Chewy, Gooey Caramels

Here's another recipe for one of Dr. B's favorite candies - caramels!

What you need:
1 cup heavy cream
12 tablespoons butter (1 1/2 sticks), cut into small pieces
2 2/3 cups light brown sugar
1/2 teaspoon vanilla
Water
Large saucepan with cover
Stove
Candy thermometer
9" x 9" baking pan
Nonstick cooking spray
Spoon
Spatula
Knife
Waxed paper or plastic wrap

Coat the baking pan with nonstick cooking spray. Put the cream, butter, brown sugar, vanilla, and water into the saucepan. Heat on low for a few minutes while stirring until the butter melts and the sugar dissolves. Turn the heat up until the mixture boils, then cover and let cook for three minutes. Uncover the pan, turn the heat down, and continue to boil; don't stir the mixture during this time. When the candy thermometer reads 250^oF, remove the pan from the heat and pour the caramel into the pan. This mixture will heat up quickly - make sure it doesn't burn! Let the caramels cools until they are solid but still slightly warm. To get them out, turn the pan upside down onto a piece of waxed paper or plastic wrap and push on the bottom of the pan. Cut into small pieces and wrap individually. Enjoy them!

So, what's so scientific about making caramels? While the mixture of cream, butter, and brown sugar is yummy enough on its own, it tastes even better after it cooks a while. This is an example of the Maillard reaction, which takes place between a protein (in the cream) and a sugar. This is the first type of candy you've made that contains any proteins. When the two molecules react, the mixture turns brown. It's the same reaction that occurs when you make toast (the flour used to make bread has both protein and sugar) and when onions are cooked until they turn brown. Of course, caramels, toast, and onions (while all delicious) don't taste at all alike. Each of these foods contains lots of other molecules that give them their particular flavor. But the fact that they all turn brown is due to the same reaction!

Spot the Differences

This month, we've talked about three different types of sugar molecules - sucrose, glucose, and fructose. But what do they look like? The pictures below show these three molecules, and some other types of sugars, some of which may sound familiar:
Notice that all of the sugars are made from only three elements: carbon (C), hydrogen (H), and oxygen (O). It should also be pointed out that there is actually a carbon atom at each of the corners of the hexagons and pentagon, but the picture gets too crowded if we show them all.

Even though these sugars are very similar, there are little differences. Look carefully at these pictures, and see how many of those differences you can spot!

Want Some Khandakah?

It may seem like people must have always had sugar to eat, but that's not true. The story of sugar (actually, sucrose) production spans 2500 years and involves much of world history (and some science, too!). Humans used honey as a sweetener for thousands of years, but in about 500 BCE, people in India figured out how to change the juice of the sugar cane plant into solid sucrose crystals. Within a few hundred years (things moved slower back then), this knowledge had moved into Persia (now Iran) and Arabia. In fact, an Arabic/Sanskrit word for "sugar" is "khandakah", from which we probably get our word "candy"!

From about 1000 - 1200 CE, Europeans invaded the Middle East (primarily the land that is now Israel and Syria) for a variety of religious and political reasons that won't be discussed here. One of the things that the Crusaders brought back to Europe was sugar. Sugar was mostly used as a medicine (although it wouldn't really cure anything) until someone created the first candy, sugar-coated almonds, in around 1200 CE. By the 1300's, sugar had become fairly common, but was very, very expensive. At this time, it was grown in Italy, Greece, India, and Arabia. In the 1600's and 1700's, colonies were established in the "New World", and many of them also grew sugar cane. In fact, the need for labor on sugar plantations was one of the main reasons why African slaves were brought to the Americas.

Today, table sugar (sucrose) comes from the juice of either sugar cane or sugar beets. These juices naturally contain a lot of different chemicals, such as water, proteins, starches, coloring agents, and fibers. In fact, only 10-15% of the juice is actually sucrose. The plants are harvested and mashed, and the juice is collected. It is then heated to evaporate the water. The type of evaporator that is still used today was developed by the African-American inventor Norbert Rillieux of New Orleans; this device was faster and safer than the older methods. Once the sugar crystals form, they are cleaned and dried. White cane sugar, the kind most commonly used in the U.S., is 99% pure sucrose.

Crystal Clear

The last couple of activities have talked about crystals, but what are they? Is a crystal just another name for a solid? And are all crystals the same?

Crystals are always solid, but not all solids are crystals. Glass and many plastics are examples of solids that are not crystalline. In a crystal, the atoms or molecules are piled together in a very neat, organized way, and they're often arranged in familiar shapes like these:The names may seem funny to you, but you probably recognize squares, rectangles, and hexagons. Each of the colored balls represents an atom or molecule. For example, table salt (sodium chloride) has a cubic crystal structure. Half of the balls are sodium atoms, and half are chlorines. These shapes are just building blocks. A real crystal would have zillions of these blocks, all exactly the same, all piled up one on top of another. Table sugar, or sucrose, is made up of monoclinic blocks, with the green balls representing individual sugar molecules.

When you made jack wax and nut brittle, you learned two ways to keep large crystals from forming - by cooling quickly, or by adding some other substance. Let's talk about why these methods prevent crystallization. Imagine that you're a young child again, trying to make a tower out of building blocks. It's easy to get the first few blocks in place, but then it gets harder. If you had to construct the tower very quickly, it would probably fall down sooner than if you could build it slowly because you would be able to place each block just where you wanted it. In the same way, cooling a liquid very quickly doesn't let big crystals grow. Now imagine trying to build a tower with some cubical blocks and some that had a triangular shape! This wouldn't work very well either, because it's harder to fit the triangles into your pile. So, adding a molecule of another shape (like glucose and fructose in corn syrup) also makes it hard for crystals to get big.

So, was this explanation crystal clear???

A Little Brittle

In the last experiment/recipe, you learned how to stop crystals from forming by cooling very fast. In this activity, you'll learn another way to prevent crystals. In the kitchen, "table sugar" usually means a molecule called sucrose, which is usually made from sugar cane or sugar beets. Corn syrup, on the other hand, contains other sugar molecules, called glucose and fructose. If you add these types of sugar to the sucrose, the glucose and fructose lead to "mistakes" when crystals try to form, and the result is - no crystals (or at least, not very many)!

This is a recipe for nut brittle, which uses corn syrup mixed with table sugar to keep crystals from forming. The presence of crystals would not change the taste of the candy, but would make it feel gritty in your mouth. Nut brittle is most commonly made with peanuts, but you can also make it with other nuts, if you don't like peanuts or can't eat them.

What you'll need:
1/2 cup light corn syrup
1 cup sugar
1 cup dry-roasted peanuts or other nuts
2 teaspoon butter
1 teaspoon vanilla extract
1 teaspoon baking soda
Salt (if you want)
Microwave oven
Large microwave-safe bowl
Spoon
Baking pan (10" x 10")
Oven mitts

Rub the baking pan with about 1 teaspoon worth of butter and put it aside. Mix the corn syrup and sugar in the bowl and microwave on high for 4 minutes. The sugar should have started to melt, but still be clear. Remove from the oven and stir in the nuts. Be careful - the bowl will be VERY hot. Microwave on high about 3 more minutes or until the mixture turns light brown. Take the bowl out of the microwave again and stir in the other teaspoon of butter and the vanilla extract. Microwave on high again for 1 minute. Remove the bowl again, and stir in the baking soda (what do you see happening?). Quickly pour the mixture into the baking pan and let it cool. When the brittle is safe to handle, slide it out of the pan, and break it into small pieces. If you're going to store it, make sure it's in an airtight container.

This recipe includes another chemical reaction that has nothing to do with sugars or crystals. When you added the baking soda, the brittle got cloudy because thousands of tiny gas bubbles formed. Where did they come from?? When baking soda is heated to 160^oF, it gives off carbon dioxide gas. The sugar/nut mixture is much hotter than this, so the gas is given off very quickly. The bubbles don't change the taste of the nut brittle, but do make the candy lighter and easier to chew.

Marvelous Maple Candy!

Do you like maple syrup on your pancakes or waffles? Then try this candy, which is sometimes called "Jack Wax" (although that name doesn't make it sound very tasty!). You'll heat the syrup, then pour it directly onto snow or ice, forming a taffy that can be formed into fun shapes. This recipe works best if you have fresh snow available, but crushed ice is OK, too. A couple of warnings - be very careful with the hot syrup, as it can burn you. Also, if you have braces or other tooth problems, maybe you shouldn't try this very sticky candy (check with an adult first).

What you'll need:
1 cup maple syrup (genuine syrup, not the artificial kind)
Large saucepan
Spoon
Fork
Small juice glass
Large bowl
Stove
Candy thermometer (optional)
Water
Enough snow or crushed ice to fill the bowl

Put the snow or ice into the large bowl. Fill the small glass about 3/4 full with water. Pour the maple syrup into the saucepan and heat to boiling. Once the syrup starts to foam, reduce the heat to low. Keep stirring. In the beginning, the syrup will create a LOT of foam as the water boils off. Be sure that it doesn't boil over onto the stove - remove it from the heat for a few minutes if necessary.

While the syrup is heating, you should test it by letting a drop fall from the spoon into the water in the juice glass. You'll notice that, at first, the drop loses its shape right away, but as the syrup gets hotter, it forms little balls that fall to the bottom. And these balls get tighter as the temperature goes up. Candymakers call these the thread stage, the soft-ball stage, and the hard-ball stage.

You'll need to keep heating for at least 10-15 minutes. If you're using a candy thermometer, you can stop when the syrup reaches 240^oF; this is in the soft-ball stage. If you don't have a thermometer, uses the water test described above. Then pour a little of the syrup over the snow or ice in a ribbon. It will harden and cool really fast. Use a fork to pick it up. If it is soft but stretchy, then the syrup is at the right temperature, and you should pour most of it over the snow. If the syrup stays mushy even when cooled, heat it a little longer. You can eat this candy mixed with the snow or ice, or save it for later. If you're saving it, put it in the refrigerator.

Pouring the syrup onto ice cools it quickly, and the solid candy is smooth and shiny, not bumpy like the rock candy was. The crystals in rock candy take time to grow. When the liquid is poured onto snow or ice, there is no time for the crystals to even get started, so the solid is smooth.

Candy Rocks!

Here's a way to make rock candy (don't worry - it doesn't actually contain rocks). Rock candy is made up of large sugar crystals grown on a string. This experiment will take a few days, but the results will be delicious!

What You'll Need:

Glass jar

Pencil or other thin piece of wood (long enough to fit across the mouth of the jar)

Cotton string with a rough surface

3 cups sugar

1 cup water

Pan

Stove

Spoon (plastic or wood is best)

Paper towel

Food coloring (if you want)

Cut a piece of string about 8 inches long. Tie one end around the pencil. Place the pencil across the mouth of the jar, with the string hanging down inside. The string should reach almost to the bottom of the jar, but shouldn't touch the bottom or sides. If it's too long, cut the string or wrap it around the pencil to shorten it. Put the pencil and string aside.

Put the water in the pan and boil it. When it is boiling, start to add sugar, about one teaspoonful at a time. Stir until the sugar dissolves completely, then put another teaspoon in and stir that until it dissolves. Keep adding sugar until it won't dissolve any more (you may use less than 3 cups). You need to get as much sugar as possible into the solution in order to get big crystals quickly. There shouldn't be any undissolved sugar on the bottom of the pan. If you want colored rock candy, add a few drops of food coloring at this time.

Carefully pour the sugar solution into the jar (remember that it's very hot!). Make sure that there are no sugar granules in this solution. Put the pencil over the mouth of the jar as before, and let the string hang down into the solution. Place the jar somewhere that it won't be disturbed. Cover it with a paper towel to keep dust out.

Now you wait! The shiny sugar crystals will grow slowly, and you should see them starting in a day or two. It will look something like the picture on the right. In about a week, you'll notice that the crystals aren't getting any bigger. That's when you can take them out of the jar to dry. Before you enjoy eating your rock candy, take a close look at it. What shapes do the sugar crystals have? Is this the same shape that the original sugar granules had?

Go Nuts!

Here's a quick way to make delicious sugar-coated nuts, while learning something about sugar's phases. A phase is a physical state of matter - you probably know the terms solid, liquid, and gas. We're used to thinking of sugar as a solid. When you dissolve it in a liquid, like coffee, tea, or milk, the sugar molecules break up and float around in the liquid. But that's not really the same as liquid sugar, which would be a liquid that is made up of pure sugar. We can usually make a liquid from a solid by heating the solid up, thereby melting it. You're familiar with the way that ice melts - well, you can do the same thing with sugar. It just needs to be heated to a very high temperature, 365^oF.

What you'll need:
1/2 cup table sugar (sucrose)
1 cup nuts (peanuts, walnuts, almonds, or whatever you like)
Metal saucepan
Spoon
Stove
Magnifying glass

Look at the sugar crystals with a magnifying glass. What do they look like? Put the sugar into the saucepan and heat on low-to-medium until the sugar melts. Keep stirring to help the sugar melt evenly. Scrape the sides of the pan, and try to prevent the sugar from turning brown. When the sugar is all melted and has started to boil, remove the pan from the heat. Add the nuts quickly and stir to coat. Let the sugar-coated nuts cool for at least 30 minutes. Be very careful when doing this experiment because you can get burned by the hot sugar. Have an adult help you. Before you eat the nuts, look at the sugar coating with a magnifying glass again. Does the sugar look the same?

Before melting, the sugar looks like tiny, perfect cubes. These are sugar crystals. But after it have been melted and cooled, the sugar doesn't look so perfect. When a liquid is cooled pretty quickly, the molecules don't have time to organize themselves into perfect crystals, and so they look irregular. In the next experiment, you'll make rock candy, which has beautiful sugar crystals. But they will take a long time to form!

Sweet Science

You may think of candy as simply something yummy to eat, but there is actually a lot of science behind these sweet treats.

Candies are sweet because they contain one or more kinds of sugar. To a chemist, the sugar you most commonly use is called sucrose, but there are many other sugars - glucose, fructose, ribose, maltose, and lactose, to name a few. You'll learn about some of these other types of sugar later this month.

While some candies are almost all sugar, most contain other ingredients, such as milk, flavorings, butter, or cocoa. You'll get recipes for several different candies, and will learn what makes them look and taste the way they do. And while it's usually a bad idea to eat experimental results, that rule doesn't apply to the experiments this month! You can enjoy all of them when you're done!