Raw onions are a polarizing ingredient. I can understand why. The biting flavor can overwhelm any dish and linger in my mouth for hours. That said, sometimes a hit of spiciness and crunch is just what I need in a cucumber salad or veggie sandwich. And now that we are deep into summer, I find myself adding thinly sliced onions to pasta salads, easy wraps, and grilled burgers.
If you’re not a fan and opt to skip raw onions for fear of never-ending dragon breath, try this simple tip for taming its punch and mellowing its flavor.
The Trick for Taking the Bite Out of Onions
In culinary school, I was taught to soak onions and other alliums like shallots in an ice bath—a bowl filled with water and ice—for 10 to 20 minutes to tame the bite and mellow the flavor while crisping up the texture. After soaking, the onions are drained.
Back then, I never questioned advice from my chef instructor (Yes, Chef!) and I never thought about why and how this tip worked. Like most things I learned in cooking school, it became part of my everyday practice in the kitchen.
At a recent BBQ I brought a summer panzanella and a former raw onion hater in attendance asked me how I was able to use so many of them without overwhelming everything else.
I happily explained the simple trick I learned years ago, but was not prepared for what came next; “But how?” Great question. While I wanted to reply, “Because Chef said so,” that didn’t feel appropriate for someone pushing 40. Not being able to answer the question stung, so I set out to find out.
Why Soaking Onions in Cold Water Works
Quick research revealed that onions and all alliums are full of sulfur—they grow in the ground and absorb sulfur from the soil. These sulfur compounds are responsible for the tears we experience when cutting onions, as well as their assertive flavor.
When onions are sliced, these sulfuric enzymes are released and hang out on the surface of the onion. When you soak them in cold water, two things happen. The water rinses the enzymes off and the cold temperature makes them less reactive. This is why some people suggest freezing an onion for a few minutes before slicing it to cut back on tears.
Other Methods That Work
An ice bath is best if you want crunchy onions, but if you don’t mind a softer texture, vinegar or lemon juice works. If I’m making a pasta salad, I usually soak the onions in the vinaigrette without the extra step of making an ice bath and draining them. The folks at Milk Street suggest salting the onions, which breaks down the fibrous texture and mellows out the flavor.