In this issue:
- Egg in a Bottle Project
- Green Eggs & Ham Project
- Baked Alaska
- Fabulous Facts
- Science Links
Science applies to almost all of life, even to cooking and eating. Chemical reactions and changes are happening all the time in the kitchen, from bread rising to sauce thickening. Do the following projects to explore the fascinating properties of eggs and have some fun with science you can eat!
Egg in a Bottle
Learn about the relation of temperature to pressure as you watch an egg get sucked into a bottle. This project requires adult supervision.
>> Watch our video demonstration, and then try it yourself!
What You Need:
- Saucepan and stove
- Wide-mouth glass drink bottle (such as a Starbucks Frappuccino bottle – the mouth needs to be a little smaller than the egg. We used a large egg wih the Starbucks bottle, but with other bottles you might need smaller eggs.)
- Strips of paper folded a couple times length-wise (slightly shorter than the bottle)
What You Do:
- Place the eggs in a saucepan and add enough water so that the eggs are covered by about an inch. Let the water boil for 5 minutes, then remove the pan from the heat and cover it. Let it sit for 25 minutes, then remove the eggs and dip them in cold water.
- Peel one of the eggs, then dip it in water and set it with the small end down in the mouth of the glass bottle. It should be slightly larger than the mouth of the bottle, so it doesn’t fit inside.
- Use a match to light the end of a strip of paper on fire. Lift the egg off the bottle, drop the paper inside with the flame down, and quickly replace the egg. Watch the egg wiggle a little in the bottle mouth, and then get sucked inside!
First, the science behind a hard-boiled egg: Egg whites are made of water and proteins. Proteins are made of long chains of amino acids, but in an egg the chains are clumped tightly together in individual spheres. (These are called “globular proteins.”) When the egg is heated, the proteins and water molecules begin to move faster. As they move and collide with each other, the individual protein chains start to “unravel,” eventually bonding loosely with other protein chains, forming a network of protein with water trapped inside. The consistency has changed from runny egg white to a soft solid!
So how does this squishy-but-solid egg get mysteriously pushed inside the bottle? The answer is all about air pressure. When you first set the egg on the bottle, the air pressure inside the bottle matched the air pressure outside, so nothing happened. When you dropped the burning paper into the bottle, it caused the air inside to heat up and expand rapidly. That expanding air pushed the egg aside and escaped from the bottle; that’s why you saw the egg vibrating. When the fire consumed all the oxygen inside the bottle, the flame went out and the remaining air in the bottle cooled down. Cool air takes up less space, exerting less pressure inside the bottle. (The egg acted as a seal to prevent outside air from getting in to fill the extra space.) The result was an unbalanced force—the force of the air pushing on the egg from outside the bottle was greater than the force of the air pushing up on it from inside the bottle. Voila – the egg was pushed into the bottle!
How do you get the egg out again? You need to increase the pressure inside the bottle. Turn the bottle upside down and tilt it until the small end of the egg is sitting in the mouth. Now put your mouth close to the bottle and blow, forcing more air into the bottle and raising the pressure inside. When you take your mouth away, the egg should pop out – just be careful it doesn’t hit you in the face!
Green Eggs & Ham
When you were little, you probably read the Dr. Seuss book Green Eggs & Ham. Here’s a little pH trick to make some green eggs just like in the book.
What You Need:
- Frying pan and stove
- Red cabbage (it’s called red, but it looks purple!)
What You Do:
- Chop a 1/2 cup of cabbage, cover it with boiling water, and let it sit for 10 minutes until the water is dark purple. Strain out the cabbage.
- Crack an egg and separate the egg white from the yolk by carefully pouring the egg from one half of the shell to the other over a bowl. (Or you can pour the egg into a slotted spoon over a bowl instead.) Set the yolk aside.
- Mix a little cabbage juice in with the egg white. What happens?
- Grease the pan and let it heat up a little, then pour the egg white in.
- Set the yolk in the middle of the egg white and finish cooking!
Red cabbage contains pigments called anthocyanins, which change colors when they come in contact with acids (low pH) or bases (high pH), making them a natural pH indicator. When the cabbage juice comes in contact with an acid (like vinegar) it will turn red, but when it is mixed with a base it will turn bluish-green. What does this project tell us about egg whites, then? Egg whites are basic (also called alkaline) and so they turn the red cabbage juice green.
Fizz Wizard & Jammin’ Jelly Kit
This fun kit introduces basic chemistry concepts through making incredible and tasty concoctions like soda pop and pudding. The chemicals are all food-safe, so you can eat the experiments when you’re done! In the process, learn about pH levels and polymers, concentration of solutions, and chemical reactions. The instructions explain the science behind these 16 fun experiments. Some household items are required, such as sugar, lemon juice, and milk. Ages 8 & up.
Is it possible to put ice cream in a hot oven without it melting? Oh, yes! Make this delicious dessert to try it out. There are many variations of this dessert—choose the type of cake, ice cream, fillings, and toppings that you like best. You can make one large dessert, or individual ones as we did.
- Cake or brownie mix
- Ice cream (flavor of your choice)
- 4 egg whites*
- 1/4 tsp cream of tartar
- 1/2 cup sugar
*Safety note: Sometimes the egg whites in the meringue won’t be fully cooked. If you’re concerned about salmonella, use pasteurized dehydrated egg whites or meringue powder you can buy at the store. You can also use liquid pasteurized egg whites from a carton, although the meringue won’t fluff up as much as with fresh eggs.
What You Do:
- Choose a bowl (or individual ramekins) for an ice cream mold and line it with aluminum foil. Pack the ice cream in tightly and then freeze for several hours or overnight.
- Bake the cake or brownie mix as directed on the package. Allow the cake to cool all the way. Cut the cake to form a base for your ice cream mold. (Use a biscuit or cookie cutter for individual servings.) The base should be slightly bigger than the molded ice cream.
- When the cake is cooled and the ice cream well frozen, make the meringue: Use a mixer to beat the egg whites on high until frothy, then add the cream of tarter and beat until soft peaks form. Continue beating and add the sugar one tablespoon at a time until you have stiff glossy peaks. (Lift the beater out of the bowl – if the peaks stay standing up, your meringue is ready.)
- Preheat the oven to 450 degrees F.
- Place the cake on a cookie sheet, then remove the ice cream from the mold and place it on top the cake base.
- Use a spatula to quickly spread the meringue over the cake and ice cream, covering it completely. Make sure the meringue goes all the way down to meet the cookie sheet. (If you think your ice cream is getting soft quickly, you can put the dessert back in the freezer for 15-20 minutes before putting it in the oven.)
- Place on the middle rack in the hot oven and watch closely. Remove when meringue is golden brown, about 3-5 minutes.
- Serve immediately—and enjoy!
In the first experiment, we saw eggs change their form when heated. In this recipe, we see that egg whites also change their form when beaten vigorously! The two changes are caused by the same thing: globular proteins unfolding and forming new bonds with each other. When you beat the eggs, you’re adding air bubbles to the mixture of proteins and water in the egg whites. Some of the amino acids in the proteins are attracted to water and some are repelled by it. The proteins begin to unfold so that the water-loving amino acids can move towards the water, and the others can move toward the air pockets. The unfurled proteins bond with each other, creating a network of protein that traps the air bubbles inside, making a nice fluffy, frothy meringue.
Now, the ultimate question—why didn’t the ice cream melt completely when you put it into that very hot oven? The answer is that the meringue acted as an insulator, slowing down the transfer of heat. It works kind of like styrofoam (but tastier); the air trapped in small pockets in these materials makes them both good insulators.
More Edible Science Projects:
– When egg whites are beaten, they take up 6-8 times more space than liquid egg whites!
– Baked Alaska got its name in the 1870s, but some form of the dessert had been around for much longer. A guest at the White House in 1802 (during Thomas Jefferson’s presidency) described eating a dessert of ice cream inside piping hot pastry.
Watch the egg in the bottle experiment in action with the HST project video.
Learn more about the science of eggs and other foods at the Exploratorium Museum’s cooking science site.
Why do foods brown when they cook? What is flavor? Find the answers to these and other cooking science questions at Science of Cooking.