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 when you save the other half for later. 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 myceramicknives.com 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 that remained minimal. “[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 in under 10 minutes.
You can even 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 when cutting open an avocado—and it’s actually the healthiest part of the avocado too. “Most people will try and scoop under it, thereby removing more of the edible portion of the avocado and also exposing more or 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.
When it comes to shopping for your perfect plastic or ceramic 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 today.com, swears by her Kyocera ceramic knife, which currently costs about $35 on Amazon. “It’s the one kitchen utensil 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 ceramic knives shouldn’t be used to pry or twist things open or to cut through hard substances like bone or frozen foods because ceramic knife blades are much thinner than metal ones.
“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 26 brilliant storage tricks for foods.