The Science of Food: Emulsions on your Salad!

Emulsion Repulsion: Science on your Salad!

A simple way to explain an emulsion is as a suspension of two liquids within each other that normally would not mix (like oil and water).  Picture a cup with vinegar.  If you pour oil into the vinegar, the oil will float on top of the vinegar because it is less dense.  What happens if you briskly whisk them together?  Well, the liquids start to mix together and tiny droplets of each liquid become suspended within each other.  When they are uniformly dispersed in each other (evenly mixed) then you have an emulsion.

A simple mixture of oil and vinegar will ultimately separate back into vinegar and oil because at a molecular level, there is nothing holding the two kinds of liquids together. This temporary emulsion just happens because of the whisking. To get a permanent emulsion of these two liquids you need a third ingredient to hold the two immiscible (non-mixing) agents together and prevent them from separating.  This ingredient is called an emulsifying agent.  This agent is like a mutual friend who likes both the oil and the vinegar and holds them together.  It creates a weak chemical bond with each liquid and becomes like a bridge between them.  Eggs are a very common emulsifying agent as is mayonnaise and hollandaise sauce.

Now that you understand emulsions, go into your kitchen and make your own!

egg-whisk-2
 Creative Commons License photo credit: LDCross

Materials:
Measuring cup
Measuring spoons
Vegetable oil
Vinegar
2 Mixing bowls
Whisk or hand egg beater
1 Egg

Procedure:

Part 1
1. First grab an adult to help you.  Also, we will be using a raw egg, so this experiment is not for eating, it’s just for experimenting!
2. In a mixing bowl, place ½ cup of vegetable oil.
3. Add one teaspoon of vinegar and use a spoon to gently mix them together.  Observe what happens.
4. Now, use the whisk or a hand eggbeater to mix the vinegar and oil.  What happens now? 
5. Watch the mixture for a few more minutes.  Observe what happens.  They should begin to separate.  Oil and vinegar do not stay well mixed.

Part 2
1. In a separate bowl, add one teaspoon of vinegar and an egg yolk (you will need to separate it from the egg white first).  Mix these two ingredients together well.
2. Now, add one cup of oil and two teaspoons of vinegar.  Mix the egg mixture together using the whisk or eggbeater.  What happens?  Observe.
3. Discuss your results. 

Emulsions aren’t just an experiment, though – they’re something you can see everyday. In honor of Big Bite Nite tomorrow night, Chef Sandor Edmonson from *17 at the Alden and I whip up a tasty vinaigrette. Click the video below to see the dish in progress as we create great example of an emulsion.

Want to learn how to make more food at home?
Learn the ingredients for ice cream.
Learn how to make your own butter.

Want to see more in the Science of Food video series?
Watch me make ice cream with Quattro’s Executive Pastry Chef Philippe Valladares.
See me make butterwith Adam Puskorius, Executive Chef at Polo’s Signature.


Chemistry in the Kitchen: The Science Behind Ice Cream

Legend has it that the Roman emperor Nero discovered ice cream. Runners brought snow from the mountains to make the first ice cream.

Making ice cream at home is easy – no mountain marathon required! Just read the instructions below and enjoy your very own homemade ice cream.

ice-cream-bowl
 Creative Commons LicensePhoto Credit: Jessicafm

Materials:
Sugar
Milk
Vanilla
Rock salt
Pint-size baggies – heavy duty
Gallon-size baggies – heavy duty
Measuring cup
Measuring spoons
Spoons

Procedure:
1. Fill the large bag about ½ full of ice.  Add 6 tablespoons of rock salt to the ice.

2. Put ½ cup of milk, ¼ teaspoon of vanilla, and 1 tablespoon of sugar into a smaller baggie and seal.  Put this inside another small baggie and seal.  This will prevent saltwater from seeping into your ice cream.

3. Place the double bagged small baggie into the larger baggie and seal.

4. Shake the baggie until you have ice cream. 

5. Remove the smaller baggie from the larger one.  Wipe off the water, then open it carefully and enjoy your ice cream! 

UPDATE: Check out our Science of Ice Cream video to learn more!

Chemistry in the Kitchen: The Science Behind Butter

stick-of-butter
 Photo credit: booleansplit

People have been enjoying the rich and wonderful taste of butter for more than 6,000 years.  Archaeologists have found pounds of ancient butter buried in the peat bogs of Ireland.  Butter is still made in essentially the same way as it has been for thousands of years.  Roll up your sleeves and make butter like the ancients!

Materials:
Heavy whipping cream – you can buy this at the grocery store
Crackers – any kind you like
Salt
Cheesecloth
Clean baby food jar
Butter knife

Procedure:
1. Fill your baby food jar about ½ full with whipping cream.
2. Add a pinch of salt for taste.
3. Seal the cap on tight.
4. Shake your jar up and down vigorously.
5. You will notice that soon you will have a creamy substance that we know as whipped cream.  You’re not done yet!  Keep shaking!
6. Soon you will have a clump surrounded by a liquid.  The clump is your butter and the liquid is buttermilk.
7. Drink the buttermilk if you like, it’s full of protein.
8. Place your butter in a piece of cheesecloth and squeeze the excess liquid out.
9. Use your butter knife to spread your creation on crackers and enjoy!

Background:
When milk straight from the cow is left to stand it separates into skim milk and cream.  The cream rises to the top.  The cream is full of proteins and fat.  When you shake the cream and agitate the fat globules, they stick together to form butter.  The leftover liquid is called buttermilk and it is full of protein. 

Interested in learning more about cooking and the science behind it? BEYONDbones will be bringing you The Science of Food - a series of videos exploring the science involved in the culinary creations of some of the best chefs in town. Its all part of Big Bite Nite on April 30, an event featuring food from over 30 restaurants all in one location – HMNS.