- How long does mayonnaise last once opened? The precise answer depends to a large extent on storage conditions - keep opened mayonnaise refrigerated and tightly covered at all times.
How long does opened mayonnaise last in the refrigerator? Mayonnaise that has been continuously refrigerated will generally stay at best quality for about 2 to 3 months after the "Best By" date on the package.
How long can opened mayonnaise be left at room temperature? Bacteria grow rapidly at temperatures between 40°F and 140 °F; opened mayonnaise should be discarded if left out for more than 8 hours at room temperature.
Is opened mayonnaise safe to use after the "expiration date" on the package? Yes, provided it has been stored properly, the package is undamaged, and there are no signs of spoilage (see below) - commercially packaged mayonnaise will typically carry a " Best By," "Best if Used By," " Best Before, or "Best When Used By" date but this is not a safety date, it is the manufacturer's estimate of how long the mayonnaise will remain at peak quality.
How can you tell if mayonnaise is bad or spoiled? The best way is to smell and look at the mayonnaise: if mayonnaise develops an off odor, flavor or appearance, or if mold appears, it should be discarded.
Sources: For details about data sources used for food storage information, please click here