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Food Matters

Food Matters

Giving science a seat at the table

Pumpkin, hold the spice

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Feel that chill in the air? Must be Fall, and with the change in seasons comes the latest food craze: pumpkin spice.

Image courtesy of Pam Ronald / UC-Davis

Now, I’m hardly the first person to notice this. The New York Times, the Wall Street Journal, and Salon have all recently weighed in on the growing flavor mania.*

Alas, most pieces set pumpkin-flavored goodies up as a paper tiger, only to knock down how aromatic spices such as cinnamon, nutmeg, cardamom, allspice, anise, ginger, mace, vanilla, or cloves are truly responsible for their comforting scents (if you’d like to know a little bit more about the similarities between some of these spices, check out this NBC Learn animation).

So, warm spices aside, I wondered: what does pumpkin smell like, all by itself?

You probably know pumpkin (genus Cucurbita), a gourd with dense orange-yellow flesh and a hard outside rind, for its traditional role in pies. With fibers and sugars similar to those in sweet potatoes, pumpkin finds itself roasted, stewed, or used as a starter starch for a variety of autumn ales.

When I first started digging into the literature to find pumpkins’ native scents, I figured they’d contain mostly 9-carbon alcohols called nonanols - I worked with similar compounds in graduate school, and my colleagues dubbed me “Mr. Pumpkin” for an entire month. Researchers at General Foods Corp. (NY) authored this 1981 American Chemical Society symposium series, indicating that other Cucurbita, like the muskmelon and cucumber, exude high levels of volatile nonane compounds. Did pumpkins play along? To explore further, the scientists extracted and distilled the flavors from both fresh and canned fruit.

Let’s talk about six

For pumpkins, shorter chains apparently rule the day. When you first slice into one, note the clingy, vegetal odor. That’s major aroma constituent cis-3-hexenol, a six-carbon compound also known as ‘leaf alcohol.' Close chemical cousins n-hexanol and 2-hexenal round out the top 3 smells, according to the authors. Notice a buttery undertone? Diacetyl, the flavor behind movie-theater butter (and the industrial medical condition “popcorn lung”) occurs naturally in pumpkin. So does pyridine, a common laboratory solvent usually associated with lingering fishy smells.

Clockwise, from top left: cis-3-hexenol, diacetyl, 2-methylbutanal, furfural, pyridine

Interestingly, the profile completely changes when we consider pumpkin puree, the canned orange pulp often used as a pie base. Due to heat processing, the flavor palette now includes a malty, burnt note from 2-methyl-butanal, along with much more pyridine odor and furfural, a sugar decomposition product smelling of grain and sawdust. The authors note that "virtually all of the six-carbon aldehydes and alcohols...have been lost." Canned pumpkin flavor tastes markedly different from the fresh stuff.

Source: Parliment et. al., ACS Symposium Series 1981, (11), p. 129

Does either of these flavor profiles match the “spice” flavoring on that latte? Probably not. In fact, just last month the Boston Business Journal coaxed a flavor chemist into confessing that the vaunted Starbucks pumpkin spice latte likely contained no actual pumpkin flavor. Good luck getting them to admit anything more; fragrance-makers carefully guard their formulations as trade secrets.

Readers, can you smell any “real” pumpkin in the multitude of new pumpkin spice food products? If anyone with a keen nose (or a gas chromatograph) wants to try, I’d be interested to know.

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*Here’s a partial list of all the pumpkin spice-flavored items I came across while researching this post: waffles, lattes, teas, bagels, e-cigarettes, donuts, coffees, K-cups, air fresheners, muffins, toaster pastries, potato chips, M&Ms, cookies, hot chocolate, steaks, soy milk, soups, beer, ice cream, cream cheese, butter, pancakes, milkshakes, yogurt, marshmallows, vodka, dog food, egg nog, granola, milk, breads, whiskey, biscotti, cereal, cheesecake, creamers, crepes, syrups, salsa, and (of course)…pie.

The views expressed are those of the author and are not necessarily those of Scientific American.

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