Two reasons:
- Refrigeration wasn’t always as reliable.
- People relied more on smell and visible spoilage signs.
And truthfully, many people got away with it because:
- Homes were cooler.
- They consumed jars faster.
- Cross-contamination was less frequent.
But modern food safety standards are stricter because we understand microbial growth better now.
The Science in Simple Terms
Bacteria multiply exponentially.
At room temperature, some bacteria can double every 20–30 minutes.
After several hours, a small contamination can become millions of cells.
Refrigeration slows growth dramatically.
Cold doesn’t kill bacteria — but it slows them.
That slowing is the safety buffer.
How to Handle Mayo Safely
Here’s the practical rule:
Unopened jar → shelf stable
Opened jar → refrigerate
Left out less than 2 hours → usually fine
Left out 8+ hours → discard
Left out days → discard
It’s not about paranoia.
It’s about risk management.
Trust Your Nervous Feeling
That slight hesitation you feel? That’s risk assessment.
When it comes to food safety, the cost of throwing away a jar is tiny compared to the cost of food poisoning.
Your body will thank you.
Final Thought
Mayonnaise isn’t fragile.
But opened mayonnaise left at room temperature for days is not something you want to gamble with.
If nana insists it’s “always been fine,” she may not be wrong — but probability isn’t certainty.
Food safety is about stacking odds in your favor.
And refrigeration is one of the simplest tools we have.
When in doubt:
Cold is safe.
Warm is risky.
Acid helps — but time matters.
If you want, tell me:
Was it store-bought or homemade?
