January 3

Can You Freeze Onions? Yes, Here’s How

Written by: Caitlin Clark


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Onions are ubiquitous in nearly all of the world’s cuisines. They are a member of the Cajun holy trinity, they make up part of a French mirepoix, and you’ll find them in nearly any stew or soup.  

This humble ingredient packs powerhouse flavor and can take a recipe from average to memorable with one simple addition. Although many people keep fresh onions on hand, don’t discount the power of frozen onion to rapidly elevate a recipe!

Should You Freeze Onions?

Is it worth it?

You may not think that freezing onions would be a big timesaver, but in fact, this trick can bring slow-cooked flavor to a quick weeknight meal. Not only that, but having frozen onions on hand reduces the interaction and handling with this tear-jerking vegetable, a real bonus for those who are particularly sensitive. 

Another benefit to freezing is that you can pre-cook the onions as desired, making them easier to add directly to a recipe. Try caramelizing them--talented home chefs swear by this shortcut.

While onions keep relatively well when fresh (up to a month), they last even longer in the freezer (up to six months), so freezing is also a way to take advantage of the harvest’s bounty if you have access to a farmer’s market or garden.

Flavor/Texture Changes?

As water freezes, it expands, rupturing the delicate cells of the onion. This causes the vegetable to lose its crispness. It will still present the unique taste of onion, but it will lack the kick that a fresh onion bestows upon salads and salsas.

Instead, try it in casseroles, soups, sautées, or skillets, where the loss of texture will not be noticeable. In any of these dishes, you will still experience the full richness of the onion’s flavor.  

How to Freeze Onions

There are several different ways to prepare onions before freezing them. You might choose to puree them, chop them finely or coarsely, or even freeze them whole.  

Frozen onion puree is ideal if you often use onions in sauces and gravies. Many people choose to freeze the puree in ice cube trays so that it is portioned conveniently. This way, you can toss a cube directly into the soup or gravy pot without the need to thaw it first! Once frozen, transfer the onion cubes to a well-sealed bag labeled with the date.

If you choose to freeze the onions in larger pieces, they will preserve their flavor better and remain incredibly versatile. Chop them to the desired size, then spread them on a baking sheet to freeze. Once they have hardened, scoop them into a well-labeled bag to save space. Alternatively, load each freezer bag with onions and then flatten the bags, removing as much air as possible. Stack them flat to freeze.  

The same technique applies to freezing whole onions, except that they benefit from being blanched before freezing. Blanching them briefly will improve the nutrition and flavor properties throughout the lifespan of the frozen vegetable, halting enzyme activity and reducing its microbial load.

Blanching is optional; you may freeze any fresh, clean, well-peeled onion without blanching, but you can expect a slightly longer frozen shelf life if you opt to include the blanching step. For best results, The National Center for Home Food Preservation recommends blanching for 3-7 minutes, or until the center of the onion has fully heated.  

For maximum injection of flavor, you might choose to caramelize your onions before freezing them. Caramelized onions dial up the sweetness as well as the roasted, toasted character of any dish.  Tossing in a handful of frozen caramelized onions is a way to quickly punch up the flavor of any recipe! 

When freezing onions, it is very important to place them in a container or bag that seals well. Not only does this protect the onions from oxidation and freezer burn, but it also prevents their odor from permeating the rest of your freezer. Avoid sandwich bags (which tear easily and seal poorly). Instead, spring for freezer bags or small tupperware containers.

How to Thaw Onions

It is rarely necessary to thaw pureed or diced onions before use. Because they are frequently used in cooking applications, you can rely on the heat of the sauce or the sautee pan to defrost them. Even in casseroles and baked dishes, you may add frozen onions and expect them to quickly thaw and cook alongside the other ingredients.  

However, if you need to defrost the onions, you will find that they thaw swiftly once you remove them from the freezer. Feel free to thaw them at room temperature for several hours if you plan to use them for dinner. Otherwise, an overnight stay in the fridge will defrost even a whole onion completely.  

If it is necessary to very rapidly defrost your onions, you may do so in the microwave; simply use a defrost setting or low-power setting for several minutes (depending on the size and quantity of onion pieces). Alternatively, stop the microwave every thirty seconds and turn or check the onion to confirm that defrosting is proceeding without cooking or drying parts of the onion.  

Uses for Frozen Onions

Pureed onions are an easy way to flavor soup, gravy, and stew. The small quantity which freezes in an ice cube will thaw immediately when tossed directly into a hot liquid, adding a lot of flavor very quickly. 

Try sautéing frozen diced onions with meat or including them in a savory pot pie. 

Larger sizes of onion (coarsely chopped or whole) make a great addition to casseroles, skillets, and other cooking methods. 

Avoid using any frozen onion as a substitute for fresh onion! Because an onion loses its crunch when frozen, a thawed onion would make a very disappointing salad addition or hamburger topping.

Frequently Asked Questions

Can I freeze red onions? 

You may freeze any type of onion if you follow the recommendations above. Red onions are typically used for fresh recipes, such as salads and taco topping; for such purposes, you might prefer to use fresh red onion. Yellow and white onions are better choices to use in cooked dishes.

Yellow onions are spicier and become more mellow with age and with longer cooking time; they are a popular option for casseroles and baked dishes. White onions are sweeter with less bite, and they are a favorite in sauces and gravies. All types of onion freeze equally well, so choose the type that you enjoy in your recipes.


Whether whole, pureed, chopped, or caramelized, onions quickly bring depth, flavor, and character to any recipe. A stash in the freezer is an efficient shortcut that takes your dish to the next level! 

If you have any questions or comments, don't hesitate to leave a note below. 




About the author

Caitlin is a Ph.D student and chocolate researcher at Colorado State University. Her research in the Food Science program focuses on chocolate fermentation (that’s right, it’s a fermented food!) and small-batch post-harvest processing techniques. When she is not acting in her capacity as resident chocolate guru, she researches other fermented foods and beverages like beer, sausage, and natto. Caitlin was drawn to fermented foods while living in rural Spain for six years, where she was exposed to traditional, time-honored practices of food preservation. At home, she practices Bollywood dance for fun and is followed everywhere by two small pet rabbits.

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