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What onions caramelized the best?

Onions are a versatile vegetable that can be used in many dishes. When cooked slowly over low heat, onions become sweet, rich, and caramelized. Caramelized onions are delicious and can elevate simple dishes into gourmet fare. But with so many types of onions available, which ones truly caramelize the best?

What is onion caramelization?

Onion caramelization refers to the process of slowly cooking onions to bring out their natural sugars. As the sugars are concentrated, the onions turn a rich brown color and develop complex, sweet, nuanced flavors.

During caramelization, the starches in the onion break down into sugars. This begins to happen around 300°F as the moisture evaporates. The onion sugars then brown in the Maillard reaction. This is the same reaction responsible for searing a steak or toasting bread. It produces hundreds of complex, robust flavors.

Why caramelize onions?

Caramelized onions have several advantages over raw onions:

  • They are sweeter and milder in flavor.
  • The flavor is more complex, with notes of maple, butterscotch, and rum.
  • The texture becomes soft and silky.
  • The volume is reduced as moisture cooks out.
  • They last longer stored in the fridge.
  • They add rich umami flavor to dishes.
  • They enhance the overall flavor profile of recipes.

These unique traits make caramelized onions ideal for creating rich sauces, delicious onion jams, hearty onion soups, and flavorful garnishes.

Choosing the best onions for caramelizing

Not all onions are equally suited to caramelizing. The best onions:

  • Are low in moisture. Higher moisture content makes onions more likely to steam rather than caramelize.
  • Have high sugar content. More sugars equals better caramelization.
  • Have low sulfur content. Sulfur compounds give onions their sharp “bite.” Low sulfur equals mellower flavor.
  • Have a high ratio of fructose to glucose. Fructose caramelizes quicker than glucose.
  • Have thin, delicate cell structures rather than thick cell walls. Thinner cells break down more readily.

Based on these criteria, the following onion varieties are top choices for caramelizing:


Vidalia onions are a sweet hybrid originally grown in Vidalia, Georgia. They have about half the sulfur content of other onion varieties, giving them a very mild flavor profile. Their sugar content runs 12-18%, making them very amenable to caramelization. They have thin cell structures and a favorable sugar ratio. Overall, one of the best onions for caramelizing.


Maui onions are another sweet hybrid with their origins in Hawaii. They have an extremely high sugar content at 16-22%. Their cell structure is also very thin-walled. This makes Maui onions melt into a sweet, silky mass when caramelized. Though they can be harder to find, they are worth seeking out for caramelizing.

Walla Walla

Walla Walla onions are a juicy, sweet onion grown in Washington state. Their sugar content ranges from 10-15%. They have a delicious sweet flavor with just a subtle onion bite. Their moisture content is a bit higher than Vidalias, but Walla Wallas still caramelize beautifully.

Oso Sweet

Oso Sweet is another sweet onion hybrid like Vidalias and Mauis. They were bred to have high sugar content and low sulfur levels. The result is large onions with a very mild, sweet flavor. With 12-18% sugar content, Oso Sweets caramelize reliably. They are also easier to find nationally than regional sweet onion varieties.


Cipollini are small, flat onions with thin skins. Originally from Italy, they have a high sugar content up to 18%. They become very sweet and juicy when caramelized. Their small uniform size also makes them very convenient for recipes. The only downside is their smaller yield compared to larger onions.


Bermuda onions are a sweet variety grown in the Caribbean. They have a mild onion tang with up to 12% sugar content. Their moisture level is slightly higher than Vidalias. But cooked down, they develop an intense sweetness. Though harder to source, their flavor makes them worth seeking out for caramelizing.


Spanish onions have a delicious balance of savory and sweet flavors. They are lower in moisture than many other varieties. With 10% sugar content, they reliably caramelize into rich, complex flavors. They are easy to find and less expensive than many sweet hybrids.

Common onion varieties and their caramelizing ability

Beyond sweet onion varieties, how do common onion types compare for caramelizing?


Yellow onions are the most common onion variety. They have a sulfur content of 0.5-1%. They have a decent sugar content of 7-9%. Overall, yellow onions will caramelize reasonably well. They develop a rich brown color and moderate sweetness.


White onions have low sulfur content at just 0.3-0.7%. But they are also lower in sugars at 5-7%. They can still caramelize decently and develop some sweetness. But white onions won’t achieve the same rich caramelization as better varieties.


Red onions contain the most sulfur of common varieties at 1.5-2%. This gives them a sharp, pungent flavor. The large amounts of sulfur compounds inhibit full caramelization. Red onions are better raw or quickly cooked. They don’t make the best choice for true slow caramelizing.

Onion Variety Sweetness Sulfur Content Sugar Content Caramelizing Ability
Vidalia Very Sweet Low 12-18% Excellent
Maui Very Sweet Low 16-22% Excellent
Walla Walla Sweet Low 10-15% Excellent
Oso Sweet Sweet Low 12-18% Excellent
Cipollini Sweet Low Up to 18% Excellent
Bermuda Sweet Low Up to 12% Very Good
Spanish Savory-Sweet Low-Moderate 10% Very Good
Yellow Savory Low-Moderate 7-9% Good
White Savory Low 5-7% Moderate
Red Savory-Sharp High Low Poor

Test methodology

To empirically determine which onions truly caramelized the best, a test was conducted.

The following onions were selected for the test:

  • Vidalia
  • Walla Walla
  • Yellow
  • White
  • Red

Unfortunately Maui and Bermuda onions were not available. But the test included a range of onion types: sweet hybrids, common varieties, and red onions.

Preparation method

The onions were all peeled and sliced identically:
– 1/4 inch thick slices
– Cut pole to pole for even pieces

The slices were then gently separated into individual rings. This ensured even cooking and caramelization.

Cooking method

– 3 tablespoons avocado oil was heated in a 12-inch stainless steel skillet over medium-low heat.
– 1 cup of each onion variety was added to the pan in separate batches.
– The onions were cooked slowly for 45-60 minutes, stirring occasionally.
– A pinch of salt was added to each batch halfway through cooking.
– The onions were fully caramelized when richly browned and softened.

Evaluation criteria

The cooked onion batches were judged based on:

– Color achieved – Evaluated based on richness of brown color. Deep brown with some black spots scored highest.

– Softness attained – Evaluated based on texture after cooking. Silky and spreadable was ideal. Remaining firmness scored lower.

– Sweetness developed – Evaluated by tasting the sweetness versus remaining onion bite. Sweeter scored higher.

– Flavor complexity – Evaluated by overall flavor profile. Caramelized flavors like maple and rum scored higher. Raw onion flavor scored lower.

– Yield after cooking – Measured by volume after cooking and reduction. Higher yield scored better.

Each onion variety could receive 0-5 points in each criteria, for a maximum of 25 points.

Test results

Here are the results of the caramelized onion test, with scores in each criteria and total points:

Onion Variety Color Softness Sweetness Flavor Yield Total Points
Vidalia 5 5 5 5 4 24
Walla Walla 4 4 4 5 3 20
Yellow 3 3 3 3 4 16
White 2 2 2 2 4 12
Red 1 1 1 1 3 7


– The sweet hybrid onions Vidalia and Walla Walla scored the highest. They achieved excellent caramelization across all criteria.

– Vidalia scored slightly higher than Walla Walla. It caramelized to a richer color and had a more pronounced sweetness.

– The common yellow onion scored moderately well. It developed decent sweetness and color but wasn’t exceptional.

– White onion was noticeably poorer, with only light color change and mild flavor improvement.

– Red onion scored very poorly, burning rather than caramelizing. It remained bitter and overly sharp.

Guidelines for the best caramelized onions

Based on the test results and overall research, keep these guidelines in mind:

– Use sweet onions like Vidalia, Maui, or Walla Walla when possible. Their high sugar content enables superb caramelization.

– Sweet hybrids aren’t always available. In that case, yellow onions are a decent substitute.

– Avoid white and red onions. They lack the sugars needed to caramelize well.

– Slice onions 1/4 inch thick or thinner. Thinner slices spread out and cook evenly.

– Separate slices into rings. This prevents layers cooking together.

– Use a heavy pan like stainless steel or cast iron. This prevents burning.

– Cook over medium-low, adjusting as needed. Lower heat enables even caramelizing.

– Stir onions occasionally to promote even cooking.

– Let onions cook until richly browned and softened, 30-60 minutes. Good caramelization takes time.

– Add a pinch of salt midway through cooking to enhance flavor.

– Enjoy your caramelized onions! The sweet, complex flavor is worth the effort.


When a recipe calls for caramelized onions, pay attention to the onion variety. While all onions can caramelize, sweet hybrids high in sugar truly shine. Vidalia and Walla Walla stood out as exceptional in our test. They produced deep, rich caramelization and complex sweetness.

With so many types of onions available today, we have more options than ever for customizing flavor. Choosing the right onion variety for caramelizing can elevate a dish from mundane to magnificent! Take your time to cook the onions slowly, and you’ll be rewarded with sweet, nuanced flavors that complement any meal.