The Science of Thanksgiving - STEM

As the days grow shorter, my mind (and, okay, my stomach) turns to thoughts of Thanksgiving dinner. Like many people, Thanksgiving is one of my favorite holidays. I think this is because it's relatively simple; the only requirement is cooking (usually) and eating (always!). Nice.

Thanksgiving is chock full of STEM. The technology associated with Thanksgiving is pretty obvious and includes stoves, microwaves, refrigerators, and if you're really ambitious, various recipe and cooking-friendly apps.

The cooking process itself is all science. Let's back up a bit...all food and drink are composed of atoms and molecules of chemicals. Humans must ingest chemicals to survive—because we are chemicals. A perfectly baked golden-brown turkey is chemicals. Mashed potatoes with gravy are chemicals. Even pumpkin pie a la mode is chemicals. Chemicals are delicious!

In popular parlance, cooking generally means applying heat to food; heat changes food. For example, the proteins in food become firmer when heat is applied. This is why the liquid interior of an egg gets hard when you boil it. This is why a well-done steak is tougher than a medium-rare steak. When heat is applied, starches tend to act like sponges, soaking up moisture and expanding in size, e.g. pasta noodles. Fats such as oils and butters generally liquefy under heat application. The fibers in fruit and vegetables like sweet potatoes soften and break down under heat application.

If you've ever made anything, like a cake, from scratch, you have done a chemistry experiment. You've taken a series of particular ingredients, combined them in specific amounts in the correct order, and then used heat or sometimes, cold, to create a final masterpiece. That's chemistry!

If you want to wow your friends and family around the Thanksgiving table, you could mention fancy terms like 'Maillard reaction' and 'pyrolysis.' The Maillard reaction is a chemical reaction between reducing sugars and amino acids that gives browned foods, like seared steaks and bread crusts, their delicious flavor. In this reaction, the amino acids and simple sugars are rearranged into rings and collections of rings that reflect light in such a way to look brown. Typically in this process, hundreds of different flavor compounds are created and each type of food has its own distinctive flavor compounds. The involvement of amino acids differentiates this reaction from similar processes like pyrolysis.

Pyrolysis is merely the thermochemical decomposition of organic material at elevated temperatures; carmelization would be an example of pyrolysis. To a nonchemist, however, Maillard browning and pyrolysis/caramelization may appear similar to the eyes and taste buds. But beware: pyrolysis is also known as burning; too much pyrolysis causes bitterness and possibly also carcinogens.

In contrast, boiled, poached, or steamed foods have totally different flavors because neither of these browning reactions have occurred. The latter cooking methods cook the food at temperatures above the boiling point of water, so the surfaces of the foods dehydrate.

Of course, the star of Thanksgiving dinner is usually the turkey. Meat is animal muscle, approximately 75 percent water, 20 percent protein, and 5 percent fat, with small amounts of carbohydrates, minerals, and acids. What really happens to meat when you cook it? A lot of the water content in the muscle fibers leaches out—which is why cooked meat is smaller than raw meat. The protein in meat, called myoglobin, stores oxygen in red blood cells. When heat is applied, the iron atoms in the protein lose an electron (oxidation) and this changes the color. Hence, raw turkey is pink and cooked turkey is white. Also the reason it's important to let cooked meat rest is: hot food keeps cooking for a short period after removing heat, and resting heat maximizes juiciness.

Yum. I'm ready for dinner now. Bring on those juicy chemicals!

Lesley L. Smith, Ph.D. has earned a plethora of degrees, including a M.S. and a Ph.D. in Elementary Particle Physics. In 2012, she added to her collection by completing her MFA in Writing Popular Fiction at Seton Hill University. Dr. Smith’s short science fiction has been published in several venues, such as "Analog Science Fiction and Fact," "Daily Science Fiction," and Nano Meets Macro. She is an active member of the Science Fiction/Fantasy Writers of America (SFWA) and Rocky Mountain Fiction Writers (RMFW), and is also the founder and editor of Electric Spec.

Dr. Smith has held a variety of scientific jobs, including investigating quarks, dark matter, extrasolar planets, clouds, atmospheric chemistry, and global warming. She has worked for a variety of research institutions, while her nonfiction articles have been published in venues that include the Physical Review and Modern Physics Letters. She is a long-time member of the The American Physical Society (APS) and The American Geophysical Union (AGU).

For more information, connect with Dr. Smith on her website

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