A leftover Onion is Deadly?

Botulism: Don't keep Onion leftover

By: Arlene Gentallan

A leftover Onion is Deadly?
A leftover Onion is Deadly?

        Onion has a number of important health benefits, but don't ever keep an already sliced leftover of this pungent vegetable. Leftover onions are not safe! Even sauteed onions left at room temperature for prolong periods can be fatal!

        Hold it right there! Suppose I only need half an onion for my recipe. So I cut an onion into half, cook one half, while I store the other half on the shelf / refrigerator. You mean to say that's fatal?

The facts

Sauteed Onion

        In the year 1983, 28 people were afflicted with botulism after eating patty-melt sandwich containing sauteed onions. Botulism toxin were isolated in the sandwich wrapper.

        Among those 28 individuals, one died 6 months later in the hospital, while 12 others required mechanical ventilation to support their breathing.

Here's another case...

Garlic-infused oil

        In 1989, 3 people were afflicted with botulism after eating garlic bread made from "garlic-in-oil product" which upon later examination, were contaminated with Clostridium botulinum and botulinum toxin.

What to do? The FDA encourages to eat onion containing products fresh from the pan. Storing left over onion at room temperature increases risk of botulism.

What is Botulism?

        Botulism is a rare but deadly disease. It is caused by the bacteria Clostridium botulinum which produces a neurotoxin. This toxin blocks the release of the neurotransmitter acetylcholine which leads to paralysis.

Children and elderly are vulnerable to botulism.

12 - 36 hours after ingestion of contaminated food, botulism symptoms may develop, such as:
  • Nausea / Vomiting
  • Difficulty breathing / swallowing / speaking
  • Drooping eyelids
  • Facial weakness
  • Muscular paralysis

Don't judge an onion by it's looks

        In a study by Austin, Dodds, Blanchfield, and Farber, they were able to detect the deadly neurotoxin produced by Clostridium botulinum in spoiled cut vegetables, that's not the case for onion and butternut squash. Neurotoxin that can cause paralysis is present in onion and butternut squash even when they appear good.

Can refrigeration of onion prevent botulism?

        A study by Austin, Dodds,Blanchfield, and Farber, shows that nonproteolytic Clostridium botulinum can produce the deadly neurotoxin even at 5 degrees C, so they recommend storing fresh-cut vegetables below 5 degrees C to prevent botulism.

I eat leftover onion but I don't get botulism...

        Now, there are people who do keep leftover onion, and eat it later but don't develop botulism. This means eating stored leftover onion don't show up 100% of the time. But hey, I just want to tell you the risks involved...because food poisoning by Clostridium botulinum in onion does occur.

        Remember botulism appears rarely but is often deadly...

Related article: Health Benefits of Onion