1. Why Water and Oil Separate When You Shake Them
If you put water and oil in a bottle and shake it, they look mixed for a moment. But if you let it sit, they quickly separate into two layers again. This happens because water particles attract each other strongly, pushing the oil particles away. This basic separation is what makes making mayonnaise seem like a mystery.
2. How Egg Yolk and Lecithin Join Water and Oil
Mayonnaise uses egg yolk, the yellow part of the egg. Egg yolk contains a substance called lecithin. Lecithin acts as a bridge because it can get along with both water and oil. It wraps oil into tiny particles inside the water. This prevents the oil particles from sticking together and separating. This process is called emulsification. By adding oil slowly while mixing vigorously, the oil stays in fine particles, creating the thick texture of mayonnaise [1].
3. Where the Name Mayonnaise Comes From: The Story of Mahon
There is a famous story about where the name "mayonnaise" comes from. In 1756, the French army attacked the port town of Mahon on the island of Menorca, which was then British territory. The Duke of Richelieu, who led the army, ate a sauce made with eggs, oil, and lemon juice at a restaurant in Mahon. He liked it very much. When he introduced this sauce in Paris later, it is said he called it "Mahon sauce." This is believed to be the origin of the name mayonnaise [2]. However, this is considered the most likely theory among several origin stories. It is not proven as a definite historical fact.
4. How Nakajima Toichiro Brought Mayonnaise to Japan
The first person to sell mayonnaise in Japan was Nakajima Toichiro. When he was young, he stayed in America for work. There, he saw people putting mayonnaise on their salads. He noticed its high nutritional value. In March 1925, Nakajima manufactured and sold mayonnaise in Japan for the first time [3]. However, sales in the first year were only 120 boxes (600 kilograms). At that time, the word "mayonnaise" was not known. Some people even mistook mayonnaise for hair pomade [3].
5. What Japan's JAS Rules Say a Mayonnaise Must Contain
Japan has rules about what can be called "mayonnaise." According to the JAS (Japanese Agricultural Standard), a product must contain at least 65% edible vegetable oil by total weight to be called mayonnaise [1] [4]. Products with less oil are sold under different names, such as "mayonnaise-type seasoning."
6. Why Homemade Mayonnaise Sometimes Separates
When you make mayonnaise yourself, it sometimes separates into watery and oily parts. This can happen if you add too much oil at once. The egg yolk cannot wrap all the oil particles. The oil particles stick together and grow larger. Then, the mixture returns to being separate water and oil. To prevent this, you must add oil little by little while mixing well.
7. Home Activities to Learn More About Water, Oil, and Mayonnaise
If you want to learn more, try these activities with an adult. First, put water and oil in a bottle and shake it. Watch what happens after a while. Next, look at the ingredient list on a bottle of mayonnaise in your home. See what is written there. Finally, write down one word you are curious about. For example, "Does lecithin appear in other foods?" This can help you start your research.
Safety note: If you try making mayonnaise by hand, do it with an adult. Use fresh eggs. Eat it immediately after making it; do not store it. Always follow safety precautions with an adult.