How Strong Does an Onion Taste? Depends on How You Cut It.

How—and how much—you cut an onion directly impacts its flavor.

Published July 7, 2022.

Sniff an intact onion, and you won’t smell anything. But slice that same onion, and it comes to life, unleashing a ripe, complex pungency that plays an integral role in just about every cuisine around the world.

That transformative nature, and tremendous range of flavor and aroma, is what makes onions so invaluable. And as cooks, we have the power to control their flavor—starting with the knife work. Depending on how—and how much—you cut them, onions can range from the raw bite in a salad or sandwich to the imperceptible but deeply aromatic depth in countless sautes, stir-fries, curries, and braises.

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How Onion Flavor Works

At the root of onion flavor are enzymes called onion alliinase and LF synthase, which are released the moment the vegetable’s cells are damaged and jump-start a pivotal chemical reaction. The enzymes act on a sulfur-containing molecule called isoalliin, converting it to harsh-tasting molecules called thiosulfinates. These thiosulfinates immediately start to change into a variety of other, often more mellow-tasting compounds, all of which in tandem are responsible for onion flavor.

More Cutting = Stronger Flavor

Manipulating onion flavor is all about controlling the creation and subsequent evolution of isoalliin. The more you break down onion cells by chopping, the more isoalliin is produced. Minced onion tastes stronger than chopped onion, which tastes stronger than sliced. 

Minced onion (left) tastes stronger than chopped onion because the former's cells are more broken down and have released more sulfur-rich isoalliin.

With the Grain = Milder Flavor; Against the Grain = Stronger Flavor

Even the way in which you cut the onion affects its pungency. Slicing pole to pole (with the grain) ruptures fewer cells than slicing parallel to the equator (against the grain), and thus produces fewer thiosulfinates.

Onion Flavor at Work

Want to get a sense for how impactful the cutting method can be? Cook your way through these recipes. 

Best French Onion Soup

If you're taking the time to make this soup, it better be perfect. Luckily, we discovered the secret for coaxing deep flavors out of your onions for the perfect soup.
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Sweet and Spicy Pickled Onions

These pickled onions are very loosely based on Mexican curtido, a relish of pickled vegetables.
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Classic Guacamole

A perfectly seasoned dip isn’t just stirred together. You have to cut and paste.
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Quick Tomato Sauce

Is it possible to transform canned tomatoes into a bright, fresh-tasting sauce?
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Palak Dal (Spinach Dal with Cumin and Mustard Seeds)

This Indian staple is quick, easy, nourishing, inexpensive, and—most important—incredibly flavorful.
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Rigatoni with Beef and Onion Ragu

We knew that the meat in this Neapolitan gravy would add big savory flavor. What we learned in the making was that the other key player—the onions—would, too.
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