Oobleck...Newton's in the Kitchen

Cornstarch has the ability to thicken liquids in the kitchen when it is heated. However, if you just mix cornstarch with water, you'll notice a few unique properties. Using the following recipe, try making this and answer some of the questions below for fun.

Oobleck Recipe
1 cup water
1 ½ – 2 cups corn starch
1-2 drops of food coloring of your choice

Place the water in a bowl or cup. Add the food coloring to the water. Then slowly add the corn starch stirring after each addition, until the Oobleck is the right consistency. It should be able to flow through your fingers, but still feel solid when you press down on it with your hand. Enjoy! You can keep the Oobleck in a Ziplock bag in the refrigerator for a few days. Dispose of the Oobleck in the trash can...not the sink!

A. Take some Oobleck in your hands and spread your fingers out wide. What happens?

B. What happens when you push really hard on it. Place it in a container and punch it down with your fist. How does it feel?

C. Roll the Oobleck in your hands like a meatball. Then place it in someone else's hand (your your other hand if you are working alone). What are your observations? D. Do you think Oobleck is a solid, liquid, or gas? Why?


Teacher's Corner:

Uncooked corn starch particles are structured in both crystalline and noncrystalline arrangements. When you gently mix the water into the cornstarch, the noncrystalline structures begin to absorb most of the water. If you smack or stir it rapidly, you increase the temperature and pressure which causes more noncrystalline structures to form. These new noncrystalline structures absorb more of the water and the mixture becomes even thicker, and it looks more like a solid. When you stop stirring or placing pressure on the Oobleck, the number of noncrystalline structures decrease and water is released, creating the "soupy" mixture. This type of substance is called a "non-Newtonian fluid." It does not behave in the same way as Newton's Third Law of motion states. Even though it has different properties from Oobleck, Ketchup is another example of a non-Newtonian fluid.

Fail-proof gravy

There are many recipes out there for the "perfect gravy," but I have found that the ones I tried do not work all of the time. Too many times I have lumps or worse yet, it never actually thickens!

Here is a recipe that uses cornstarch (which is thought to have double the thickening power of traditional flour) as the thickener than the traditional Beurre Manié (flour and butter mixture). I hope you will use this for your Thanksgiving turkey, or just your Tuesday night chicken...enjoy!

Fail-Proof Thanksgiving Gravy

2TBSP drippings from meat (with the good brown bits or "fond")
2 cups chicken stock (or homemade turkey stock)
2 TBSP cornstarch
4TBSP water
Thyme (dried or fresh)
Salt and pepper to taste
1 TBSP of heavy cream

Skim off the excess fat from the roasting pan (or saute pan) leaving only about 2 TBSP. Add the 2 cups of stock to the pan over med-high heat to de-glaze. As it is heating, use a wooden spoon to scrape the bottom of pan getting all of the good bits or fond. This is what will really add all the flavor to your gravy. In a separate bowl, stir together the cornstarch and water to make a slurry. Whisk this into the roasting pan and allow it all to come to a boil for at least one minute. Add the thyme and salt and pepper to taste. Stir in the cream if using to give a smoother and silker final product. Serve immediately. Do not let this cook for too long (more than 10-15 minutes), or the cornstarch will begin to break down and lose some of its thickening properties.

What makes cornstarch thicken liquids?

What do gravy, coffee cake, and icing on your birthday cake have in common? Well, they most likely were made using cornstarch.

As the name says, cornstarch is the starch of corn. It is usually extracted from the endosperm of the kernel of corn. If you have ever ran cornstarch through your fingers you know that it has very unique feel, almost like talcum powder. This texture actually acts as an anti-caking agent in confectioners sugar and cake flour. Actually, if you are ever in need of cake flour for a recipe but are clear out of it in the pantry, add 2TBSP cornstarch for every 1 cup all-purpose flour and voila...cake flour. (You will want to sift these ingredients together to make sure they are equally distributed).

Cornstarch is most widely known for its thickening properties when added to hot liquids. As the cornstarch is heated (must be boiling to get the maximum amount of thickness), the molecules begin to break apart and they run into the other starch molecules. These starch molecules interlock to form a fort of net that creates a barrier for the water molecules. It slows down the water molecules from moving in the liquid. This promotes the thickening of liquids like gravy, soups, and sauces. Below is an image that I found at cdavies.wordpress.com/2006/10/05/starch/. I think this is a good visual. You can see the the water is basically being trapped between the starch molecules.

Homemade Caramel Popcorn

Cracker Jack is one of those wonderful foods that is great at a baseball game, but I always enjoyed the homemade popcorn even better. At my wedding shower (13 years ago now), everyone gave me a recipe to try out in my “new kitchen.” My Aunt Janet (who is a fabulous cook and baker by the way), gave me the recipe to her homemade caramel corn. I have made it before, and it has been great each time. I have seen on other sights that it can be difficult to make and that it can turn out grainy or just too hard and brittle. So, I thought I would delve into the recipe and look at some of the ingredients and determine why this recipe is such a good one. Would it work without the baking soda...what does that do for caramel anyway? What would happen if I didn't put it into the oven afterwards? Enjoy this great popcorn...it's a winner!

Aunt Janet's Oven Caramel Corn

3 ½ quarts (about 14 cups) of popped corn

3/4 cup brown sugar

½ cup butter

½ tsp salt

1/2 cup light corn syrup

½ tsp baking soda

Place the popped corn in a large roasting pan. Heat butter, sugar, salt, and corn syrup in a large pot. Stir occasionally until bubbles form around the edges.

Cook 5 minutes. Remove from the heat and stir in the baking soda till foamy. You must stir at this stage so the caramel doesn't overflow the pot...it will expand.

Pour over the corn and stir to coat. Work quickly once you pour it onto the corn to coat evenly.

Bake 1 hour at 225^o F, stirring every 15 minutes (don't skip this step, it makes a difference in the final texture). Store in an air tight container.

Why does this recipe work?
If you have ever had a candy apple and almost lost your tooth, you know will understand why it is important to add the baking soda to the caramel corn. The baking soda reacts with the acidity of the brown sugar and corn syrup and produces CO2. This aerates the caramel and makes the end product more palatable and honestly just easier to eat. The only problem with adding the baking soda that I could see was a dullness in the color of the popcorn. It lost some of it's luster after it was baked. I tried a batch without the baking soda, and although it was shiny, I could hardly eat it without fears of going to the dentist! Without the baking soda it was like you melted a Werther's Original hard candy on top of some popcorn...not easy to eat.

I also wondered why you had to bake it after it had already "cooked." From my tests, it seems that the baking melts the sugar slightly over the popcorn and adheres it to the corn. When we didn't bake it, it was almost impossible to eat. Again, extremely hard and brittle.

I hope this recipe will serve everyone well, and become a favorite in your family as well.

Can you make your own microwave popcorn?

I was at the store and saw that a 9oz box of microwave popcorn was $2.87, but the 32oz of popcorn kernels was only $1.87. In these times of economic awareness, it is good to pinch pennies wherever you can. However, the idea of taking out a pot, and cooking the popcorn over the stove makes the microwave variety worth the price. Or does it? If I could take the kernels and pop them in the microwave...that would be a savings of time and money. But does it work? I set off to the kitchen to see.

I took ¼ cup of popcorn kernels and put them into a brown lunch bag. I folded the top of the bag over 2 times, and pressed the “popcorn” button on my microwave. WOW! Within 2.5 minutes, I had 6 cups of popped corn. There were a few kernels still left in the bag, but that is to be expected. I was surprised at how well it worked!

Now, the microwave popcorn companies have something over on my newly popped corn...flavor. No worries. I have two great recipes below to spice up the popcorn to make it the tasty treat we all know and love. If you have any other savory popcorn recipes...please pass them along.

I will admit that this last step of adding flavor is more time consuming, but not by a lot. However, because the ingredients you are using are coming from your cabinets, you can change them to suit your tastes and dietary needs. Plus, there are no worries of perfluorooctanoic (PFOA), which is a carcinogen that is found in the coating of some microwave popcorn bags.

This experiment was clearly a success!

Cheesy Parmesan Popcorn (EASY RECIPE)

¼ cup popcorn kernels

1 brown paper lunch bag

5 TBSP butter (melted)

½ tsp rosemary or thyme

¼ - ½ cup freshly grated Parmesan cheese

Salt to taste

Put the kernels in the bottom of the paper bag and fold the top of the bag over a few times, but be sure to leave enough room for the popcorn to expand. Put the bag in the microwave and push the “popcorn” button or cook for about 2 minutes (depending on your microwave).

While the popcorn is cooking, melt the butter and add the rosemary or thyme. After the popcorn is finished cooking, put it in a large bowl and pour the butter over it to coat. Sprinkle the cheese on top and toss until well coated. Serve warm. Enjoy!

Oscar Winning Movie Theater Buttered Popcorn (EASY RECIPE)

¼ cup popcorn kernels

1 brown paper lunch bag

8 – 12 TBSP butter

Put the kernels in the bottom of the paper bag and fold the top of the bag over a few times, but be sure to leave enough room for the popcorn to expand. Put the bag in the microwave and push the “popcorn” button or cook for about 2 minutes (depending on your microwave).

You will be making clarified butter, which acts much like the butter-oil movie theaters use. Put the butter into a microwave safe glass measuring cup. Microwave until the butter has completely melted. Let it stand on the counter for a few minutes so that it can separate into three layers. Skim off the top foamy layer. Then slowly and carefully pour the clarified butter (the middle layer) into a glass container, and discard the milk solids on the bottom. Pour 3 TBSP of the hot clarified butter over the popcorn and toss in a large bowl. Pick out your favorite movie and enjoy!

Why does popcorn POP?

The simple answer is water, but that doesn't begin to cover it...I hope this will.

Popcorn is a grain like wheat, rice, or even “regular” corn. Grains have three main parts: the pericarp (the outer covering), the endosperm (the inside consisting of mainly starch, and small amounts of fat, protein, and water), and the germ (allows it to grow when planted).

So why don't we go the movies and have a big bag of popped wheat or rice? Well, the main reason is the pericarp (sometimes called the hull). The pericarp of wheat and rice is very porous, which allows steam to escape while cooking. However, popcorn has a hull that is very strong and non-porous. This hull is even different from the corn that's on the cob you like to eat too...popcorn is unique.

As you cook the popcorn, the water inside the endosperm heats up, becomes steam, and expands. Because of the “hard” shell of the pericarp, the steam cannot escape and the pressure raises inside the kernel. When internal temperature of the kernel reaches a high enough temperature, the pressure inside it becomes too great and POP! The hull turns inside out with the explosion, and the starchy endosperm is exposed. This is the soft white carbohydrate we most closely associate with popcorn. The darker part of a popped kernel is the leftover pericarp.

Have you ever popped a bag of popcorn and had a lot of kernels leftover in the bottom? Why? Well, there are a few factors that could cause this. Conditions have to be just right for those kernels to turn into tasty treats. Try these three mini-experiments (with the help of a parent or teacher if necessary), to see why.

Experiment A: Try popping popcorn at a low temperature (below 300F). Does the popcorn POP?

***** The temperature within the kernel must reach 400F. The pressure will not be great enough for it to POP without the right amount of heat. *****

Experiment B: Leave a few kernels of popcorn out in the sun for a few days or in a warm oven for a few hours. Then try and popping the corn. Does it work?

***** The kernel must have an exact moisture content of between 13-14%. Popcorn growers actually harvest the popcorn when the moisture content is about 16% and then the kernels are carefully dried until the exact percentage is just right for popping. *****

Experiment C: VERY CAREFULLY take a pin or knife and poke or cut small holes into some kernels of popcorn. Will it POP?

***** The pericarp cannot be damaged in any way. If there is even a small pinhole in the kernel, the steam will be able to escape, and the pressure will not be great enough for the kernel to explode. *****

Some Food for Thought...

Did you ever wonder what makes popcorn pop, bread rise, or jello jiggle? It may be the chemistry teacher in me (I taught high school chemistry for many years before staying home with my kids), but I often have these types of questions as I cook. Why do we need to add certain ingredients to make the recipe “work?” Could I use something else instead? What is the chemistry behind a recipe? I want to explore these answers and hopefully stumble onto some new questions so that I may be a better cook, and scientist for it. My goal is to explore and gain understanding of the link between cooking and chemistry, and pass on some of this knowledge to those who are willing to read about it.

My hope is that this site will be used by teachers, parents, home cooks, and kids alike. It could serve as a supplement to a lesson plan or homeschool curriculum, as a way to help find the perfect ingredient to add to your “favorite” recipe, or even just an activity a parent and child could do on a rainy day. Each week there will be a theme or food that I investigate. I will try to map out some of the history behind it, find out unusual facts, and hopefully answer some common questions as well. At least one day a week I will have a recipe that will be a delicious way to “test” the facts. I look forward to hearing from you for topics suggestions for later posts or ideas that you have for recipes using these ingredients. Let's get cooking!