I grow a lot of onions. some for us and some for the market. We end up putting about two hundred pounds in storage every fall.
Store onions in a cool, dark, humid place after they have matured and are fully cured, or gone dormant. The ideal temperature for long-term storage is between 36 and 33 degrees F, common refrigerator temperatures. Humidity should be 50-60 percent. Onions may sprout if temperatures go above 40 F.
How to Store Onions For Winter
Onions can be stored fresh, or they can be frozen, dehydrated, canned, and even pickled to preserve them for future use. Fresh is usually preferred, so let’s talk about that first.
When getting ready to store fresh onions, you should probably first figure out if they are actually storage-type onions. Storage-type onions and storage-ready onions will have the common papery, dry skin to them. Some onions are fresh and don’t have that leathery paper skin yet and some are a variety that will simply never develop it.
Fresh onions are prepped for storage by ‘curing’. That means allowing the bulb to develop the dry skin and go into the mature dormant stage. The onion is still technically alive but it will be dry and hard on the outside.
The outer layers don’t just dry out, they completely change their structure to withstand air and retain moisture. I cure mine by pulling them and leaving them in the field for a week or two to sun-cure.
That’s how it’s usually done around here but in hotter regions where the temperature can be over 94 or 95 F, it’s recommended not to leave them in the sun. Instead, they are cured under a roof on racks or in wire baskets.
When they’re ready for storage, my best advice is to keep them cold and dry, but humid. They should never be able to get wet or have condensation, so a moderately consistent temperature is important. Honestly, a refrigerator would work well if dedicated for the purpose of storing onions.
If it’s not opened often, the onions will be pretty dry yet humid. Just don’t over fill a home-model refrigerator or you will get freezing. If they do freeze, onions should be peeled and kept frozen until needed for use.
Store them out of sunlight to preserve their color and prevent greenness from developing on the bulbs. Sunlight also tends to warm them more than preferred, so just keep them out of the light best you can.
Make sure your onion storage area has good airflow. A pantry that’s tightly closed and seldom opened can cause increased growth of molds and mildews from low levels of natural condensation. Refrigerators have their own ventilation built-in.
How to Freeze Onions
Freeze onions that are peeled and chopped or diced as you would use them. Place your chopped onion in quart or smaller sized freezer bags and lay them flat in the freezer. When you take it out of the freezer, use it immediately or keep refrigerated for a few days until needed. Water usually leaks out of the bag after thawing, so place it in a dish or bowl.
My wife likes to freeze onions. You really aught to dice onions before freezing because after thawing, they will be mushy and not chop or dice well. They’re also messier after thawing. They will be soft and soggy, so only freeze onions that you are going to cook with. They just aren’t very nice for fresh eating at that point.
Onion smell will somehow escape from your freezer bags and if you have a lot of them in your freezer, the whole thing will smell like onions. That’s how it is, so don’t freeze onions next to fruits and ice cream.
Frozen onions can taste a little bit different, but they end up very satisfactory after being cooked into any recipe. I’ve certainly got no complaints. They cook faster than raw onion, but won’t carmelize the same way.
It can help to blanch them first. That is, scald them in simmering water until they soften a little right through to the center of the onion. It takes about five minutes, plus or minus. Blanching tends to help to preserve the quality of an onion after thawing.
How to can Onions
Onions can be canned by common methods, but it is recommended to be pressure canned. Onions are usually chopped or sliced, then pressure canned at 10 pounds for 40 minutes. They can be canned fresh or cooked. My wife likes to blanch them before canning.