Refrigerate or Leave Out? The Truth About Mayonnaise Storage
Mayonnaise is one of those foods people often wonder about: Does it really need to stay in the refrigerator, or can it safely sit on the counter? The answer depends on whether the jar is opened and how long it has been at room temperature.
Unopened Mayonnaise
An unopened, commercially produced jar of mayonnaise can generally be stored in a cool, dry pantry until its expiration or best-by date, as long as the label doesn’t specify otherwise. Once opened, refrigeration is recommended.
Opened Mayonnaise
After opening, keep mayonnaise refrigerated at 40°F (4°C) or below. Refrigeration slows bacterial growth and helps maintain the product’s quality.
What If It Was Left Out?
Don’t assume mayonnaise is safe simply because it looks or smells normal. Perishable foods should generally not remain at room temperature for more than 2 hours, or 1 hour when temperatures are above 90°F (32°C). This is particularly important for mayonnaise-based salads containing eggs, chicken, tuna, or other perishable ingredients.
If an opened jar has been sitting out for several hours, especially in a warm kitchen, the safest choice is to discard it rather than taste-test it.
Why Does Store-Bought Mayonnaise Last So Long?
Commercial mayonnaise is formulated with ingredients such as vinegar or lemon juice and is manufactured under controlled conditions. These factors make it more resistant to spoilage than many homemade versions. However, that does not mean an opened jar should routinely be stored at room temperature.
What About Homemade Mayonnaise?
Homemade mayonnaise deserves extra caution because it may contain raw eggs and doesn’t have the same commercial processing and formulation. Keep it refrigerated and use pasteurized eggs when appropriate.
The Simple Rule
Unopened commercial mayonnaise: Pantry storage is generally fine if the label allows it.
Opened mayonnaise: Refrigerate it.
Left out for several hours: When in doubt, throw it out.
Homemade mayonnaise: Keep refrigerated and handle carefully.
The refrigerator isn’t just about keeping mayonnaise tasting fresh—it also helps reduce the risk of foodborne illness once the container has been opened.
