Do Chopped Onions Attract Bacteria?

Answers

• Onions are mildly antibacterial.
• Chopped onions can be stored in the fridge for a week.
• They have no way of attracting airborne bacteria and getting contaminated.

The Context

Long before bacteria were discovered, people believed that chopped onions left in a room would protect its inhabitants from noxious air, which was the cause of contagious diseases as per the prevailing view of those times.

Even now, many people hold that cut onions attract bacteria from the air, cleaning the room. In the process, the onions become contaminated and can cause food poisoning if eaten. So they think one should not store onion chunks in a refrigerator and never consume them a few hours after chopping them.

The Science

• Onions are acidic, preventing bacterial growth.
• Bacteria usually thrive in high-protein food sources—onions have almost no proteins.
• When onions are cut, a chemical called propenesulfenic acid is formed and slowly converted to sulphuric acid—the compound that makes your eyes water. Cut onion juice has antimicrobial properties and won’t allow bacterial growth.
• Onions can be contaminated by unhygienic handling but not by absorbing airborne bacteria. So onions cannot sanitise a room or become a magnet for bacteria.
• Onions can be chopped and safely stored in a sealed container in a fridge for up to a week. Throw away if they develop mould.

To Read More

• USA Today: Fact check: Leaving raw onions around your house won’t prevent illnesses
• National Onion Association: Onions & Flu
• EatingWell.com: Are Cut, Raw Onions Poisonous?
• Best Food Facts: Do Onions Absorb Bacteria That Cause Illness?

First Published on: 29th April 2023
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