By the end of this lab, students should know how to make mayonnaise and explain the science behind it.
Background
Some liquids, like oil and water, don’t mix well. When you try to combine them, they separate. This is because they are immiscible, meaning they can’t dissolve in each other. This separation can be a problem when making foods that contain both oil and water, as it can affect the food’s look and quality.
To solve this, we use something called an emulsifier. An emulsifier helps mix these immiscible liquids into a smooth blend known as an emulsion. Creating an emulsion typically involves breaking one liquid into tiny droplets and evenly dispersing it throughout the other liquid. This is usually done with tools like a high-speed blender or homogenizer.
A common example of an emulsion is mayonnaise, where oil is mixed with water. Egg yolk is used as the emulsifier in mayonnaise because it contains a special ingredient called lecithin. Lecithin molecules have two ends: one that likes water (hydrophilic) and one that likes oil (hydrophobic). This allows them to grab onto both water and oil, holding them together in a stable mixture. This dual attraction property is known as being amphiphilic.
Materials and Equipment
- Stainless steel pot
- Stove
- Scale
- Thermometer
- Mixing spoon
- Mixing bowl
- Glass jars
Product Formulation
| Ingredients | Weight (g) | Percentage (%) |
| Vegetable oil | 430 | 86.7 |
| Pasteurized egg | 33 | 6.7 |
| White vinegar | 15 | 3 |
| Lemon juice | 10 | 2 |
| Salt | 6 | 1.2 |
| Sugar | 2 | 0.4 |
| Total | 496 | 100 |
Method
- Pasteurize 2 large eggs in hot water (63oC) for 15 minutes. Note: Make sure to maintain this temperature since higher temperatures will cause coagulation of egg while lower temperatures could prevent adequate pasteurization required for food safety
- Separate pasteurized egg yolks from eggs and weigh out the required amount needed (33 g)
- Add lemon juice
- Add vinegar
- Mix vigorously until a homogenous liquid is achieved
- Gradually add vegetable oil with continuous and vigorous mixing. Note: This can be done by hand but can also be done by a high-speed mixer for greater speed and efficiency. The mayonnaise will thicken as you continue to mix. If it begins to thin to a watery consistency, this is an indication that your emulsion has broken. If this happens, you will have to start over. To avoid this, make sure to add the oil slowly.
- Add salt, spice, and sugar, and mix for another minute
- Bottle in sterilized jars
- Refrigerate
Lab Questions
- What is an emulsion?
- A mixture of two soluble liquids.
- A combination of two immiscible liquids stabilized by an emulsifier.
- A type of chemical reaction between oil and water.
- A process of heating oil before combining it with water.
- Why is mayonnaise considered an oil-in-water emulsion?
- Because it consists mainly of oil.
- Because water is dispersed in oil.
- Because oil is dispersed in a continuous phase of water.
- Because water and oil are both equally present.
- Which component acts as an emulsifier in mayonnaise?
- Vinegar
- Egg yolk
- Mustard
- Salt
- What role does lecithin in egg yolk play in making mayonnaise?
- It thickens the mayonnaise.
- It acts solely as a flavor enhancer.
- It increases the acidity of the mayonnaise.
- It helps bind water and oil, preventing separation.
- How does the structure of lecithin contribute to its function as an emulsifier?
- Lecithin molecules have both hydrophobic and hydrophilic properties.
- Lecithin molecules are entirely hydrophobic.
- Lecithin molecules are entirely hydrophilic.
- Lecithin molecules react chemically with oil and water.
