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June 2022

Onions by Joseph Mucira from Pixabay
Onions by Joseph Mucira from Pixabay
Onions (Allium cepa) are a member of the same family as garlic, leeks and shallots. The common bulb onion is a succulent vegetable composed of layers of fleshy modified leaves. They are often grouped by color (yellow | red | white) or taste (mild/sweet | strong/pungent). Generally, sweet onions don't store as well as pungent varieties. Raw or cooked, they add flavor, color and texture to food dishes.

Excerpts from New Mexico State University, Healthy Facts about Onions Onions not only provide flavor; they also provide health-promoting phytochemicals as well as nutrients. Onions are a source of vitamin C, potassium, dietary fiber and folic acid. They also contain calcium, iron and have a high protein quality (ratio of mg amino acid/gram protein). Onions are low in sodium and contain no fat.

Fresh bulb onions are available in southern California markets from about May through December.

Continue reading this page for tips on using and safely preserving onions at home. Visit linked source pages for additional information.

NOTE: Research on food preservation is ongoing - recommendations may change. Make sure your preservation information is always current. Always follow up-to-date, tested guidelines and recipes from reliable sources

Fresh Onions

from South Dakota University State Extension, Onion: Pick it, Try it

Onions are yellow, red or white. 

  • Yellow onions: full flavored, work in most cooking. When cooked, they become sweeter and turn brown.
  • Red onions: used fresh or grilled.
  • White onions: used in classic Mexican cuisine.

from University of Illinois Extension, Watch Your Garden Grow, Vegetable Directory: Onion

Why do onions make you cry? When you cut into an onion, the cell walls are damaged releasing a sulfur compound called propanethial-S-oxide which floats into the air. This compound is converted to sulfuric acid when it comes in contact with water which is why it stings your eyes. Chilling inactivates the propanethial-S-oxide so it does not float into the air. Thus, no tears.

  • To keep eyes dry when chopping onions, try chilling peeled onions in the refrigerator before chopping.
  • To get the onion smell off your hands, rub with lemon juice or vinegar.
  • To freshen onion breath, chew a little parsley or a coffee bean.

Excerpts from Ohio State Extension, Selecting, Storing and Serving Ohio Onions

Selection - Select bright, clean, hard, well-shaped onions with dry skins that crackle. Do not select onions with a thick, woody, tough or open condition of the neck or those with the presence of a stem—these are indicators of seed stem development. Moisture at the neck is an indication of decay. Onions should be free from green sunburn spots and other blemishes.

Storage - Store onions in a cool, dry, dark place to prevent sprouting and decay. Be careful not to bruise them. Be sure to cure onions to harden and dry the outer scales before you store them. Cured onions can be stored in loosely woven or open-mesh containers for several months.

Do not wash before storing.

Preparation and Serving - Wash onions just before [use]. Remove outer layers that may hold soil. Wash onions thoroughly in cold water to remove dirt. Do not use soap, detergent, or bleach because these liquids absorb into the vegetable.

Onions can be added to many dishes, both fresh and cooked. 
Caramelize onions by heating over low heat with oil to achieve the desired color and consistency.
Onions may also be served creamed, scalloped, au gratin, fried, baked, stuffed, sliced, or deep-fried.

Follow food safety guidelines (CLEAN - SEPARATE - HEAT - CHILL) when preparing ingredients, cooking and serving food, and storing leftovers.

Refrigerating and Freezing Onions

Sweet onions may last longer when stored in a refrigerator crisper drawer with each bulb onion wrapped individually in a dry paper towel.

Once an onion is cut, the unused portion should be sealed and stored in the refrigerator at 40°F or below. Sliced or diced onion will keep in the refrigerator is days. Freezing at 0°F or below, onions last much longer; use within months for best quality.

Sliced or Diced Onion can be frozen without blanching. Freezing changes the texture of an onion, making it unsuitable for raw usage. Measure, no thawing necessary, for use in cooked dishes.

Excerpt from University of Nebraska - Lincoln, How to Freeze Onions

  • Dry Pack - Pour onions in freezer bags. Placing packages flat in the freezer helps the onions to freeze faster and makes it easier to break off sections as needed. Express out the air and place bags on cookie sheets or metal pans until onions are frozen. Then, restack bags to take up less room.
  • Tray Pack - Freeze onions in a single layer on a clean cookie sheet with sides, about an hour or longer until frozen prior to packaging. Transfer to a freezer bag when frozen, excluding as much air as possible from the bag. The onions will remain separated for ease of use in measuring out for recipes.

Excerpts from National Center for Home Food Preservation, Freezing Onions
adapted from "So Easy to Preserve", 6th ed. 2014. Bulletin 989, Cooperative Extension Service, The University of Georgia, Athens. Revised by Elizabeth L. Andress. Ph.D. and Judy A. Harrison, Ph.D., Extension Foods Specialists.

Freezing is usually not recommended for preserving whole onions, but see below if desired.

Whole Bulb Onions - Choose mature bulbs; peel, trim and clean thoroughly as for eating. Water blanch for 3 minutes (smaller onions) to 7 minutes (larger onions) or until center is completely heated. Cool promptly, drain well, and package, leaving 1/2-inch headspace. Seal and freeze. These would be considered suitable for cooking only.

Onion Rings - Wash, peel and slice onions. Separate slices into rings. Water blanch for 10 to 15 seconds. Cool promptly, drain and coat with flour. Dip in milk. Coat with a mixture of equal parts cornmeal and pancake mix. Arrange in a single layer on a tray. Freeze. Pack into containers using plastic wrap to separate the layers. No headspace is necessary. Seal and freeze. To prepare, fry frozen rings in 375ºF oil until golden brown.

Drying Onions

"Consider when and where you dry onions because the odor will permeate the house." from Penn State Extension, The Well Preserved Onion

Drying Vegetables, MontGuide MT200907HR is a self-learning resource from Montana State University Extension. Below are some excerpts chosen from the 2017 revision. Please refer to the full document for additional details about drying onions and other vegetables.

Food drying is one of the oldest methods of preserving food and is simple and easy to learn. Drying removes moisture from food so that bacteria, yeasts, and molds cannot grow and spoil food. Making safe dry foods requires cleanliness in every step, protecting the food from airborne spoilers and other contaminants, and using food-grade containers, equipment and ingredients.

Vegetables can be dried in a food dehydrator or in an oven by using the right combination of warm temperatures, low humidity and air current. The optimum temperature for drying food is 140°F. If higher temperatures are used, the food will cook instead of drying, causing a greater likelihood of food molding. Low humidity aids the drying process. If the surrounding air is humid, then drying will be a slower process. Increasing the air current speeds up drying by moving the surrounding moist air away from the food. Most foods can be dried indoors using modern food dehydrators or conventional ovens.

Onions Preparation - Wash and remove outer 'paper shells'. Remove tops and root ends, slice 1/8 to 1/4-inch thick. No blanching needed.

Drying Onions - Estimated drying time in a dehydrator is 3 to 9 hours.
Vegetables should be dried until they are brittle or “crisp.”

Storing Dried Onions - Store in a dark, dry, cool place. Low temperatures extend the shelf life of the dried product. Most dried vegetables can be stored for 1 year at 60°F, 6 months at 80°F.

Vacuum sealing foods can increase the shelf life of some foods, but it is NOT a food preservation method by itself. If the food required refrigeration or freezing before vacuum sealing, it must still be kept refrigerated or frozen. Essentially vacuum sealing removes oxygen. Lower levels of oxygen helps reduce food spoilage. But on the other hand, this reduction in oxygen increases the risk of botulism, a potentially deadly foodborne illness caused by a bacteria that grows best when oxygen is removed during vacuum sealing.

Using Dried Vegetables - Cover dried vegetables with cold water and let them soak until they are nearly restored to their original texture (1⁄2 to 2 hours). If they are soaked longer than two hours, the vegetables should be refrigerated. Using boiling liquid speeds up the soaking time. Save and use the soaking liquid in cooking.

When using dried vegetables in soups and stews, add them without soaking and they will rehydrate as they cook. Add enough water to keep them covered and simmer until tender.

Canning Onions

We recommend that you follow a research-tested recipe and the USDA-approved procedures when canning.

If you are new to canning or want a review of the principles of home canning or the steps to safely canning at home, read Chapter 1 of USDA "Complete Guide to Home Canning", 2015. University of Wisconsin-Madison Extension has published An Update on Use of Steam Canners, August 18, 2020.

adapted from PennState Extension, The Well Preserved Onion

As a low acid vegetable, onions must be pressure canned to avoid the potential of botulism poisoning. Directions for pressure canning onions that are 1-inch in diameter or less are from the Michgan State University Extension article "Onions: Those Versatile Edible Bulbs".

The following recipes contain adequate vinegar to increase the acidity, so it is safe to process them in a boiling water bath or atmospheric steam canner. They feature onion as the main ingredient. The finished products can be used stand alone as a relish or pickle; they make a tasty addition to sandwiches or as an accompaniment to meats. When fresh onions are not available, stir pickled onions into potato or macaroni salad.

Pickled Pearl Onions 

Pickled Onions - tiny onions
Recipe is in the University of Wisconsin Cooperative Extension publication B2267 (R05-2008), "Homemade Pickles and Relishes" on page 34.

Onion Relish - pickled sliced onions
Recipe is toward the bottom of the PennState Extension page, The Well Preserved Onion. It is credited to "So Easy to Preserve" cookbook by the University of Georgia Cooperative Extension.

Vidalia Onion Relish - ground sweet Vidalia onions
Recipe is in the University of Georgia Extension publication (FDNS-E-43-18, 0415), "Canning Relishes" on page 8.

Pickled Pepper Onion Relish - pickled chopped onion and chopped peppers