Mayonnaise

An emulsion, technically

Mayonnaise is a stable oil-in-water emulsion — tiny oil droplets suspended in a water-based egg yolk matrix, kept stable by the lecithin in the yolk acting as an emulsifier. This is genuinely difficult chemistry; the oil and water want to separate but the egg lecithin prevents it.

This is why mayonnaise can “break” — if oil is added too fast or temperatures are wrong, the emulsion fails and the oil separates out.

Regional formulations

What “mayonnaise” tastes like varies dramatically:

• American (Hellmann’s/Best Foods) — relatively neutral, slightly tangy
• Japanese (Kewpie) — uses only egg yolks (not whites), rice vinegar, and added MSG; richer and sweeter
• Spanish (or “alioli”) — heavy with garlic
• French — often with mustard, sharper, less sweet
• Russian/Eastern European — used in massive quantities in salads (Olivier, herring under fur coat)

The cold-storage myth

The persistent myth that mayonnaise causes food poisoning at picnics is mostly false. Commercial mayonnaise’s high acidity and salt content make it actually inhibitory to bacterial growth. Studies have found that potato salad and chicken salad spoil less quickly with mayonnaise than without.

The real picnic risk is the protein (chicken, eggs, potatoes), not the mayo coating it. Homemade mayonnaise from raw eggs is a different question and can carry salmonella risk.