Get Emulsified!

Research Questions:

• What happens when you mix oil and water?
• What happens when you add some egg yolk to the mixture of oil and water?
• What is an emulsion?
• What is an emulsifier?
• What is lecithin? How is it used?
• What are some common foods that contain emulsifiers?
• Examine the labels of some “smooth” and “creamy” ice creams. Are there any emulsifiers in these products?
• Examine the labels on mayonnaise. Are there any emulsifiers added?
• Compare “natural” peanut butter and regular peanut butter. Are there any emulsifiers in these products?
• How do soap molecules act as emulsifiers?
• Check out face creams and hand lotions. Are there any emulsifiers present?

On the information level, this experiment serves to acquaint students with basic information about the role of emulsifiers in the chemistry of foods, medicine, soaps and cosmetics. Students will make peanut butter with an emulsifier, and they'll make two kinds of mayonnaise: one with an emulsifier and one without an emulsifier. Taste testers will attempt to use their senses to identify which version of peanut butter and mayonnaise contained an emulsifier and provide the reasons for their choices. The student will use the scientific method in conducting the research and in collecting, analyzing, and summarizing the data in a final report. Students will also compile a bibliography of references utilized in the process of conducting the research.

All of the materials required may be purchased from the local supermarket and obtained from the home kitchen. For your homemade peanut butter, you will need a large package of unsalted roasted peanuts, peanut oil, a bowl, a mixing spoon, a storage container, measuring cups and spoons, and a food processor. For your taste comparison, you will need to purchase a large jar of low fat, low salt peanut butter (such as Jiff). For making your own mayonnaise (two different kinds), you will need 4 eggs, salt, powdered mustard, sugar, cayenne pepper, lemon juice, olive or salad oil ,water, a food processor or mixer, one dozen small paper or plastic cups, and plastic spoons.

Experimental Procedure:

1. Gather all of the materials you will require for this project. You may wish to include a camera and take photos of the process of making your own peanut butter and two different batches of mayonnaise.
2. Reproduce the Data Chart provided below to record your testers' observations. You may wish to reproduce a response sheet for your testers to use. A response sheet is also provided below.
3. Wear your safety glasses and apron.
4. State your hypothesis. What do you predict? Will the samples that contain the emulsifiers taste smoother and creamier than those that do not?
5. Start by making a large batch of peanut butter by using the following recipe. 
   • Take 3 cups of unsalted roasted peanuts and 2 tablespoons of peanut oil. Mix together and pour the mixture into the food processor or the blender. Process the mixture until it is very smooth. Store your smooth peanut butter in a sealed container in the refrigerator.
6. You are now going to prepare two different kinds of mayonnaise. The first type will contain an emulsifier, namely egg yolks which contain lecithin, and the second batch which will contain the same ingredients except you will eliminate the egg yolk and only use the white (the albumen) of the eggs. For type 1 mayonnaise, line up 2 egg yolks, ¾ teaspoon salt, ½ teaspoon powdered mustard, 1/8 teaspoon sugar, a pinch cayenne pepper, 4 teaspoons lemon juice or white vinegar, 1-1/2 cups olive or salad oil, and 4 teaspoons of hot water.
7. Start by beating the yolks, salt, mustard, sugar, pepper, and 1 teaspoon of lemon juice in a small bowl until very thick and pale yellow. If you are using an electric mixer, use medium speed. Add ¼ oil, drop by drop beating all the while. Add 1 teaspoon lemon juice and hot water. Now add ¼ cup oil, a few drops at a time, and beat. Now add ½ cup of oil, then mix in the remaining lemon juice and water, slowly beating in the remaining oil. You should end up with 1-1/2 cups of mayonnaise.
8. If you are using the blender or processor, place yolks, salt, mustard, sugar, pepper, and 3 teaspoons lemon juice in blender cup or work bowl of a food processor fitted with the metal chopping blade, and blend for 15 seconds (use low blender speed). Now, with motor running, slowly drizzle in 1/4 cup oil (use moderately high blender speed). As mixture begins to thicken, continue adding oil in a fine steady stream, alternating with hot water and remaining lemon juice. Stop motor and scrape mixture down from sides of blender cup or work bowl as needed. Place in storage container and refrigerate.
9. Now repeat step 6 or step 7 but substitute egg whites for egg yolks. You are removing the emulsifier from the mayonnaise. Place this second batch of mayonnaise in a storage container and refrigerate. 
10. Obtain 10 of your classmates or friends to be your testers of the each of your batches: the peanute butter you made and the one you bought, and the two mayonnaise samples. Have them record their results. Use the small plastic cups and spoons. Which samples tasted better? How did they differ in taste? Do emulsifiers really make a difference? Were the ones containing emulsifiers smoother or creamier?
11.  Write up your report. Was your hypothesis confirmed? Make certain to include all of your answers to the research questions, your bibliography, and any photos you may have taken of the process of making the peanut butter and the two types of mayonnaise.

Student Response

Subjects' Responses

Terms/Concepts: mixture; solution; solvent; solute; suspension; colloid; emulsion; emulsifier

References:

• http://en.wikipedia.org/wiki/Emulsion
• http://www.understandingfoodadditives.org/pages/Ch2p2-2.htm