Why an Ice Bath Is the Key to Fresher, Greener Vegetables

An ice bath is one of the unsung heroes of my kitchen, but I haven’t always given it the credit it deserves. When I’m cooking I almost always keep a big bowl of ice water nearby because it buys me time and maintains the quality of my ingredients. At its simplest an ice water bath can rapidly chill ingredients. And sure, a refrigerator can chill things too—but if you tried to chill a custard for ice cream in the fridge, it would take hours or even a full day, as opposed to minutes with an ice bath. When you’re working with delicate ingredients like a soft-boiled egg or freshly blanched green beans, the cooling power of a refrigerator simply can’t work fast enough.

I know some people view preparing an ice bath as a mundane, even unnecessary step that only delays the race to the recipe finish line. But hear me out: An ice water bath is more than just “a pretend pond on the kitchen table,” as a friend once called it. It’s an insurance policy for keeping ingredients looking and tasting their best. A bowl of ice water will make your vegetables shine, stay crisp, or even beautifully twist and curl—but it can also transform flavors and be the critical variable that makes the difference between a merely good and an excellent dish.

Let’s take a closer look and see why an ice bath should be part of your essential kitchen toolkit.

When I’m putting a salad together, I set a big bowl of ice water on my kitchen island next to my cutting board. I’ll dunk the carrots, onions, lettuce, radishes, or whatever fresh produce I’m cutting straight into the water while prepping. Why? The cold bath keeps the cut vegetables from losing water, preventing them from turning limp. Once I’m done getting all the mise en place prepped, I’ll discard the water and pat the vegetables dry before tossing them with the dressing, ensuring beautiful, crunchy vegetables that won’t be soft when I eat them.

But that’s only one of an ice bath’s many tricks. Have you ever noticed those pretty little scallion curls that garnish fried rice or sushi at restaurants? It’s an elegant but simple technique that’s easy to recreate at home.

Here’s how: Take a handful of scallions and cut them into one or two-inch segments. Then, slice each segment lengthwise into thin sections and place them in a bowl of ice-cold water; within five minutes, they’ll start to curl.

These magnificent scallion curls appear because the cut side of the vegetable has been exposed—similar to how those salad vegetables start to absorb the water in which they’re immersed, leading to an increase in the intracellular volume of the vegetable. The outer surface of the vegetable cannot absorb water, however, and this uneven absorption rate on either side of the scallion causes it to stretch and form curls. The geometry of the cut defines how the cut vegetable changes its shape. If the scallions were thinly sliced into rings and immersed in water, they’d still absorb water, but the expansion would occur radially so that the change wouldn’t be visible.

Raw alliums like onions, leeks, and shallots are notorious for the pungency and bitterness that arises when they’re freshly cut. Inside the cells of an allium are sulfuric compounds called S-alk(en)yl-L-cysteine sulfoxides (ASCOs) and an enzyme called alliinase. These compounds are separated from one another by special intracellular compartments; when an onion is cut, the cells break, and those compartments fall apart. The ASCOs and alliinase instantaneously come together to kick off a cascade of chemical reactions that produce those characteristic pungent, astringent, and bitter-tasting flavors we immediately recognize.

To reduce the intensity of these flavors, recipes sometimes instruct the reader to soak the cut alliums in a bath of ice-cold water. The chilled water bath does two things: First, it dilutes and washes away those harsh flavor molecules. Second, it stops the enzyme alliinase from doing its job. Alliinase works best at warmer temperatures, and the cold temperature of the water bath ceases the enzyme’s ability to work, so you must quickly transfer the chopped alliums to the water bath to stop the enzyme. If you’re curious, taste the water in which you soaked the alliums—you’ll pick up a bitter aftertaste.

Water possesses an amazing ability to absorb a large amount of heat, making it an extremely useful ally in the kitchen. Take two freshly soft-boiled eggs you’ve just pulled from the boiling water in your saucepan. Leave one somewhere safe on the kitchen counter and immerse the other in an ice-cold water bath for 30 minutes. The one from the ice-water bath will have a softer, runnier yolk than the one left on the counter to cool. An ice water bath will slow down and stop the cooking process rapidly because water absorbs a large amount of energy in the form of heat. A refrigerator, on the other hand, cools things much more slowly than water because air has a lower heat capacity (a tiny fraction when compared to the heat capacity of water) and is not as dense.

When I’m blanching vegetables, I always keep a bowl of ice water near me. As the vegetables stay submerged in the boiling water, their cell walls soften, making them tender and easier to eat. The colors of vegetables also begin to change. After they’ve been blanched, green vegetables like asparagus, broccoli, and green beans that contain the pigment chlorophyll start to turn bright green, because the cell walls fall apart and increase the visibility of chlorophyll. If blanched for too long in the boiling water, the chlorophyll undergoes chemical changes, turning it a dull, grayish-green. Even if the beans are removed from the boiling water when they’re still bright green, there’s still a good chance they will continue cooking at room temperature because they’re still hot—and eventually, they’ll turn limp and a drab shade of green.

To keep those green beans, broccoli, asparagus, or leafy greens really green, submerge them in an ice water bath the moment you pull them out of the boiling water. This will keep them vibrantly green with a pleasing snap.

Rather than looking at an ice bath as a tedious extra step, think of it as the easiest and most economical way to produce bright, crisp vegetables, perfectly cooked eggs, and restaurant-quality garnishes. Your recipes will turn out all the better for it.

Originally Appeared on Epicurious

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