Question: How long can I let an opened jar of mayonnaise sit out of the refrigerator before it becomes unsafe to eat?
Answer: You can let an opened jar of mayonnaise sit out at room temperature for up to 8 hours, says the United States Department of Agriculture. Opened mayonnaise that has been held above 50 degrees Fahrenheit for more than 8 hours should be discarded.
An opened jar of mayonnaise that has been continuously refrigerated, on the other hand, will generally maintain best quality for 2 to 3 months after the “best by” date on the package.
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