How Long Does Mayonnaise Last After Opening? (Store-Bought & Homemade)

Opened store-bought mayonnaise lasts up to 2 months in the refrigerator. This is significantly longer than most people assume — mayo's combination of acid (vinegar or lemon juice), salt, and pasteurized eggs creates an environment that strongly inhibits bacterial growth. Homemade mayonnaise is a different story: without preservatives or pasteurization, it lasts only 1 week in the fridge. Unopened commercial mayo is shelf-stable and lasts 3 to 4 months past the best-by date stored in a cool pantry.

Table of Contents

• How Long Does Opened Mayo Last?
• How Long Does Unopened Mayo Last?
• Homemade Mayonnaise vs. Store-Bought
• How to Tell If Mayo Has Gone Bad
• How to Store Mayonnaise Properly
• Quick Reference Summary
• Frequently Asked Questions (FAQ)
• References

How Long Does Opened Mayo Last?

The 2-month window for commercial mayo surprises most people. This is because commercial mayo is made with pasteurized eggs and contains acid (pH around 3.6–4.0) and preservatives like calcium disodium EDTA that collectively make it highly inhospitable to bacterial growth — including Salmonella.

How Long Does Unopened Mayo Last?

Commercially produced mayo does not require refrigeration before opening due to its low pH and preservatives. Many manufacturers recommend refrigerating after opening to maintain quality — not for safety reasons per se, but because flavor and texture hold better at colder temperatures.

Homemade Mayonnaise vs. Store-Bought

Homemade mayo is made with raw eggs, which carry a Salmonella risk at room temperature and break down faster even refrigerated. Use pasteurized eggs if possible when making mayo at home, and use within 1 week regardless.

How to Tell If Mayo Has Gone Bad

Smell: fresh mayo smells tangy, eggy, and slightly fatty. Spoiled mayo smells rancid, sour beyond normal tang, or develops an unpleasant chemical odor from fat oxidation. Rancid mayo is the most common spoilage mode.

Color: fresh mayo is white to pale cream. Yellowing or browning — especially at the surface — indicates fat oxidation and quality loss. A distinctly yellow or gray tinge signals it's past its prime.

Texture: mayo should be smooth and thick. Separation (oil pooling on top) that doesn't reincorporate with stirring, or a watery layer beneath the mayo, indicates breakdown of the emulsion — a sign of spoilage or freezing damage.

Mold: any fuzzy growth means discard the entire jar.

How to Store Mayonnaise Properly

• Always refrigerate after opening — store at 35–40°F (1.5–4°C)
• Store at the back of the refrigerator, not the door
• Use a clean utensil every time — never double-dip a knife or spoon that has touched other foods
• Keep the lid tightly sealed after each use
• Do not leave mayo-dressed dishes at room temperature for more than 2 hours (1 hour above 90°F)

Common mistake: leaving a mayo-dressed salad or sandwich filling out for extended periods. The mayo itself is resilient, but ingredients mixed into it (chicken, eggs, vegetables) can introduce bacteria that multiply quickly at room temperature.

Quick Reference Summary

Frequently Asked Questions (FAQ)

Does mayo go bad faster in the summer? Mayo left out at room temperature degrades faster in heat — and in summer conditions, the 2-hour room temperature rule is even more critical. Refrigerated mayo is unaffected by outdoor temperatures as long as your fridge stays at 40°F or below.

Can you eat mayo that has separated? Minor separation that reincorporates when stirred is usually fine — it's an emulsion stability issue, not spoilage. If stirring doesn't bring it back together and the smell is off, discard.

Is it safe to make mayo with store-bought pasteurized eggs? Yes. Pasteurized shell eggs significantly reduce the Salmonella risk of homemade mayo. Even with pasteurized eggs, homemade mayo lacks commercial preservatives, so the 1-week fridge window still applies.

Why does my mayo sometimes turn yellow? Yellowing is typically fat oxidation — a quality issue rather than a safety issue in early stages. Mayo that is slightly yellow but smells normal is usually still safe. Mayo that is yellow and smells rancid should be discarded.

Can I freeze mayo? Not recommended. Freezing breaks the emulsion — thawed mayo becomes watery, grainy, and separated. It cannot be fully reconstituted. Use within the refrigerator window instead.

References

• USDA Food Safety and Inspection Service. Condiments: Safe Handling
• FDA. Cold Food Storage Chart
• USDA FoodData Central. Mayonnaise products
• Hellmann's / Best Foods. Product FAQs — Storage. https://www.hellmanns.com