How to Tell if Mayo Is Bad

• Avoid mayonnaise that has mold growing on it. You can also tell it has spoiled if it is yellow or brown in color.
• Even if your mayo looks okay, check for any acidic, sour, or bitter tastes and smells to be sure it has not gone bad.
• Unopened mayonnaise is likely to last for up to three months after its "best by" date. Open mayonnaise can last in the fridge for about two months.

How to Tell if Mayonnaise is Bad

The mayo has mold on it. Green, blue, or black spores should not be on or near your mayonnaise. Before using the mayo in question, check for noticeable signs of mold by examining the top layer of the spread inside the jar and along the jar’s outside. If you find even the smallest amount of mold, toss it out. Take the mayo label off the jar to get a better look at what’s going on inside.

The mayo is yellow or brown. Usually, mayonnaise is an off-white color. If you look in the jar, and the mayo appears to be more on the yellow side leaning towards brown, it’s most likely spoiled.

The mayo smells acidic or putrid. Mayonnaise doesn’t have much of a smell, so if you open that jar and are hit with a strong sour odor, it’s bad. Screw back on the lid and throw it out.

The mayo tastes sour or bitter. Dip the tip of your finger in the questionable mayonnaise and take a small lick. If it tastes strange or “off,” toss it out.

How long does mayo last?

Mayonnaise can last unopened 2 to 3 months after the “best by” date. This means that it's most likely still good if you have an unopened jar in your fridge or pantry. However, it’s always best to double-check for spoilage before you eat anything past the “best by” date. The “best by” or “use by” date refers to when the mayo has the best flavor or quality. The number of preservatives in your mayo also plays a factor as the egg yolks used to make the spread are perishable.

Opened mayonnaise lasts about 2 months in the fridge. If you just opened the jar, chances are it’s still good! If you can’t remember when you first opened it, check for signs of spoilage before making that potato salad.

Opened mayonnaise can’t last more than 8 hours on the counter. Harmful bacteria can get inside the mayo when it’s been left at room temperature for too long, causing it to spoil faster. It’s always recommended to place products with perishable ingredients, such as egg yolks, back in the fridge after opening and using.

Homemade mayonnaise only lasts for an average of 7 days in the fridge. Making mayo can be a great and fun alternative to buying large batches of processed mayonnaise! But there is a downside: it doesn’t last nearly as long. With a lack of preservatives, the eggs and dairy in homemade mayo spoil faster. Some cooks and homesteaders recommended using homemade mayo within 2 to 3 days of making, while others suggest it can last 7 to 10 days before spoiling.

How to Store Mayonnaise

In the fridge Once you open a jar of mayo, keep it in the refrigerator so it doesn’t spoil. Most mayonnaise contains egg yolks, and needs to be chilled to stay preserved.

In the freezer Mayonnaise can be frozen before its “best by” date, but it will change in appearance and consistency. Frozen mayo needs to be thawed before using, and this can result in a yellow, watery spread. The changes that happen to mayo after freezing and thawing do not mean it’s gone bad. The acidic ingredients and oil simply separate in a freezing temperature.