A Moment of Science

Talking Turkey

Turkey LegRecently, there was a national performance art event open to participation by anyone. Did you take part? I mean the national simultaneous turkey-eating event. If you missed it, there's another one coming up ?

But what do most of us really know about turkeys? Besides that Benjamin Franklin thought this bird would make a great national symbol? Franklin is often ridiculed for that idea, but, who knows, it might have made our nation more reluctant to become involved in wars.

There is science in turkey-eating in that it involves the biochemical process of digestion, beginning with mastication. Oh, yes, don't be embarrassed ? I know that you masticate your food! Don't worry. Pretty much everybody does it.

L-TryptophanSom/1e of us have heard that tryptophan in turkey makes us sleepy. In fact, lots of foods have more tryptophan than turkey. What pushes tryptophan into your brain is a carbohydrate load, not the tryptophan in a meal.

But the chemistry starts before that. For cooking is chemistry: it involves the coagulation of proteins and the partial oxidation of proteins, fats and carbohydrates (sugars). And yet — the devil is always in the details, because a turkey is made of two kinds of meats: the white and the dark. The white meat is perfectly cooked at about 155° C while the dark meat needs to be at about 165° C. If you like the dark meat you may have noticed that it's often undercooked. Or, if it's not, the breast meat tends to be overcooked and dry. What to do? One solution is to ice the turkey breast for awhile before putting the bird in the oven. Putting foil on the breast probably won't help, although it can keep it from overbrowning there.

The Maillard ReactionMuch of the wonderful aroma of cooking turkey — and other meats — comes from chemical reactions between proteins and carbohydrates known as Maillard reactions. In fact, this class of reactions is responsible for producing a wide variety of flavors in all kinds of foods and beverages. Some of its products are also carcinogenic.

The Australian brush turkey, Alectura lathami, is one of 21 species of birds known as megapodes. These birds are unique in that they do not incubate their eggs. Instead, they lay their eggs in rotting leaves and leave the heat from the compost to incubate them. The chicks are also superprecocious — able to function pretty much as adults as soon as they're hatched. But this creates in turn a unique situation in that, when the eggs hatch out, the young chicks cannot "imprint" on a parent or any other member of its species. How would you figure out what you are if you came into the world under such circumstances?

Australian Brush TurkeyBehavioral ecologists in Sydney, Australia have been studying the problem and have found, so far, that brush turkey chicks are more interested in turkey-mannikins that peck than ones that are motionless or only turn from side to side. Removing ultraviolet illumination eliminated even that interest, so the birds are somehow programmed to recognize patterns and/or color.

Turkeys have also proven useful as test subjects. Harvard scientists in the 1990's put micro-strain gauges and used sonomicrometry — a way to measure small distances — within the leg muscles of turkeys to study the biomechanics of running in these animals. They found that the main function of the muscles while running was to simply generate adequate force to support the animal while letting the elastic energy in the other tissues — chiefly the tendons — do the work.

Finally, did you know that turkeys can be cross-bred with pheasants? As with mules, hybrids of horses and donkeys, these birds are sterile. But what do they taste like?