Book 9, Question 3
Why Does Mayonnaise Stay Creamy When Oil and Water Usually Split?
Mayonnaise stays creamy because egg yolk has emulsifiers that hold oil and water together! Oil and water usually push apart, but emulsifiers grab both of them. Tiny oil droplets stay spread out instead of separating.
More fun facts
- Left alone in a jar, water molecules bunch together and oil molecules bunch together, making two layers.
- To mix oil and water, you make an emulsion, spreading tiny drops of one liquid through the other.
- An emulsifier surrounds tiny oil droplets. One end grabs the oil and the other end faces the water.
- Mayonnaise uses a molecule called lecithin from egg yolks as its emulsifier.
- A shaken oil and vinegar dressing is an unstable emulsion and separates if it sits too long.
- Adding mustard can help a salad dressing stay mixed.
Sources: Smithsonian Magazine, BBC
Questions kids ask
Do oil and water ever mix?
Yes, with a little help. An emulsifier like egg yolk lets them stay mixed.