Mayonnaise is a common kitchen staple, used both as a condiment and as a key ingredient in countless recipes—from sandwiches and salads to marinades and dips. Yet one question continues to cause confusion in home kitchens and at picnics alike: does mayonnaise need to be refrigerated, or can it safely sit out at room temperature?
The answer matters more than many people realize. Improper storage can increase the risk of foodborne illness, compromise flavor and texture, and significantly shorten mayonnaise’s shelf life. Understanding what mayonnaise is made of—and how it behaves over time—helps clear up the confusion.
The science behind mayonnaise
Mayonnaise is an emulsion, meaning it is a stable mixture of ingredients that would normally separate. Its primary components are oil, egg yolks, and an acid such as vinegar or lemon juice. The egg yolks contain lecithin, a natural emulsifier that allows oil and liquid to bind together into a smooth, creamy consistency.
The acidic element plays an important role in food safety. Acid lowers the pH of mayonnaise, creating an environment that slows the growth of many bacteria. However, this acidity does not make mayonnaise immune to spoilage or contamination. If harmful bacteria are introduced and conditions are favorable—especially warmth—growth can still occur.
Continue reading on the next page…