The jar of mayonnaise in your fridge door hides a surprisingly dramatic story. This episode examines the popular origin tale of the Duke of Richelieu’s 1756 siege of Mahón on Menorca, the evidence that a similar sauce already existed in Spain, from a 1750 Valencian manuscript to 14th century Catalan texts, and the 19th century French naming fight over bayonnaise, magnonnaise, and moyeunaise.

We then crack open the science of emulsion, explaining how lecithin in egg yolk binds oil and water and why tightly packed droplets create a thick gel. From there we follow the commercial rise of mayonnaise in the United States with Richard Hellmann, its central role in Russian and Japanese cuisine, how regulators define it, and the salmonella outbreaks that made acidity and pasteurized eggs essential.

• Why the Mahón story is likely a case of the French adopting an existing local sauce
• How lecithin acts like an adapter plug and how mustard and vinegar help stabilize the emulsion
• How Hellmann went from selling mayo in wooden butter boats to a trademarked brand
• Why mayonnaise outsells ketchup in Russia and how Kewpie changed the formula for Japan
• Deadly outbreaks in Denmark, on flights to Spain, and in a New York hospital, and why pH must stay below 4.1