Cocktail Party Physics

Cocktail Party Physics

Physics With a Twist

A Taste of Science for Turkey Day


It's Thanksgiving, and the Time Lord and I have repaired to Las Vegas for our annual holiday tradition of poker, spa treatments, shopping, and dining -- including the obligatory Thai meal at Lotus of Siam. (Yeah, okay, mostly I hole up in the room and write whatever fun stuff I never have time to work on normally. Color me a workaholic.)

But let's jump into the WayBack Machine to my salad days as a young 20-something freshly arrived in New York City. It was the first Thanksgiving away from family not just for me, but several of my fellow transplants. We decided to make our very own traditional Thanksgiving meal, complete with candied yams, pumpkin pie, and a delicious roast turkey.

There was just one catch: none of us had ever cooked a turkey before. And at the time, Google did not exist. (Gasp! I know, right?) But really, how hard could it be? Famous last words. This is what our combined efforts to cook that darned turkey looked like after just the first hour:

We ended up ordering Chinese (actually something of a NYC tradition for both Thanksgiving and Christmas). Perhaps you, too, are facing the challenge of preparing a full traditional Thanksgiving dinner, and you're still haunted by the disastrous attempts of yesteryear. Fear not! Science can help answer the pressing question of how best to cook a turkey to achieve the highest degree of yumminess.

For instance, celebrity chef Alton Brown has his own unique approach to turkey preparation: deep fry the sucker! All you need is a big enough vat of grease, and a special contraption to ensure you can lower the entire turkey into the vat from a safe distance. This is particularly critical if said turkey happens to be frozen at the time. When Brown did this for his TV show, fire ensued. But it did result (eventually) in a delicious meal. Here's Brown recapping that experiment for a rapt audience at Google:

That's one spectacular method of turkey preparation, but it's not for everyone -- certainly William Shatner loves his, but advocates safety first.

Most of us prefer the standard gas or electric oven method. But even then, there are some science-based secrets to bringing out the best in your bird. Brown mentions brining at the start of his video. It just so happens that brining is key to a moist, succulent bird (it's less critical for the Tofurkey favored by your local vegetarian). A couple of years ago, physicist Diandra Leslie Pelecky (a former co-blogger) put together a nice little video about salts and the underlying science of brining:

Diandra also included the following tips:

If you're going to try brining, I recommend the original Martha Stewart recipe that got me started. The ingredients sound a little odd, but believe me, they turn out a really tasty bird. Pay attention to the concentration of salt and sugar in the water, though!

One hint I forgot to add in the video: It's really important to let the brine cool before you dunk in your birds, so I like to use about 1/4 of the water to heat and dissolve the salt/sugar in, and then make up the other 3/4 of the water with ice, so the liquid cools down and you can start with the brining faster.

I recommend the scanning electron micrograph images at the Internet Microscope for Schools site for looking at the different types of salt a little closer.The Salt Institute, for everything else you ever wanted to know about salt.

Okay, so you've got the whole brining thing down. How long do you actually cook the turkey? Symmetry Breaking suggests you use (I kid you not) this equation from SLAC Director Emeritus Pief Panofsky: t = W(2/3)/1.5, where t is the cooking time in hours and W is the weight of the stuffed turkey, in pounds. "The constant 1.5 was determined empirically," Symmetry Breaking claims, and also adds this intriguing bit of trivia:

The food industry uses particle accelerators to produce the sturdy, heat-shrinkable film that Butterballs come wrapped in. When a beam of electrons from a particle accelerator hits the plastic wrapping, it causes a chemical reaction that makes the film super strong and heat resistant. The food industry purchases the treated shrink wrap from plastic manufacturers in the form of bags or rolls. A turkey gets placed inside, and voila, a fresh meal will soon grace your Thanksgiving table.

All this assumes you're using a conventional oven, of course. Cooking for Geeks offers an intriguing option: hacking a slow cooker to prepare a turkey sous vide. Sous vide cooking is basically slow cooking at lower than usual temperatures over an extended period of time, in a vacuum. Foods are seasoned, sealed in vacuum pouches, and slowly heated in a water bath whose temperature is well below boiling, often for around 24 hours.

Maybe you're just not game for hacking a slow cooker this holiday. Or perhaps you're intrigued by the notion of a more environmentally friendly means of turkey preparation. If you have world enough and time, live in a region with copious sunlight, there's always solar cookers. There's different models, and the maximum temperatures attainable in the kind of cooker you have varies a bit.

A single-reflector solar cooker, for instance, has top temperatures of about 300 degrees F, although food usually cooks just fine at temperatures in the 200 degree F range, according to the fine folks at Solar Cooking. The higher temperatures just mean you can cook more food a little faster. The nice thing about slower cooking in a single-reflector box is that the food won't burn after it's done, so you can put the food in, go about your day, and come back when you're ready to eat and find it done and kept nicely warm for your consumption. It's like a sunlight-powered crockpot.

A more patient, thinking-ahead approach is probably a good idea, since it takes, in general, twice as long to cook something in a solar cooker than it takes in a conventional oven. Just make sure you haven't inadvertently bought a parabolic cooker. The parabolic shape is great at focusing sunlight, hence the legend about how Archimedes used an array of mirrors in the shape of a parabola to set fire to invading Roman ships intent on conquering Syracuse. (As brilliant as Archimedes was, when the Mythbusters and a team from MIT tried this, it proved incredibly difficult.) So food cooked in a parabolic solar cooker might cook faster, but needs to be stirred and watched carefully. Which kind of defeats the purpose of just being able to put the food items in and walk away.

My personal favorite recipe for turkey preparation can be found on Cooking for Engineers: Smoked Beer Can Turkey. Our engineer chef adapted the recipe from a similar one for chicken, although a turkey is a much larger bird, and hence a standard 12-oz beer can wouldn't suffice. What does work is a "24-oz microkeg shaped can of Heineken."

There's a bunch of preparatory steps outlined in the recipe, but the idea is that inserting a beer can into the turkey's derriere provides flavored steam to the inside of the bird as it cooks, keeping it moist and delicious.

Our friendly cooking engineer is skeptical that the beer adds flavor to the meat during the cooking process: "If the beer is giving off steam, then most of that steam is just going to be water... most of the beer flavor will just be concentrating in the can." Nonetheless, he included the beer, along with some crushed herbs (six chopped bay leaves and two teaspoons of dried thyme), because hey, it's all about the principle of the thing. (Emeril, BTW, has demonstrated beer-brined chicken on his cooking show, which combines beer-can chicken with the brining process, and in that case the beer really does impart flavor to the bird.)

So there you have it: some fine science to help you prepare the best Thanksgiving turkey you can -- or at least have a lot of fun during the preparation process. And if you feel incredibly sleepy after said feast, don't blame the tryptophan. This is an amino acid present in turkey (and various other meats and proteins) that allegedly causes drowsiness because the body uses it to make seratonin, a neutrotransmitter that has been experimentally shown to put flies to sleep.

All of which is true as far as it goes, but the reality is a bit more complicated than that. See, tryptophan is just one of several amino acids found in turkey and other protein-rich foods, all of which are competing for the shame "shuttles" (special transport proteins) for transport beyond the blood-brain barrier. Tryptophan isn't even the most abundant of those amino acids, so the likelihood of a significant amount of the stuff getting to your brain and making you sleepy by increasing serotonin levels are pretty slim.

Unless -- you happen to follow the turkey with a nice helping of pumpkin pie, liquid nitrogen ice cream and a hefty dollop of fresh whipped cream. A massive infusion of carbohydrates also increases serotonin in the brain, without any need for tryptophan. Dessert causes the pancreas to secrete more insulin, which helps the body's tissues absorb glucose and most amino acids -- but not tryptophan.

This has the effect of winnowing out the competition for those protein transports to the brain, meaning more tryptophan is likely to get there, increase the synthesis and serotonin, and voila! You fall into a satisfied state of drowsiness. At which point, you may as well give in and relax with a dose of The Muppet Show. Happy Thanksgiving, everyone!

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

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