The Onion Mistake That's Causing Your Tuna Poke Bowl To Suffer

Poke has been integral to Hawaiian cuisine and culture for centuries, but the ahi tuna poke bowl is a relative newcomer, arriving on the Hawaiian food scene in the 1970s. In its original form, poke had Maui onion sprinkled over the chopped raw fish, and with the influx of Asian immigrants to Hawaii, other ingredients, like soy sauce, sesame oil, and green onions were added. Maui onions are specific to Hawaii and have a sweetness and mellowness noticeably lacking in other onions. Maui onions aren't as readily available on the mainland, and red, yellow, or white onions are often substituted for the Hawaiian variety. 

When sliced or chopped, almost all onions release enzymes that create a sulfurous compound, which results in teary eyes and a strong smell and taste that overwhelm the fresh raw tuna in a poke bowl. Vidalia, Bermuda, and Walla Walla onions don't emit the fume-causing enzymes and can be used instead of Maui onions. But if you're only able to find regular onions, you can reduce their harsh bite with a few simple steps. First, before you cut any onion, make sure you're using a knife you sharpen often. When an onion is cut, its cells are crushed, which in turn creates the chemical reaction that releases the irritant sulfides. Thus, the sharper the knife, the less cells that are crushed. Avoid chopping the onion too finely, because again, the more you destroy the onion's cells, the more pronounced the onion's odor and taste.

As an onion grows, its roots draw up the sulfur from the soil. So one of the ways that you could reduce the sulfuric compound from forming is to leave the root intact. The direction that you cut the onion will also affect the release of the fumes. An onion's cell walls have a horizontal grain, and if you slice an onion in half cross-wise, you're cutting against the grain and thus ripping across more cells, which then kicks the chemical reaction with the onion's sulfides into high gear. Lemon's high acidity neutralizes onion smell, so while cutting an onion, rub the knife's blade repeatedly against a cut lemon. 

Another trick for diminishing an onion's sharp bite without sacrificing its flavor is to soak the sliced or chopped onion in a bowl of ice water for 15 minutes, change the water, and soak for an additional 15 minutes. The ice water removes the onion's odiferous enzyme and retains the onion's crunchy texture. You might also forgo the onion altogether by replacing it with shallots or green onions (scallions), two of the most popular types of onions, that some tuna poke bowl recipes add instead for their subtler flavor and less aggressive bite. Finally, whichever onion you use, go gentle, since you want the ahi tuna to be the showstopper of your poke bowl.