What's the biggest mistake in onion preservation?
Written by
Benjamin Miller
Reviewed by
Prof. Charles Hartman, Ph.D.Washing onions before storage. Probably the most destructive preservation error. Moisture destroys those layers of protective, papery scales that have been developed during curing, activating all rot pathogens within hours and ruining weeks or months of the grower's effort and work.
Barrier Destruction
- Water dissolves antimicrobial compounds in outer skins
- Disrupts waxy cuticle that seals the neck
- Creates microscopic cracks for pathogen entry
Moisture Trapping
- Liquid pools between skin layers
- Increases bulb humidity to 90%+
- Activates dormant botrytis spores
Correct Alternative
- Dry-brush soil after 2-week curing period
- Use soft-bristle brush in downward strokes
- Focus on root area without damaging basal plate
Natural antimicrobial barriers form during proper curing, including allicin compounds and phenolic resins in papery skins. Water immersion washes away those defenses. I learned this the hard way when I had 50 pounds of washed onions mold in my cellar. Now, I only do a dry brush.
Handle dirty onions correctly. Cure thoroughly before sorting these dirty onions with the rest. Allow them to cure for 2 weeks, if possible, and then dry the necks so that they snap off sharply. Cure them, too, in mesh bags so that the natural defence barrier is kept intact against the advance of fungi and bacteria. Storage temperature is 35 to 40°F (65 to 70% humidity).
An ounce of prevention is worth a slice of the cure. Once washed, onions can never be re-cured. Their storage cells will absorb too much moisture. Yet, they can be harvested from dirt, rain, or wind-swept soil in perfect condition if you grow them to the lifting stage and use a garden fork to help lift the bulbs out of the ground.
Read the full article: When to Harvest Onions: Ultimate Guide
