Introduction
Wow, I’m only learning this now. My nana has always kept mayonnaise right on the kitchen counter, no fridge involved—and she’s been doing it for decades. Meanwhile, I’m standing there wondering if a sandwich is about to send me into a food-safety crisis. Is mayonnaise really safe to leave out for days, or is this one of those “grandma survived, but science disagrees” situations? Let’s clear up the confusion once and for all.
Ingredients
This isn’t a cooking recipe, but it helps to understand what’s inside mayonnaise:
Oil
Egg yolks (or pasteurized egg products)
Vinegar or lemon juice
Salt
Preservatives (in commercial mayonnaise)
These ingredients—especially the acid—play a huge role in how mayonnaise behaves outside the fridge.
Instructions (How to Store Mayonnaise Safely)
Check the label first
Commercial, store-bought mayonnaise is made with pasteurized eggs and acids, which makes it much more stable than homemade versions.
Unopened jars are different
Unopened commercial mayonnaise can safely sit at room temperature until the expiration date printed on the jar.
Once opened, refrigeration matters
After opening, mayonnaise should be refrigerated and kept at or below 40°F (4°C).
Counter time has limits
Opened mayonnaise should not sit out for more than 2 hours (or 1 hour if it’s very warm).
Homemade mayonnaise is riskier
Because it often contains raw eggs and fewer preservatives, homemade mayo should always be refrigerated and used within 3–4 days.
Serving and Storage Tips
Always use a clean utensil to scoop mayonnaise—double dipping introduces bacteria.
Close the lid tightly after every use to prevent contamination.
Store mayo in the coldest part of the fridge, not the door.
If it smells sour, looks separated, or tastes “off,” throw it out immediately.
Variations (Why Nana’s Mayo Might Have Been Fine)
Older recipes: Some traditional mayonnaise recipes used higher vinegar ratios, making them more acidic and shelf-stable.
Climate matters: Cooler kitchens reduce bacterial growth.
Short-term use: If Nana went through the jar quickly, there may not have been enough time for spoilage.
Miracle Whip vs. mayonnaise: Salad dressings with extra sugar and acid last longer than true mayonnaise.
FAQ
