after a rain will “disappear” due to evaporation. When you smell fresh fruit, like an orange, the fragrance components in the orange evaporate from the peel, and you can smell the molecules floating in the air.
Another way molecules become air-borne is when they are associated with small particles, such as dust or smoke. Cigarette smoke, for example, consists of microscopic particles. When you take in smoke from a cigarette or if you breathe second-hand smoke, you breathe in the particulates containing odor molecules. Generally speaking, breathing particulates, such as smoke or the air on a hazy day, is unhealthy. Particulates find their way into our lungs and are not easily expelled.
I believe that most smells we encounter are evaporated molecules. Although we associate smells with emotions such as enjoyment, feeling secure, or uncomfortable, smells are really much, much more than a way of affecting us.
For example, consider a fragrant rose. The principal chemical in that fragrance is a fairly simple one: phenethyl alcohol (pronounced: fen’-eth-il al’-co-hol). This is a molecule with eight carbons, one oxygen, and a bunch of hydrogen atoms. It almost completely captures the rose fragrance, right down to that slightly cloying note that you smell a few seconds into the experience. Roses have the machinery to make that chemical. Why would a rose want to make phenethyl alcohol? Darwin's Theory of Evolution has an answer. The phenethyl alcohol attracts beneficial insects, such as bees. Bees love the sweetness of roses and spend a good deal of time around them. In their rapture, the bees gather some pollen on their bodies and then fly off to another rose bush to get raptured all over again. The bees also collect some nectar for their honey manufacturing at the nest. So, it’s a natural win-win situation.
Nature has a very different way of “thinking” about a rose fragrance. Nature doesn’t really “care” if you enjoy the fragrance of her flower. “Enjoyment” may not even be in her vocabulary. I will tell you a word that is in her vocabulary: Information. The phenethyl alcohol in the rose is, to Nature, anyway, an information molecule. When the rose emits that fragrance, it’s say to the whole world: “Hey, all you bees and other beneficial insects out there, here I am. Just home in on my phenthyl alcohol and you will find me. Take my pollen and propagate me and my species.”
That phenethyl alcohol is also an information molecule to us humans. When we walk by a rose garden and take in that fragrance, a little voice in our heads says: “Wow! That smells so good! But, I know what I’m smelling just doesn’t smell good, I’m smelling an information molecule. It tells me that there is a rose garden nearby. That’s because the phenethyl alcohol I’m smelling right now can only come from one thing, a rose plant. It makes me relax and think calm, peaceful thoughts. I wonder if I can take one of those roses with me so I can smell it all day in my house.” Well, that’s what my little voice says.
But, let’s take it further. Look at any garden center and you will see a huge variety of roses that you can purchase and plant in your yard. Somebody decided that lots of people would want to smell that fragrance, so, they took roots and saplings from a really nice-smelling rose plant and multiplied that plant all over the world. Now, more than any rose plant in the world, the continued existence of our rose plant is assured, thanks to us humans who fell for phenthyl alcohol and the information it conveys. And, it’s all because roses emit the information molecule phenthyl alcohol. Our rose will survive longer than you or me. I wish I emitted some phenthyl alcohol, then maybe somebody would find a way to keep me around longer. Then again, I would be very attractive to bees and, for humans, that’s a down side. I suppose I will have to find another way to survive.
Speaking of surviving, roses may enjoy a visit from a bee, but, its thorns certainly discourage visits from other creatures attracted by its smell, such as deer. What creature wants thorns lodged in their gums?
Flavors and fragrances are very powerful chemicals that affect us emotionally. They can stir our memories, make us feel good, or make us feel uncomfortable. In future blogs, I will describe more of the myriad ways they influence us.
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