Onion Powder: What It Is, How It Tastes, and How Much Replaces an Onion

How much onion powder equals one onion? Two university extension guides answer 1 teaspoon and 1 tablespoon, and they aren’t even talking about the same size of onion. Onion powder is just onion that’s been dried and ground fine. It gives you onion flavor without the moisture, texture or chopping of a fresh onion, so it shows up in dry rubs, seasoning blends, dips and dressings. And the compound that makes you cry when you chop an onion turns out not to be the one that makes it taste like onion.¹

At a glance

What onion powder is

USDA’s food composition data list onion powder as a spice made from Allium cepa, the common onion. Kew puts the onion in the Amaryllidaceae and describes its native range as “a cultigen from Central Asia.” In other words, it’s known from cultivation, not as a wild plant.⁴

Onions grown for drying are bred for the job. Oregon State University’s guide to onions for dehydration names soluble solids and pungency as the key economic factors, and notes that varieties developed for dehydration can reach 23% soluble solids or more. White types are the most common, since they make processing easier; yellow types are only used for special purposes. Many are hybrids developed and supplied by the dehydrating companies themselves. In the United States, OSU mentions Oregon’s Hermiston-Boardman area and California’s San Joaquin and Imperial valleys as growing areas.²

We didn’t find a statistical source for onion powder production by country. The popular claim that the US is the biggest producer and India second couldn’t be traced.

Flavor and the chemistry behind it

Onion powder tastes sweeter, rounder and less sharp than raw onion, with a slightly toasted note. It has neither the crisp bite of raw onion nor the deep caramel flavor of onions browned slowly in fat.

Fresh onion’s sulfur chemistry starts with the enzyme alliinase acting on a sulfur-containing precursor. For a long time, people assumed alliinase alone made the compound that makes your eyes water. In 2002 a team publishing in Nature showed otherwise. The tear-inducing “lachrymatory factor” is made by a separate enzyme they named lachrymatory-factor synthase, and the compound only formed when alliinase, the precursor and the new enzyme were all present. Fresh onion’s flavor, they wrote, comes from thiosulfinates, a different group of compounds.¹ So the sulfur compound that makes you cry isn’t the same as the ones that make onion taste like onion.

We didn’t find a published study on how drying and grinding change these compounds in onion powder, and we won’t guess. Garlic powder’s dormant enzyme is well documented (see garlic powder), but none of the sources we could open covers how onion powder’s enzymes behave once it’s rehydrated.

How much powder replaces an onion

Two university extension guides give different equivalents, and they aren’t measuring the same onion:

NMSU’s figure works out to three times as much powder, for a medium onion instead of a small one. Neither source defines those sizes, so their tables can’t settle the gap. Both are round-number kitchen rules, not flavor measurements. NDSU also lists 1 1/3 teaspoons of onion salt, or 1 to 2 tablespoons of minced dried onion, for a small onion.⁵ Start with the lower figure, 1 teaspoon per small onion, then taste and add more.

For other swaps, see onion powder substitutes, and for the side-by-side, onion powder vs. onion.

How onion powder is used

Onion powder goes where chopped onion would get in the way or add too much moisture: dry rubs for grilled and smoked meat, seasoning blends, breading and seasoned flour, dips, salad dressings, soups and gravies. It’s a regular in blends like taco seasoning, cajun seasoning, creole seasoning, adobo seasoning, poultry seasoning and seasoned salt, and it’s a natural partner for garlic powder, paprika and black pepper. For onion-forward cooking, see French onion soup spices.

Technique

• Let it sit before tasting. In dips and dressings, let the mix rest a few minutes before you adjust the seasoning.
• Keep it out of a hot, dry pan. Ground spices don’t do well under intense heat and can turn bitter. Add onion powder with liquid or once the fat has some other ingredients in it.
• Don’t double up on salt. Onion salt is a different product; see onion salt vs. onion powder.

Buying and storage

Good onion powder flows freely, is pale cream to off-white, and smells clearly of onion. Clumps mean it’s absorbed moisture. We didn’t find a grading standard for dried onion or a shelf-life figure from a regulator or standards body. Store it airtight, away from heat and humidity, and replace it when the smell gets faint.

Nutrition

USDA data for onion powder, per 100 g, show 341 kcal, 15.2 g fiber, 985 mg potassium, 384 mg calcium, 113 mg magnesium, 73 mg sodium and 23.4 mg vitamin C.³ A teaspoon weighs 2.4 g and a tablespoon 6.9 g,³ so at cooking amounts the numbers are small:

Calculated from USDA’s per-100 g values and portion weights; Daily Values from the FDA.³⁷ Plain onion powder adds almost no sodium. Onion salt, as the name says, adds salt. Onion powder isn’t a meaningful source of any nutrient at cooking amounts, and nothing we reviewed shows it treats or prevents any condition.

History

Onions have a long record as both food and folk medicine. Pliny the Elder recommended onion for the eyes, either by having the patient smell it until tears came or by rubbing the eyes with its juice, and fresh onion in vinegar, or dried onion with wine and honey, for dog bites. A note in the Bostock and Riley translation calls those supposed healing powers quite erroneous.⁸

Other popular history (onions in use by 5000 BC, onions in pharaohs’ tombs as symbols of eternal life, Roman soldiers carrying onions to Britain, and Egypt as the first place to grind dried onion) couldn’t be traced to a source we could open, so we’ve left it out.

Substitutes and comparisons

• Onion powder substitutes
• Onion powder vs. onion
• Onion salt vs. onion powder
• Onion salt and onion salt substitutes
• Garlic powder
• Chives