A bowl of potatoes with steam coming off of them, with a hand masher propped on the side

Perfectly browned rolls? Fluffy mashed potatoes? Chemistry in the kitchen makes for delicious Thanksgiving dinner dishes

The containers may be pots instead of beakers, and the heat source a gas stove burner rather than a Bunsen burner, but make no mistake -- chemistry is at the heart of preparing food for Thanksgiving dinner.

From the browning of rolls to perfecting cranberry sauce to achieving the optimal consistency of mashed potatoes (which means enduring some lumps), Jessica VandenPlas, associate professor of chemistry, explains the chemistry behind how the foods become delicious as well as the reasons some dishes might not turn out as planned.

And yes, she has thoughts on the tryptophan-as-sleep-inducer notion, too. (It is an amino acid, after all).

VandenPlas shared her insights at GVSU's monthly Science on Tap gathering at the SpeakEZ Lounge, where experts host discussions on current scientific topics over food and beverages in a casual setting.

Here is what she discussed, along with a bonus section on mashed potatoes.


Several rolls on a baking dish

"Dough is disgusting, but bread is amazing," VandenPlas said.

We can thank chemistry for the amazing -- but only if the preparation is done with care, said VandenPlas, who likened the controlled principles of baking to the controlled principles of a chemistry experiment.

"With baking, you have to be really precise," she said. "You have to use the exact ratios, in a particular order and with the temperatures perfect, and if anything goes wrong the experiment fails, just like in the lab."

For instance, VandenPlas said, the reason you must mix the dough only until ingredients are combined is because stirring too much causes the carbon dioxide to escape before baking. When carbon dioxide optimally escapes during baking -- brought on by acids and bases reacting to each other -- you get light and fluffy rolls.

Now for the really amazing: The browned, nutty flavor of rolls is due to the Maillard Reaction. It is a reaction between sugar and protein, and it not only explains browned baked goods but also seared steaks -- and browned turkeys, VandenPlas said.

Cranberry sauce

The ingredients are simple: Water, sugar and cranberries. But the molecular structure of the pectin in cranberries explains some of the chemistry in the process toward reaching the sauce's gel-like quality, VandenPlas said.

Pectin is a long chain of sugars in cranberries. As the cranberries are heated and start to pop, and you macerate them with a spoon, the cells open and those long chains tangle, creating the firm, gel-like structure, she said.

Mashed Potatoes

A bowl of potatoes with a hand masher

Your goal for good mashed potatoes means avoiding the molecular tangles that are favorable for cranberry sauce, VandenPlas said. Otherwise, you risk gummy potatoes.

"It seems so simple: Boil potatoes, mash potatoes, eat potatoes," she said. But again, the cellular level of the plant has implications for the right consistency.

In this case, you want a leucoplast, which VandenPlas described as a little packet of starch, to release just enough starch but not the starch's long molecular chain.

The key is to reduce agitation. That means carefully heating them -- she noted one food scientist recommends a two-step, low-and-slow cooking process -- and keep the potatoes out of the mixer for the last process.

Mash them with a fork or hand masher, she said. And embrace lumps to avoid gummy potatoes.

Pumpkin pie

A pie crush, a pumpkin pie, a measuring spoon filled with nutmeg and beaters with pie filling on a counter with flour scattered

The interesting chemistry here is how similar two of the spices used in pie are almost identical at the molecular level, but for one divergence that gave us distinct flavors and aromas.

Cloves (eugenol) and nutmeg (isoeugenol) have flavoring molecules that are almost the exact same molecular structure, but the placement of one stronger, double bond for eugenol creates the smell and taste of cloves, VandenPlas said.

And finally, the turkey (and about that tryptophan)

We already know that the Maillard Reaction browns and flavors the turkey. As for another trendy way to improve flavor, brining, chemistry is a key factor in its effectiveness, specifically osmosis.

The brining fluid contains many spices, sugar and crucially for this discussion, lots of salt. Osmosis goes into effect, trying to create an equilibrium amid the floating salt ions by initially sucking the water out of the turkey, VandenPlas said.

This reaction explains why you can't shortcut the brining process, she said. If you fail to brine it long enough, you end up with a dry and salty turkey. But if you brine it for at least eight hours, eventually through osmosis equilibrium is achieved and water returns to the turkey, making it moist and flavorful.

But don't blame the turkey, specifically the tryptophan, for post-dinner sleepiness, she said. In theory, the amino acid creates a reaction that eventually leads to the production of melatonin, a chemical that makes you sleepy.

In reality, however, tryptophan is one of many amino acids competing for passage to the blood-brain barrier after the meal, and ultimately doesn't doesn't get there in a high enough concentration to affect sleepiness, VandenPlas said. Also of note: Tryptophan is in a wide variety of foods, including other meats, eggs and cheese, not just turkey.

What is more likely the culprit for post-dinner nap time? The potatoes, and stuffing, and rolls, and pie, and the many other carbohydrates consumed with this meal with simpler molecular structures that can more quickly affect the body, VandenPlas said.

Another likely factor is the consumption itself. You're taking in a day's worth of calories (or more) in a short amount of time, she said. That influx has consequences.

"Digestion takes a lot of energy. That's going to make you feel sleepy," she said. "Your body is saying, 'Oh no, I've got a lot of work to do.'"

A closeup of fingers sprinkling nutmeg on a pumpkin pie


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