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Yeast Bread


Sourdough Bread
Dancing Raisins
Whipping Cream and Making Butter
Baking Ice Cream: Baked Alaska
Ice Cream
Dry Ice Ice Cream
Crystal String Candy
Frozen Crystal Pops
Candy Concoctions
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Solar Cooker Banana Boats
Penny for Your Thoughts
Sticky Ice Cube
Make an Edible Model Cell from Candy
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Remember: Be sure to ask an adult before starting any cooking project!
Some projects listed here may require the use of knives, a stovetop, electric appliances, an oven and/or microwave.

Yeast Bread

Have you ever wondered how they get all those little bubbles inside the bread? Did you ever guess there were thousands of tiny workers right inside the dough that are responsible for making all those bubbles?
Wait--it gets even stranger! Those tiny workers (called yeast) eat the sugars in the dough, which breaks them down into carbon dioxide (the gas we exhale when we breathe, as well as the main source of greenhouse gas), and a small amount of ethanol, which is a form of alcohol. This creates the wonderful smell of baking bread.
The yeast spores now have gas. We all know what happens when creatures get gas...

activated bread yeastIf you don't believe me: try this experiment first. In a large measuring cup, add 1 package active dry yeast (be sure it is not past the expiry date) to 1/4 cup of warm water. Add a teaspoon of sugar to the mixture, stir and wait for about ten minutes. What happens? How does it smell?

Quick Yeast Bread
Ingredients:
1/2 package of quick-action dry yeast
1/8 teaspoon of salt
1 tablespoon for sunflower oil (or other vegetable oil)
1 1/2 cups of whole wheat or all-purpose flour
3/4 cup of warm water
Optional: a beaten egg (to glaze the top), poppy seeds, sesame seeds and/or fresh herbs to decorate the top of the loaves

Combine the dry ingredients in a bowl. Add the oil and water, and mix together into a firm dough. Add more flour if the dough is too soft and sticky, or more water if it is too dry.
Knead the dough on a floured surface for 5-6 minutes.
Prepare a baking sheet or loaf pan by greasing it. To do this easily, use a stick of butter like a crayon and colour the surface of the pan.
Place the dough onto the prepared surface and wait until it has doubled in size. Decorate as desired by brushing with beaten egg and seeds and/or herbs.
Bake at 450 o Farenheit for about 20 minutes. It is done when a tap on the top makes a hollow sound. Place the bread on a wire rack to cool.

Now you know how yeast works. How do you think the bubbles happen in cakes and breads that don't use yeast?


Sourdough Bread

Sourdough bread was made years ago by combining lukewarm water and flour, and letting the natural yeast spores in the air find the mixture and do their thing. Most modern people make it using store-bought dry yeast, although the old method also works if you are very patient!
Sourdough starters take a while to grow, and can be propogated for generations once started. In most cases, you will make more starter than you use in a single recipe. The rest can be fed and maintained for future use.
The following recipe link uses all of the starter, which means you won't have any left over to try and store. You can always make extra though if you are interested!
Follow this link for an easy basic sourdough bread recipe.


Dancing Raisins

Needed:
small, very dry raisins
soda water
alka-seltzer tablet
1 tablespoon baking soda
3 tablespoons vinegar
3 clear glasses or jars

Separate your raisins into three piles.
In the first glass, pour soda water until the jar is about 3/4 full. Add the raisins slowly and watch what happens.
Fill teh second glass about 2/3 full with water and drop in the alka seltzer tablet. Slowly add the raisins and watch what happens.
In the last jar, add the baking soda, then fill to about 1/2 way with water. Now aldd the vinegar, and slowly add the raisins.

How do the different glasses compare? What makes the raisins move up? What makes them move down? In what ways are the glasses alike?
The bubbles in this experiment are much like the yeast bubbles above as they are both mainly carbon dioxide. The raisins are heavy and sink in the water, but when the bubbles that are lighter than the water collect on the surface of the raisins, they make the raisin bouyant enough to float to the top. When the bubbles roll off the surface, the raisin loses bouyancy and sinks until more bubbles collect on the surface and it rises once again.


Whipping Cream and Making Butter

These two experiments with the same ingredients yield very different results!

Needed:
whipping cream, divided into two equal amounts
a jar with a tight lid
an adult wielding a cake mixer
a mixing bowl
optional: salt, sugar, vanilla extract

Whipping Cream:
Pour half of the whipping cream into the mixing bowl. Use a cake mixer to mix the cream until it forms fluffy peaks. Add a sprinkle of sugar and/or vanilla extract if desired.
Butter:
Pour the remaining cream into the jar and place the lid on tight. Shake the jar rapidly for 5-12 minutes, until you feel a solid thumping happening as you shake. Remove the lid and pour the liquid into a glass. This liquid is buttermilk. The solid part is butter. What colour is the butter? Add salt if desired.

Why do you end up with different results?
When you whip the cream, air enters into it and fluffs it out. When you shake it, the fat molecules stick together and form a lump. The rest of the liquid separates out into buttermilk.


Baking Ice Cream: Baked Alaska

Baked ice cream that stays frozen? Yes, it can be done!
All you need to do is insulate it first.

Ingredients:
slightly stale angel food cake, homemade or store-bought
ice cream, your favourite flavour, slightly softened
5 egg whites from large eggs, 6 if you use smaller eggs (for food safety reasons, you may wish to use pasturized eggwhites from a carton for this)
1/4 teaspoon salt
1/2 cup of superfine sugar
1 teaspoon vanilla extract

Trim out the cake so that you have an outer shell about 1.5-2 cm thick of cake (about 3/4"). Trim the outside off the top of the cake and the inside off the bottom so that the remaining shape is like a dome. You will use the excess cake to form the bottom and top of the dessert.
On the bottom of a shallow baking dish, lay out strips of cake to cover the bottom of the dessert. Place the hollowed out shell on top, leaving the remaining pieces to be arranged over the top of the ice cream.
Place the eggwhites in a large mixing bowl. Notice how much room they take up.
Beat the egg whites until slightly stiff, adding the salt and cream of tartar, and then adding the sugar a tablespoon at a time, and then the vanilla. How much room do they take up in the bowl now? Why do you think that is? What takes up the extra space? (hint: it's not the sugar!)

For the next steps, you will need to act quickly. Add the softened ice cream to the centre of the cake, then arrange the remaining cake pieces over the top. Spread the meringue (this is the fluffy egg white mixture) over the entire outside of the cake. Have an adult bake on the middle rack (or one lower if your oven is short or your dessert turns out tall) under a broiler at 500 o Farenheit for about 3 minutes, watching it closely. The meringue should be golden brown. Serve immediately.

                                   baked Alaska construction                        baked Alaska                        baked Alaska, ready to eat
Now that you've seen it done, why do you think this works? Why doesn't the ice cream melt all over the place? Compare the weights of angel food cake, meringue, styrofoam insulation, and copper tubing. What do you think makes the styrofoam, angel food cake and meringue good insulators? Besides being light, what else do they have in common? What other insulators and conductors can you think of?

Still interested in insulation and heat transfer? Try these challenges:

  1. Using a timer and an ice cube, challenge groups of students to melt it as fast as possible using no appliances or other mechanical means.
  2. Repeat the same exercise but this time try and keep the ice cube frozen as long as possible.

How successful were you? What methods worked best in each situation? How can you use this information to improve winter clothing and food storage? What other applications can you find for this activity?


Ice Cream

To make ice cream this way, you need to take advantage of the fact that salt water has a lower freezing point than regular water. When the salt is added to the ice in the outer bag, it melts quicker and flows around the inner bag. This provides more surface area in which to freeze the ice cream.

Ingredients:
1 cup cream or evaporated milk
1 cup milk
1 cup sugar
2 teaspoons vanilla extract
two dozen or so ice cubes
1/2 cup coarse salt (table salt will also work)
one large-sized freezer bag with a zipper closure
one medium-sized freezer bag with a zipper closure
duct tape long enough to seal the tops of both bags plus about 4"
optional: oven mitts or winter mitts

Combine milk, cream, sugar and vanilla in a bowl. Pour into medium freezer bag and zip closed. Reinforce the seal with some of the duct tape. Pour the ice cubes and salt into the larger bag. Put the medium bag inside the larger one. Zip it closed, and reinforce it with duct tape. Now find a friend and play catch (or toss and catch it yourself) so that it is continuously shaken for 10-12 minutes. You may wish to wear mitts to protect your hands from the cold. Once the time is up, cut open larger bag and pull out medium bag. Turn upside down and cut a large hole in one corner. Squeeze out your ice cream and enjoy.


Dry Ice Ice Cream

You can also make ice cream using dry ice (frozen carbon dioxide). We use the recipe mixture above, then add dry ice to it.
Details for this can be found on the advanced experiments page.


Crystal String Candy


Needed:
clean cotton string with a rough texture
1 cup sugar
water
plastic wrap

In a saucepan, mix the sugar with 1/3 cup of water and stir until dissolved. To speed up the experiment, have an adult heat the mixture until it begins to boil, then remove from the heat.
Wet your string with water, then squeeze it dry by pinching it and running it through your fingers a few times. Dip it into some sugar, then immediately arrange it so that the centre half is in the dissolved sugar with the two ends draped outside the saucepan. Cover the whole thing with plastic wrap, and let it sit overnight. Check the string for crystals. Have any formed yet? If not, reposition the string and check the next day. When the string is ready, place it on some paper towels to soak up any liquid, then you can eat the crystals off the string if you wish.


Frozen Crystal Pops

A simple, yummy way to investigate ice crystals.

Ingredients:
your favourite fruit juice
ice cube tray, popsicle sticks and plastic wrap or foil or popsicle tray

Fill your tray with juice. Cover with plastic or foil, insert sticks and freeze.
When served, place one on a plate to be observed while you eat the others. What is that white coating that forms on top? How long does it take to melt? What happens when you suck on the frozen juice?


Candy Concoctions

Experiment with crystalization by making candy.
This is an adult-driven, stove-top experiment. A responsible adult needs to handle the very hot candy; others involved may record the temperature, prepare the work surface and make observations. Be sure that all pouring is done close to the target surface and away from all people.
This can be done in a single, multi-staged experiment, or by trying one kind of candy at a time.


You will need:
a reliable candy thermometer
3 cups sugar (white or brown)
1 cup water
several oven-safe containers, pre-warmed and greased with butter or a marble slab

optional: vanilla, peppermint or other extract (amount will vary depending on what flavour you use, and when and how you add it, but for the total should be about 1/2-1 teaspoon)
            *add any flavourings only after the candy has been removed from the heat

Heat the mixture over medium-high heat until it begins to boil, then turn heat down to medium-low for better control.
For the multi-staged version. you will be removing candy syrup from the pot at various points in the cooking process. Have several oven-proof containers ready to place these in ahead of time. It is best to keep these warm to avoid cracking from temperature shock. You can also pour these directly on a marble board instead if you have one.
Prepare the oven-proof containers or marble board with a thin layer of vegetable oil or powdered sugar to help avoid sticking.

Tips:
Stir the mixture only until all the ingredients are dissolved; cover the pot for about 2 minutes to allow crystals to wash down the sides, but never stir in the crystals from the side of the pot as it will change the crystal structure of the rest of the mixture. After it is all dissolved, do not stir!

Try making candy glass by pouring out syrup at the hard-crack stage onto a prepared marble slab and let harden. Sugar glass has been used in place of real glass for special effects in movies.

Candy stages: (temperatures in Farenheit)
Thread           230o        The syrup makes a coarse thread when dropped from a spoon                                        Used for making glazes
Soft Ball         234 o      Syrup makes a small ball that doesn't disintegrate in cold water unless touched      Used for fudge and fondant
Firm Ball         244 o      Syrup makes a ball in cold water and holds its shape even when touched            Used for caramels
Hard Ball         250 o      The ball is more rigid but pliable                                                                                Used for taffy
Soft Crack      270 o      Forms threads when dropped in cold water that will bend                              Used for butterscotch and toffee
Hard Crack      300 o      The syrup forms threads that are brittle                                                        Used for hard candy and peanut brittle
Caramelized sugar    310-325 o                Turns golden brown                                                                              Used for glazes and coatings
At 350 o, it will turn black.


Popcorn

With the advent of microwave popcorn, many kids have never had the experience of watching a kernel of corn pop. If you have a wire popper, omit the oil and use half the kernels. If you have a transparent pot, you will be able to watch the kernels pop the whole time.
What makes them pop? Even though the kernels are dry, there is still some moisture inside. As the kernels heat, the steam expands and the kernel explodes into popcorn.

Ingredients:
2 tablespoons vegetable oil
1/2 cup dry popcorn kernels
salt
optional: melted butter or grated cheese

Heat a heavy cooking pot for about 1 minute on high, then add the oil. Add 3-4 kernels and watch for them to pop. Once those have popped, add the remaining popcorn kernels. Hold the lid on the top and keep the pot moving back and forth so that the popcorn doesn't scorch. Keep popping until the popping rate decreases, then remove from heat. Add salt and any butter or cheese desired.


Solar-Cooker Banana Boats
Build a very effective and economical solar cooker from cardboard and aluminum foil, then enjoy some fun warm treats.
Follow this link for building plans.

Ingredients:
a large unpeeled banana, cut in half width-wise, and slit down the middle
aluminum foil
your choice of any or all of the following:
chocolate chips
mini marshmallows
skor bits
caramels
butterscotch or peanut butter chips
chopped nuts

Stuff your fillings into your banana, then wrap it in aluminum foil. Place in your black container, then into the cooker. When used in full sun in southern Ontario in late July, ours took about 50 minutes to fully cook. Be sure to handle your container with oven mitts when removing from the cooker--it will be very hot!


Penny for Your Thoughts
This experiment isn't strictly edible, but since it uses items found in the kitchen, I've chosen to include it here.

You will need:
a penny
2 tablespoons of water, plus a separate small glass or bowl of water
a couple of drops of dish soap or pine sap
a small dry leaf, or conifer needle: use one from outdoors or you can use a bay leaf or other dried herb or tea leaf
an eye dropper

First, using an eye dropper, count out how many drops of water you can fit onto the top of a penny before the water runs off. Record or remember that number. Now add a drop of soap or pine sap to the water, dry the penny off and try the experiment again. Did the soap or sap allow for more or less water to stay on the penny?
Now, float a leaf or needle on the water in the bowl. Watch how it moves. Now take it off the surface and add a little soap or sap along half of one edge, then set it carefully back down on the surface. What happens? Why?
These experiments explore the concept of surface tension. The soap or sap acts to break the surface tension creating a much different effect than when none is added. Try using other things than sap or soap. What happens when you add vinegar? How about milk or juice?


Sticky Ice Cube

You will need:
an ice cube
a length of string or yarn about 10 cm or 4" or slightly longer
table salt

The challenge: lift the ice cube with the string at least 6" (15 cm) without dropping it.

Of course, if you looked at the materials listed, you may have figured out how to do it! The trick is to sprinkle a little table salt on the top of the ice cube, then place the string on top. Wait a few seconds then pull the string and the ice cube will come along with it.

What is really happening here?
Just like road salt melts snow and ice outdoors, the salt melts the top of the ice cube. When you place the string on top, the string sits in this tiny puddle of water. Since there is only a little salt, and the ice cube is much larger, the surrounding ice causes the water to refreeze after a few seconds, and the water freezes around the string. This freezes the string to the top of the ice cube and allows you to pick it up using only the string.
Did you know: while most substances take up less volume when they move from liquid to solid states, ice actually takes up more volume than water. You can see this if you freeze a plastic or glass bottle of water. If filled to the top, the plastic will stretch and expand, and possibly burst; the glass container will break. This is the reason that ice floats on top of water instead of sinking.

For more fun recipes that you can eat, click here.