Here’s Why You Shouldn’t Use a Metal Knife to Cut an Avocado

Who knew that a knife could change how much you enjoy avocados?

Most people slice open an avocado without giving it a second thought. But the type of knife you use can play a role in how quickly the avocado’s creamy green flesh turns brown.

Psst! Here’s what happens when you eat avocado every day.

Why do avocados turn brown?

Much like apples and eggplants, avocados contain an enzyme that causes the flesh to brown when it’s exposed to oxygen in the air. “Browning is a natural reaction that is going to occur and is impossible to stop,” says Nick Stellino, celebrity chef and TV show star of Storyteller in the Kitchen. “However, metal knives, specifically those containing the elements of copper and iron, will start the browning process a little sooner than those made from plastic or ceramic.”

Keep in mind that cutting an avocado with a ceramic or plastic knife won’t keep your avocado green for days, but it can salvage you a few more hours before the flesh begins to discolor. In fact, a blogger at conducted a not-so-scientific test to see if an avocado browned quicker using a metal knife or a ceramic knife. The half cut with the metal knife began showing some dark brown spots that merged together, while the half cut by the ceramic knife only showed some faint browning.

“[The amount of time it takes to brown] also depends on the ripeness of the avocado prior to when you cut into it,” says Stellino. “If an avocado is well beyond its ripeness, and is soft and mushy to the touch, the browning process will move at a more rapid pace.” On the other hand, if your avocado is rock hard, this is how you can ripen it quickly.

You can slow down the browning rate even more by paying attention to how you cut the avocado, too. Removing the pit is the biggest mistake Stellino sees people make. “Most people will try and scoop under it, thereby removing more of the edible portion of the avocado and also exposing more of the metal knife to the avocado,” he says. “This will increase the rate of browning, not to mention give you less of the avocado to work with.”

Instead, he recommends using your knife to chop into the pit from above. This allows you to latch onto the pit and pull it out without the metal ever touching the fleshy pulp. “And perhaps more important than the cutting technique when working with avocados is the sharpness of your knife,” says Stellino. “The sharper the knife, the cleaner your cut will be. This will keep more of the actual avocado intact, which can also slow down the browning process.” Here’s the single best way to keep your knives sharp.

How to choose a knife:

When it comes to shopping for the perfect knife, there really is no particular brand that is better than another. It’s all based on your personal preference. “For the average person who cooks at home, most brands found in stores and online will do just fine,” says Stellino. “People have to see what feels best in their hands and what works with what they are cooking.”

Lindsay Lowe, a writer for, swears by her Kyocera ceramic knife ($35). “It’s the one kitchen utensil that has truly transformed my cooking life,” she writes. “The ceramic blade slid right through the bread almost like it was butter. The same goes for cutting fruits, vegetables, fish and even cuts of boneless meat.” Just remember that because of their thin blades, ceramic knives shouldn’t be used to pry or twist things open or to cut through hard substances like bone or frozen foods.

“Regardless of what you do, avocados will brown no matter what so it’s best to eat them within a day or two of cutting into them,” says Stellino. “And for storage, seal the avocado in an air-tight bag and place in the refrigerator as soon as possible.”

Now that you know how to properly cut your avocado to make it last longer, check out these other brilliant storage tricks for foods.

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Originally Published on Reader's Digest