Thanksgiving food science: Five holiday flubs explained

Fear not. The USDA, the FDA, the Mayo Clinic, Iowa State University Extension and that supreme court of all things turkey — the Butterball Turkey Talk-Line — have all assured the public that a frozen turkey is even safer than a fresh one because it won’t drip contaminated juices all over your refrigerator and kitchen counter during or after defrosting.

If you want to try it, excellent directions can be found online.

Gallery

Thanksgiving recipes from the White House: First-family favorites like Laura Bush’s green beans or Mamie Eisenhower’s pumpkin pie add personality to the holiday spreads in America’s most famous home.

Video

Washington Post food editor Bonnie Benwick brings some tips of the trade to The Fold set and shows us how to bring our best mashed potatoes to the Thanksgiving table.

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How does it work? One might think that the first couple of hours in the oven defrost the turkey and the subsequent hours cook it. But that’s not the way it works. Instead, the heat slowly works its way in from all sides, leaving a trail of successive defrosting and roasting.

But why doesn’t the skin burn to a crisp after five hours in an oven at the recommended temperature of 325 degrees? Because the interior of the turkey is at such a low temperature, any heat absorbed by the skin from the oven’s hot air is conducted into the body at an especially rapid rate, so the skin stays relatively cool.

That’s a consequence of how heat moves through solids from Point A to an adjacent, cooler Point B. The bigger the difference in temperature between A and B, the faster the heat moves between them. It’s like putting a cup of hot coffee on a frozen steak: The heat of the coffee will warm the steak, but the steak also cools the coffee faster than if the cup was just sitting on the table.

In the turkey, this process repeats itself layer by layer as the heat penetrates into the turkey, thereby preventing any part from retaining its heat long enough to overcook.

But don’t try to speed things up with a higher oven temperature. That can indeed burn the skin and leave the cavity full of “snowball stuffing.”

Smooth gravy

Why does pan gravy so often turn out to be either greasy or lumpy?

Making good pan gravy from a meat or poultry roast is easy in theory — and just as easy to botch. Although the ingredients are few, they must be combined in the right proportions by volume: one part fat, one part flour (or thickener) and eight or more parts broth. Often, that will be two tablespoons each of fat and flour to each cup of broth. The fat contributes a smooth, unctuous mouth feel plus all those savory, fat-soluble flavors, while the broth adds water-soluble flavors and determines the ultimate amount of finished product. More broth yields more but thinner gravy.

The secrets of good gravy involve physics and chemistry. The physical challenge is getting all the drippings out of the pan and separating them into a fatty part and a watery part. The chemistry is that flour plus water makes a gluey paste, so they must be kept apart until ready for the thickening step. That trick is accomplished by coating the flour particles with a barrier of fat so the water can’t get to them.

First, the physics: The fat and juices have to be separated from each other, because the fat will need to be measured separately. Many recipes instruct us to skim off the fat in the pan with a spoon or ladle. Good luck with that. Spoons and ladles are usually deeper than the layer of fat in the pan, so it’s difficult to maneuver them in such a way that only the fat flows into them. You can’t get all the fat out, and that’s the primary cause of greasy gravy.