IOWA Alumni Magazine | April 2014
Cooking with Chemistry

As he wheels a supply cart into a UI Chemistry Building classroom, Professor Russell Larsen mentally confirms he's brought everything needed for the experiments in this freshman honors seminar. Liquid nitrogen—check. Beakers and mixing utensils—check. And, most important of all, sea salt, Hershey's chocolate syrup, and fresh strawberries.

This class takes the novel approach that the way to UI freshmen's minds is through their stomachs. Foods are complex mixtures of molecules governed and understood by chemical principles and processes—in Larsen's words "edible chemistry." So, "Molecular Gastronomy: Chemistry for Hungry Minds" uses familiar treats like chocolate syrup, cookies, and ice cream to introduce students to scientific concepts and theories.

Through experiments, assignments, and projects, these students investigate the connections between odors and molecular shapes, between flavors and chemical transformations, and between textures and physical changes. Using their taste buds and brain cells, they discover that science influences how they taste, smell, and perceive food. In the process, they realize that chemistry lurks in the most unexpected, everyday places.

Husband-and-wife team Russell and Sarah Larsen, who love to share their passion for food and cooking, co-teach the popular course. As they point out in the syllabus, "Food can not only be savored with the senses, but also enhanced through intellectual understanding."

To whet participants' appetites for such discoveries, the course begins with an experiment in "flavortripping." Students chew Miracle Frooties lozenges, wait about 30 minutes, and then bite into a lemon. Prepared to pucker up at the sour taste, they're amazed—and delighted—to realize instead that the fruit tastes like sweet lemonade.

The tropical fruit Synsepalum dulcificum or Miracle Berry, which is the main, freeze-dried ingredient in Miracle Frooties, provides this taste sensation. The fruit contains a glycoprotein called miraculin, which binds to the tongue's taste buds and activates the receptors that sense sweetness, producing an effect that lasts about an hour before saliva washes away the protein.

"Molecular Gastronomy" takes place at 12:30 p.m.—the perfect time for students suffering from a snack attack. In one session, the professors set out spoons loaded with powdery substances. When students pop them in their mouths, their expressions register surprise and glee as the dry substances transform into peanut butter or Nutella.

These undergrads have just experienced the marvels of maltodextrin, a polysaccharide made from starch (in this instance, tapioca) that's a common ingredient in many processed foods. Maltodextrin coats and encapsulates high-fat substances; when the students eat the mixture, the maltodextrin dissolves in their saliva and releases the peanut butter or Nutella from the powdery coating. Another week, the students perform what a Nobel Prize winner called "the most widely practiced chemical reaction in the world." When he spoke those words, chemist Jean-Marie Lehn was referring to the Maillard reaction—the browning of food that occurs when amino acids react with sugars at elevated temperatures.

The sequence of chemical reactions first reported in 1912 by the French chemist Louis-Camille Maillard happens every time someone roasts coffee, bakes bread, or grills a burger. Depending on variables like temperature, moisture, and the food used, the reaction can form thousands of compounds that produce appealing texture, aroma, appearance, and taste. On the downside, experts say that some compounds, like 2-5-hydroxymethylfurfural (HMF) and acrylamidein, are potential carcinogens.

"Food is great to use in experiments. We don't have to worry about chemical toxicity."
~Sarah Larsen

For their Maillard reaction experiment, students observe the appearance of pretzels dipped in various liquids of different pH, including plain water, traditional lye water, and a sugar mixture. They look at photographs of the pretzels taken at various stages during cooking, noting any variations, and then record how the different chemical solutions affected the final product. As they observe and draw conclusions, they're thinking like scientists.

Taylor Palensky, a human physiology and prephysician assistant major, says the class has deepened both her understanding and her curiosity about chemistry: "I think more critically in my chemistry class, asking the 'why' questions rather than just the 'what is it' questions."

Although open to all majors, "Molecular Gastronomy" requires at least a strong high school chemistry background. The professors don't spoonfeed information to these 16 students; instead, they encourage the undergrads to explore and make their own discoveries. One experiment, in which liquid nitrogen is heated in a microwave, was proposed by a class member who saw it on the Internet and wanted to try it in class.

Eagerly, the students gather around the microwave to observe what happens to plastic cups filled with water or liquid nitrogen. As expected, the water soon boils, but the nitrogen behaves exactly the same as it does at room temperature. Russ Larsen explains the science behind the phenomenon: as water molecules are polar, with a positive and negative end, they respond to the microwave's electromagnetic field by vibrating, moving apart, and boiling into gas. In contrast, as liquid nitrogen molecules are linear and nonpolar, the microwave's energy simply passes through them without any effect.

Liquid nitrogen proves a versatile ingredient, appearing in a few more experiments. When dipped in cups of the steaming nitrogen, marshmallows become crunchy on the outside. And, in one particularly popular session that the students offer to repeat every week, liquid nitrogen makes ice cream in seconds.

Gathered around a yellow stand mixer decorated with a Tigerhawk sticker, class members carefully pour liquid nitrogen from a plastic canister into a mixture of cream, milk, sugar, and vanilla. The sub-zero nitrogen freezes the mixture almost instantaneously, demonstrating the principle of phase changes. An integral part of any chemistry classes these students may take in the future, phase changes reflect the physical transition of matter from one state—solid, liquid, or gas—to another.

Sarah Larsen also uses this activity as part of her STEM (Science, Technology, Engineering, and Math) outreach program with local junior high pupils. "Food is great to use in experiments," she laughs. "We don't have to worry about chemical toxicity."

While "Molecular Gastronomy" is a chemistry—not a cooking—class, it does give participants the chance to face-off in a cook-off. In the Iron Chef Iowa session—listed on the syllabus as Fe26 CHe2f I53owa—students compete against each other to create the perfect spherified food (an edible sphere containing liquid). As in the Iron Chef television show, they're required to use a special ingredient. In this case, it's alginate—an "anionic polymer" in chemistry terms or a "thickening agent" in chef-speak. Made from seaweed, the substance binds with water at the molecular level to produce a gel that's widely used in the food, pharmaceutical, and textile printing industries. Here, it binds with a calcium solution to provide a casing for a mixture of fruit juices and Jello powder—an haute cuisine version of Fruit Gushers.

Like "Molecular Gastronomy's" other experiments, this one provides plenty of food for thought. These students are unlikely to become an Iron Chef, although some may pursue a scientific calling. Wherever they end up, their professors hope they'll remember how one UI science class transformed their understanding of their world—at the molecular level.

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