Whip It Up!

Do you like lemon meringue pie? Did you know that the white meringue topping is made from egg whites? Making a meringue is an amazing trick. You start with a small amount of a clear, yellow liquid, and end up with huge mounds of fluffy white foam. This happens partly because of denaturation. The protein knots we talked about before can't withstand the beating, and they fall apart. But the whipping process also mixes a lot of air into the egg whites.

If you've never seen the changes egg whites undergo, it's a cool experiment to try. Take two eggs from the refrigerator, and separate the whites from the yolks while the eggs are cold (ask an adult for help). Make sure that there is absolutely no dark-yellow yolk mixed in with the whites. Then let the egg whites stand on the counter for about 30 minutes to warm up a little. Pour them into a large bowl made of glass, ceramic, copper, or stainless steel that has been carefully cleaned. Using either a hand whisk or a mixer (which is much easier), start beating the egg whites. Take a look at them every few minutes to observe what's happening.

First you'll notice that the egg whites form bubbles, although they're still yellow at this point. Then you'll notice that the liquid turns white, but is still thin and bubbly. Pretty soon, however, you'll notice that the egg whites become stiffer. If you lift the beaters out of the beaten egg whites, they form little peaks that bend over (this is called the soft-peak stage). But keep going! Eventually, you'll get stiff, shiny peaks that look like little snow-covered mountains (not surprisingly, this is known as the stiff-peak stage). At this point, you can even turn the bowl over, and the beaten egg whites won't come out. It's a pretty amazing transformation!

If you like to cook, you can sweeten the beaten egg whites with sugar, and bake them to make a kind of cookie called a meringue. You can even flavor the egg whites with things like chocolate or coconut. Do a Google search for a recipe!

Cran-tastic Sauce!

Do you like to eat cranberry sauce on Thanksgiving? Here's an easy recipe that also teaches you something about a molecule called pectin. Be sure to do this with an adult. But best of all, it's an experiment you can eat when you're done!

Pectin is a polysaccharide, a long-chain molecule that is made up of sugar units - a sugar chain. Pectin dissolves in water, but it thickens the liquid. It's what's commonly used to make jam and jelly thick and spreadable. Pectin is found in many fruits, such as cranberries.

What you'll need:
4 cups (1 pound) of fresh cranberries
2 cups sugar
1 1/2 cups water
Deep pan for cooking
Spoon with a long handle

Wash the cranberries, picking out any that aren't red, or any leaves or other bits of plants. Mix the water and sugar and boil. Keep heating over medium until the solution turns clear. Add the cranberries and turn up the heat to high. Make sure that your pan is deep enough that the cranberry sauce won't spatter out. Watch the berries as they cook, but don't get too close to the hot mixture! Keep stirring, and notice how the cranberry sauce feels. After about 5-10 minutes, the sauce will start to thicken up, and the pectin molecules dissolves out of the berries. Cook just a few minutes more, then let the sauce cool. Store in the refrigerator, then eat within a few days. Enjoy!

What's That Smell??

You've undoubtedly noticed that some vegetables are smellier than others. Corn, carrots, lettuce, green beans - they don't have much odor to them. But what about onions, garlic, and cabbage? Whew! These vegetables can make your eyes water, especially when they're cooking. Why does that happen?

All of these vegetables contain the element sulfur. In its pure form, sulfur is a light yellow powder that doesn't have much of an odor. But if you combine it with some carbon, hydrogen, and maybe a little oxygen and/or nitrogen, you can make some of the stinkiest molecules on earth! These molecules evaporate into the air easily, which is why you can smell them. The good part is that, when you cook these vegetables, the smelly sulfur-containing molecules leave. That means that they're pretty stinky while they're cooking, but that they taste much different (and often better) when they're done.

Try cooking some cabbage to check this out. Take a head of raw cabbage and cut it in half (have an adult help). Smell and taste both halves - they should be the same. Now cut one half into small pieces and place the leaves into a saucepan with 1 cup of water. Boil uncovered for 20 minutes. How does the cooking cabbage make the room smell? When the cabbage is done, remove a piece and let it cool. Compare its taste and smell to that of the uncooked half. What do you notice?

The kitchen got pretty smelly while the cabbage was cooking. That's because the sulfur-containing molecules left the leaves and went into the air. But the cooked cabbage tasted and smelled quite different from the uncooked cabbage because all or most of the stinky molecules had evaporated!

How to Cook Your Veggies

You know that you have to eat your vegetables, even though you may not like to. Did you know that how you cook vegetables affects how they look? Here's a simple experiment that you can do!

What You'll Need:
3 small, micowave-safe bowls
Measuring cup
Measuring spoons
Vinegar
Baking soda
Water
Microwave oven
Oven mitt
Spoon
Frozen green vegetable, such as peas

Pour 1/4 cup of water into each bowl. Add 1 tablespoon of vinegar to one bowl, and add 1 teaspoon of baking soda to another one. The third bowl should only have water in it. Add about 1/8 cup frozen vegetable pieces to each bowl (about 20 peas, if that's what you're using). Cook all three bowls in the microwave using high power for about 5 minutes. It doesn't matter whether you do them one at a time or all at once. When they're done, carefully remove the bowls from the microwave with the oven mitt. They will be very hot!!! Compare the vegetables - look at their color and mash them with a spoon to check their texture. What do you see?

You'll immediately notice that the vegetables cooked in vinegar (an acid) look grayish and very yucky. Who would want to eat them? The veggies cooked with baking soda (a base) look nice and green, but they are disgustingly mushy when you mash them with a spoon. Why do they turn out so different?

The green color is due to a molecule called chlorophyll, which has a magnesium (Mg) atom in the middle. Cooking in acid removes the magnesium and puts two hydrogens (H) in its place. The H-containing version of chlorophyll is a dull, ugly green color, and that's what you see. Cooking in a base doesn't remove the Mg, but it does break down the walls of the plant cells that keep the vegetable nice and firm. Without those strong walls, you can easily smoosh the cells together using a spoon. Vegetables cooked in water only keep a pretty good green color, and don't get mushy. Which one would you like to eat??

Denature An Egg!

Meat isn't the only protein-containing food that people commonly eat. Eggs are another good source of protein. In fact, the effect of denaturation are more obvious when you cook an egg than when you cook meat.

What's inside a raw egg? There's a dark yellow, liquid yolk floating in a light yellow liquid called the egg white. Now, what about a hard-boiled egg? The yolk turns light yellow, and the white becomes really white. Those changes occur because the heat from boiling denatures the proteins in the egg - exactly the same process that happens in meat.

Here's a pretty amazing way to denature the proteins in egg white without cooking them! Crack open an egg and separate the white from the yolk (you may need an adult to help with this). Put the white into a small bowl, and add some rubbing (isopropyl) alcohol to it. Pretty soon, you'll see white strings, which are denatured proteins. So, heating is only one way to mess up the protein knot - you can also do it simply by placing the proteins in an environment that they don't like.

Warning here: DO NOT EAT THE DENATURED EGG WHITE. YOU CAN POUR THE EGG/ALCOHOL MIXTURE DOWN THE DRAIN.

De-Nature of Proteins

We've talked about what meat is made of - muscle (apologies to any vegetarians reading this!). But what happens when you cook meat? Why does it look and taste so different?

Meat is mostly made up of water, fat, and proteins, which are very long molecules composed of building blocks called amino acids. You can think of a protein like a necklace, with the amino acids being the individual beads. Normally, these protein necklaces are coiled up in a very specific shape. But when they are heated, this shape falls apart, and they just become shapeless blobs - this process is called denaturation. Imagine a rope tied in a very complicated knot that somehow becomes untied and end up just as a pile of rope. When you cook meat, you denature the proteins, which has several effects:

• Denatured proteins are easier for our stomachs to digest
• Denatured proteins make meat firmer and not so slimy
• Denaturation disrupts the stringy muscle fibers, making the meat easier to chew
• Denaturation changes the color of meat from translucent to opaque

Cooking has other benefits, as well, since it kills bacteria and improves flavor. However, those aren't related to the denaturation process. So, how do you like your meat cooked - rare, or well-denatured??

Talking Turkey

The centerpiece of most people's Thanksgiving dinner is the turkey. Turkey is, of course, a kind of meat, by which we usually mean the muscle tissue of an animal - beef from cows, pork from pigs, veal from calves, turkey from turkey, etc. Meat is, in general, a very nutritious food because it contains a lot of the proteins we need to stay strong and healthy (although it is possible to get those proteins without eating meat).

You've probably noticed that turkey (and chicken) meat comes in two colors, which we call white and dark. But we never see "white" beef, or "dark" fish. Why not? The color difference is due to a chemical called myoglobin which stores oxygen. Darker meats contain more myoglobin than whiter meats, and muscles that get more exercise have more myoglobin. Cows walk around a lot finding grass to eat, so they get plenty of exercise, and all of their meat is dark. Turkeys, on the other hand, stand around in pens just waiting to get fed, and they rarely, if ever, fly. Their legs and thighs work hard, but their breast muscles, which control their wings, don't do very much. So, their leg and thigh meat is dark, but the breast is white!

Science in Your Kitchen

You may not think of your kitchen as a laboratory, but it is! You may not think of trying a new recipe as an experiment, but it is! This month, in honor of the Thanksgiving holiday in the U.S., we will explore some of the science behind cooking.