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Home » Produce guides » Sweet onions

Published: Apr 15, 2021 · Modified: Oct 25, 2023 by Veronica T

Sweet onions

sweet onions (vidalia, walla walla), in season

Sweet onions have a mild, less pungent flavor than regular yellow, white, or red onions, due to their lower sulfur contents. That also makes them taste sweeter, even though they don't have more sugar content.

Jump to:
  • Varieties
  • What makes these onions sweet?
  • Selection & storage
  • Recipes

Varieties

Vidalia, Walla Walla, and Maui are the most widely available sweet onions and are all quite similar in flavor. Their seasons differ just slightly.

  • Maui: Peak: April - August, but can be found year round
  • Vidalia: April - August
  • Walla Walla: June - September
  • Texas Sweet: April - June

What makes these onions sweet?

Sweet onions aren't actually sweeter - it has nothing to do with the sugar content. It's actually due to other factors that reduce the the sharp flavor, making the flavor milder.

Major influences on sweet onion's mild flavor:

  • Genetics & pyruvic acid: sweet onion varieties genetically have about 50% less pyruvic acid than regular onions, which gives them less of a bite. Pyruvic acid is the biggets contributors to onion's pungent flavor. Regular onions have a 10-14% concentration of pyruvic acid, whereas sweet onions have less than 5%.
  • Soil & sulfur: Vidalia onions in Georgia are grown in low-sulfur soil and Walla Walla and Maui onions are grown in low-sulfur volcanic soil. Sulfur adds to that 'bite' so it is intentionally kept as low as possible, including careful use of low-sulfur fertilizer.
  • Water: sweet onions also have higher water content, which essentially 'waters down' the strong flavor.

As I mentioned, sweet onions don't actually have a higher amount of sugar than other types of onions, as shown in this chart.

Type of onionSugar (per 100g serving)Sulfur content
Shallots7.7glow
Pearl onions4.7glow
Sweet onions4.5glow
Red onions4.3ghigh
White onions4.3ghigh
Yellow onions4.3ghigh
Green onions2.3glow
Onion sugar and sulfur content

For comparison, a 100g serving of lemons have 2.5g of sugar and 10.4g for apples.

Other mild onions, like shallots and pearl onions have less sulfur for similar reasons.

Sources

  • Sulfur compounds identification and quantification
  • Onion Flavor and Odor, Enzymatic Development of Pyruvic Acid in Onion as a Measure of Pungency
  • Oregon State horticulture department

Selection & storage

Choose onions that have no bruising or soft spots and have a closed 'neck' at the top.

The higher water content in sweet onions makes them spoil faster than regular onions. They should be handled with care since they are more fragile.

Storage instructions

  • On the counter: they will last for about a week
  • In a cool, dry place: they can last for about a month. Keep them away from potatoes and try to not let them touch to prevent bruising and spoiling.
  • In the fridge: They can last more than a month in the fridge. Store loose or in paper bags. Avoid plastic as that can cause the onions to mold.

Recipes

The milder flavor from sweet onions makes them ideal for recipes with a lot of onions. It keeps the onion flavor from overpowering everything else. This is why they are excellent for onion rings, soups, and dips.

The sweet onion recipe collection has over 40 recipes for salads, sides, dips, and French onion riffs.

Sweet onion recipes for spring & summer
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Welcome, I'm Veronica, your resident food geek - experienced recipe developer and gardener. My goal is to help you enjoy eating at home by knowing what fruits & vegetables are currently in season and the best ways to use them. To do that, I've put together seasonal produce guides and recipes with practical advice.

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