Read Online What the Nose Knows: The Science of Scent in Everyday Life by Avery Gilbert - Free Book Online
Book: What the Nose Knows: The Science of Scent in Everyday Life by Avery Gilbert
Read Free Book Online
Authors: Avery Gilbert
Ads: Link
link to
cis
-rose oxide and you see that this molecule is also responsible for the floral quality of fresh lychee fruit. On the lychee fruit home page you find that another potent odor is 1-octen-3-ol; clicking on it takes you to the Brittany oyster home page. Why? Because 1-octen-3-ol lends an earthy odor to both French oysters and lychee.
Is there a profound meaning in the hyperlink path from oysters to spoiled chicken to feces to Gewürztraminer to lychee and back? I doubt it. It’s just Six Degrees of Kevin Bacon played with molecules. The olfactory web of 4-mercapto-4-methylpentan-2-one that links green tea to peony is not unusual. A given odor molecule turns up time and again; nature is economical and uses the same molecule different ways in different organisms.
B Y 1974, ROUGHLY 2,600 volatiles had been identified in food. By 1997 the estimate had swelled to 8,000 and was predicted to climb eventually to 10,000. These are large numbers. They would be even larger if we included volatiles from nonfood items like airplane glue, dirty socks, and that crust of dried vomit under the backseat of the family minivan. Add them all up and the numbers are overwhelming. When it comes to potential smells, nature’s bounty seems infinite.
What does all this molecular variety mean for the sense of smell? If the same chemicals turn up repeatedly as key smell ingredients, what impact does the rest of nature’s chemical diversity have on the human nose? One answer is that we are missing most of it: we read the olfactory headlines and ignore the fine print. The field of sensory analysis confirms that only a fraction of the chemicals entering our noses from a given source make a difference to our perception of its odor. In most foods, for example, only a few of the volatiles detected by chemical analysis are present at nose-perceptible concentrations. Of the 400 or more volatiles found in a tomato, for example, only sixteen reach the threshold of human perception. One expert figures that fewer than 5 percent of the volatiles in a food actually contribute to its aroma. Perhaps odorants aren’t as numerous as they seem.
So-called aroma models take this insight even further. To create an aroma model for french fries, for example, scientists run a batch through the GC/MS and generate a complete list of all the volatiles. Their goal is to create a fully realistic french-fry aroma using as few of the volatiles as possible. They begin by selecting odorants present at concentrations well above our sensory threshold. If a blend of those doesn’t match the original aroma, they extend the list to include odorants at or below the sensory threshold. Once a blend closely matches the full aroma, it is tested further. One by one, odorants are subtracted from the formula. If the resulting formula smells less realistic, the subtracted odorant is restored. If the subtraction makes no difference, that odorant is dropped. The final aroma model is one of irreducible simplicity—a stripped-down formula that smells complete to the nose. An authentic french-fry smell, for example, can be made from nineteen ingredients. This includes a trace of stinky methyl mercaptan—without it, the formula lacks the necessary boiled-potato character.
Aroma models have been developed for Swiss cheese, Camembert, basil, olive oil, and baguette crust, among other things. These whittled-down formulas all point to the same conclusion—most volatiles in a food add nothing to its smell. A high-fidelity odor replica can be created from one or two dozen ingredients. A classic example is the cup of coffee. Chemists have been analyzing coffee aroma for more than 100 years and have found more than 800 different molecules. Using aroma models, German scientists found a mere twenty-seven high-impact molecules in medium-roasted Arabica coffee; they made a high-fidelity model using only sixteen of them.
The sensory logic of aroma models can be extended to nonfood areas, and may
cis
-rose oxide and you see that this molecule is also responsible for the floral quality of fresh lychee fruit. On the lychee fruit home page you find that another potent odor is 1-octen-3-ol; clicking on it takes you to the Brittany oyster home page. Why? Because 1-octen-3-ol lends an earthy odor to both French oysters and lychee.
Is there a profound meaning in the hyperlink path from oysters to spoiled chicken to feces to Gewürztraminer to lychee and back? I doubt it. It’s just Six Degrees of Kevin Bacon played with molecules. The olfactory web of 4-mercapto-4-methylpentan-2-one that links green tea to peony is not unusual. A given odor molecule turns up time and again; nature is economical and uses the same molecule different ways in different organisms.
B Y 1974, ROUGHLY 2,600 volatiles had been identified in food. By 1997 the estimate had swelled to 8,000 and was predicted to climb eventually to 10,000. These are large numbers. They would be even larger if we included volatiles from nonfood items like airplane glue, dirty socks, and that crust of dried vomit under the backseat of the family minivan. Add them all up and the numbers are overwhelming. When it comes to potential smells, nature’s bounty seems infinite.
What does all this molecular variety mean for the sense of smell? If the same chemicals turn up repeatedly as key smell ingredients, what impact does the rest of nature’s chemical diversity have on the human nose? One answer is that we are missing most of it: we read the olfactory headlines and ignore the fine print. The field of sensory analysis confirms that only a fraction of the chemicals entering our noses from a given source make a difference to our perception of its odor. In most foods, for example, only a few of the volatiles detected by chemical analysis are present at nose-perceptible concentrations. Of the 400 or more volatiles found in a tomato, for example, only sixteen reach the threshold of human perception. One expert figures that fewer than 5 percent of the volatiles in a food actually contribute to its aroma. Perhaps odorants aren’t as numerous as they seem.
So-called aroma models take this insight even further. To create an aroma model for french fries, for example, scientists run a batch through the GC/MS and generate a complete list of all the volatiles. Their goal is to create a fully realistic french-fry aroma using as few of the volatiles as possible. They begin by selecting odorants present at concentrations well above our sensory threshold. If a blend of those doesn’t match the original aroma, they extend the list to include odorants at or below the sensory threshold. Once a blend closely matches the full aroma, it is tested further. One by one, odorants are subtracted from the formula. If the resulting formula smells less realistic, the subtracted odorant is restored. If the subtraction makes no difference, that odorant is dropped. The final aroma model is one of irreducible simplicity—a stripped-down formula that smells complete to the nose. An authentic french-fry smell, for example, can be made from nineteen ingredients. This includes a trace of stinky methyl mercaptan—without it, the formula lacks the necessary boiled-potato character.
Aroma models have been developed for Swiss cheese, Camembert, basil, olive oil, and baguette crust, among other things. These whittled-down formulas all point to the same conclusion—most volatiles in a food add nothing to its smell. A high-fidelity odor replica can be created from one or two dozen ingredients. A classic example is the cup of coffee. Chemists have been analyzing coffee aroma for more than 100 years and have found more than 800 different molecules. Using aroma models, German scientists found a mere twenty-seven high-impact molecules in medium-roasted Arabica coffee; they made a high-fidelity model using only sixteen of them.
The sensory logic of aroma models can be extended to nonfood areas, and may
Similar Books
