Mayonnaise that has been opened needs to be stored in the refrigerator. Unopened mayonnaise does not need to be stored in the refrigerator.
Mayonnaise that sits out at room temperature can spoil. Spoiled mayonnaise can cause foodborne illness and develop a sour taste. Vinegar is added to mayonnaise to help prevent the development of bacteria, which can cause illness.
The origin of mayonnaise is debated, but it is believed to have most likely originated in France. The first mention of mayonnaise appeared in the early 1800s.
Mayonnaise is a condiment that is usually white or cream in color. It can be made with or without eggs.