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As the fall semester wraps up, students around campus prepare to head home for the first time in months for Thanksgiving break. Like everything else, this Thanksgiving will be unlike any before. Public health officials are urging Americans to spend Thanksgiving with immediate family only, and most Americans expect to have smaller plans than years past. Still, grocery stores are preparing for high numbers of shoppers in the days preceding Thanksgiving; just last year, 46 million turkeys were bought in the U.S., and 75 percent of Americans plan to have a turkey of the same or equal size as last year. Once delivered to the kitchen, these birds are cut open, dressed, basted, roasted and served with an assortment of side dishes, like cranberry sauce, stuffing and pumpkin pie. As the main dish, a good turkey has the potential to immortalize a Thanksgiving, while a dry turkey can ruin it. How, then, can scientific ideas drawn from the chemical industry help you make your Thanksgiving the best it can be?
Many ideas for cooking are derived from chemical engineering. Daniel Lacks, the head of the Department of Chemical and Biomolecular Engineering, defines chemical engineering as “any kind of engineering where you change the chemical composition of the material.” Graduates within this department commonly work in industrial settings, producing chemicals or materials on an industrial scale. Case Western Reserve University produced 55 chemical engineers in 2019, and many of these graduates are currently designing processes to manufacture pharmaceuticals, food products, batteries and more from raw materials.
According to Lacks, chemical engineers are often compared incorrectly to chemists. While there are similarities, chemical engineers are more focused on the processes surrounding the chemistry and work to produce polymers, batteries or other products. Lacks states, “in chemical engineering, we’re more interested in optimizing the ways to [create these products], rather than just understanding their properties.”
Concepts of chemical engineering occur right in your kitchen on Thanksgiving––like how the oven traps moisture inside the skin of the turkey as it cooks. “[In cooking], combining ingredients and heating them can change the chemical composition,” Lacks says. By denaturing proteins in a turkey or linking together large molecules to increase the viscosity of gravy, you can relate your cooking to chemical engineering.
Complex chemical reactions begin the minute you place a turkey in the oven. As it warms, oily juices and liquids evaporate from the meat into the hot air, moving from a liquid to a gas state. These particles are quickly transported out of the oven under a flowing exhaust stream, creating a savory aroma in your kitchen as you prepare the other dishes. Within your oven, heat and mass from the turkey are pulled by invisible driving forces as the temperature of the turkey stabilizes and water moves to the drier air outside the meat.
If you’ve ever taken a turkey out of the oven too soon, the outside of the meat may be a rich brown color, but the inside could still be raw. Heat transfer depends on the surface area-to-volume ratio of the material: for example, if you cut a potato in quarters, the quarters will roast much faster than the whole potato. As Lacks says, “When you’re heating a turkey, you should be concerned with the size of the turkey. It’s important to cook it at a certain rate, so that the outside doesn’t burn while the inside is still thawing. For this, it’s necessary to understand time-dependent temperature distributions and heat transfer. The same theories are regularly applied in industry, to ensure that the temperatures in large reactors remain uniform.”
Heat transfer can also depend on the innate chemical properties and starting temperature.
Lacks explains that heat transfer also varies with the surroundings. For example, boiling a turkey would lead to a different quality of heat transfer. “You can use the principles of heat transfer to optimize your cooking . You can cook your food more quickly with a convection oven — “convection” means that the air is moving, and by moving the air carries heat more quickly to your food. Or you can ensure a very controlled rate of heat transfer with a double boiler. Here, the pot with your food sits inside a pot of boiling water — the temperature of boiling water remains exactly constant, which makes the heat transfer to your pot very well controlled” Lacks says.
Within our ovens, a phenomena called process control helps to maintain constant temperatures. Lacks uses the example of basting to describe process control. “Feedback control is used to keep the turkey moist. [If] you see that the turkey is getting too dry, you can baste it to keep it moist,” Lacks says. “This is feedback control, because you are using a sensor (your eyes) to measure a characteristic of your product (the dryness of the turkey), and then acting on this information (coating the turkey with liquid) to get this product characteristic closer to what you would like it to be.”
When you turn on an oven, its heating elements are turned on. As the temperature rises, a sensor constantly records that temperature, sending that information to the temperature controller. If the current temperature is too high, the heating elements shut off. If the temperature is too low, the heating elements turn on. This process reiterates, eventually achieving a certain set temperature. Process control is seen in refrigeration cycles and ovens, but it’s also used within the chemical industry to control complicated processes.
These phenomena in chemical engineering show that, even in the kitchen, you can engineer the chemical properties of your turkey. Perhaps you might try to buy a smaller turkey this year to roast your turkey quicker, or you might substitute tofurkey, which would have a higher water content. If your turkey’s not ending up like you expect, don’t worry; experimenting is part of the process.