Mayonnaise is a thick, creamy dressing that consists of egg yolks, oil, vinegar or lemon juice, and seasonings. Mayonnaise is an emulsion colloid. Emulsions are a mixture of two liquids that can’t be combined, for instance, oil and water.
Therefore, mayonnaise is made from the suspension of oil droplets in vinegar (a water-based continuous phase), stabilized by egg yolk molecules having both an oil-soluble and water-soluble end. Mayonnaise shouldn’t be confused with salad dressing, which is sweeter and doesn’t contain egg yolks.
Mayonnaise is an example of a class of colloid called emulsions. An emulsion is a colloid of two or more immiscible liquids where one liquid contains the dispersion of the other liquids. In simpler words, an emulsion is a mixture made by combining liquids that normally don’t mix.
A classic example is mixing oil and water. Emulsification is the process of turning a liquid mixture into an emulsion. Other examples of emulsions besides mayonnaise are butter, egg yolk, and crema on expresso.
The terms colloid and emulsion can be used interchangeably. Whereas both phases of the mixture in emulsions are liquids, the particles in colloids can be any phase of matter, either solid or liquid. Therefore, an emulsion is a type of colloid, but not all colloids are emulsions.
How is Mayonnaise Made?
Being an emulsion colloid, mayonnaise is made in part of oil and vinegar. Vinegar is polar and oil nonpolar, so the two don’t mix. Mixing them would result in the two liquids separating into layers. Adding egg yolk stabilizes the mixture and prevents the separation of the two liquids. Egg yolk acts as the emulsifying agent since it interacts with both the polar vinegar and nonpolar oil.
To make mayonnaise, one combines an aqueous solution (lemon juice or vinegar) with egg yolks. Lecithin is an emulsifier found in eggs that helps to prevent separation by binding the ingredients together. Oil is added drop by drop and the mixture whisked rapidly to make the liquids emulsify.
Not whisking rapidly, or adding the oil too quickly will cause the liquids to separate. However, as the mixture starts thickening, you can add oil more rapidly. Once all the oil has been added, you can whisk in seasonings into your mixture.
Is Mayonnaise Safe to Eat?
Mayonnaise can be easily made at home using a blender, mixers, and food processors. Most people in the gourmet industry prefer homemade mayonnaise to commercial mayonnaise because of its rich taste and consistency.
However, because of the risk of salmonella found in raw eggs, it’s important to use the freshest eggs possible to make your uncooked homemade mayonnaise. Unlike commercial mayonnaise which can last up to six months in the refrigerator, homemade mayonnaise only lasts three to four days.
According to U.S. law, commercial mayonnaise contains at least 65-percent of oil by weight. Laws in the U.S. restrict manufacturers from using other emulsifying agents in making “real mayonnaise”. This law requires them to use egg as the emulsifier in their processes. Reduced-fat mayonnaise use cellulose gel, modified food starch, and other thickeners as emulsifiers.
Tartar sauce and thousand-island salad dressing use mayonnaise as their base whereas aioli is garlic-flavored mayonnaise. Hollandaise is another classic example of an emulsion sauce that’s a cooked mixture of butter, egg yolks, and lemon juice.
Emulsions are colloids where both phases of the mixture are liquids that can’t be normally combined, for example, water and oil. Mayonnaise is an emulsion colloid made from polar vinegar and nonpolar oil emulsified by egg yolk that prevents their separation.
Egg interacts with both the polar and nonpolar ends to stabilize the mixture. Homemade mayonnaise is rich in taste and consistency but can only be stored for a short time compared to commercial mayonnaise.