Picture this: You’re toting an orchard’s-worth of fresh apples home from your local farmers market, dreaming about the many ways you’ll put the haul to use (apple pie! applesauce! caramel apple cheesecake!). Upon your arrival, you can hardly wait for a taste, so you slice into one of those gorgeous apples and behold its juicy, glistening interior, all white and creamy and crisp. You turn around to grab the peanut butter, but when you look back to the cutting board—no, that can’t be! The flesh of the apple has already started turning brown.
No matter how fresh the fruit is, a sliced apple is likely to start browning in a grand total of two minutes. Why does your favorite fall fruit seem to deteriorate so quickly? And how can you stop apples from browning forevermore? The truth is, you can’t. But there are some things you can do to delay the process.
Home cooks have come up with plenty of creative ways to keep sliced apples from turning brown, such as rubbing slices with lemon juice or soaking apples in honey water or lemon-lime soda. But Which of these methods actually work? More on that below, but first: Why is your perfect apple changing the color of its flesh in the first place?
Why do apples brown when sliced?
According to Tenley Fitzgerald, vice president of marketing at Yes! Apples, a network of New York–based apple farms, the unsightly hue is the result of a process called enzymatic browning. For more on what that means, I spoke to Christopher Watkins, a professor at Cornell’s School of Integrative Plant Science Horticulture Section, whose research focuses on apple storage life and quality. Watkins explains that visual browning is the by-product of an interaction between the apple’s naturally occurring phenolic compounds and an enzyme called polyphenol oxidase (PPO). “Normally the phenols and PPO are [stored] in separate places in the cell,” Watkins explains. But when you slice into an apple, you damage the membranes, allowing these enzymes to come into contact. PPO facilitates the reaction between the phenols and oxygen, causing the apple to produce brown-colored melanins. (Yes, the same melanin that brings color to human skin.)
But why do some types of apples brown faster than others? Different varieties of the fruit contain varying amounts of the above compounds. “You can have an apple variety with high phenolics but low enzyme activity, and the reverse,” says Watkins. Antioxidants also play a role here: They slow the chemical reaction, so apples with high antioxidant levels are slower to brown.
McIntosh, Golden Delicious, and Fuji apples are relatively quick to brown; Honeycrisp and Snapdragon apples brown at a moderate rate; and Pink Lady, Empire, and Cortland apples are slow to brown. “Browning resistance can be passed down genetically through apple breeding programs,” says Watkins. Some of the most popular apple varieties, like white-fleshed Pink Lady apples, are a direct result of such crossbreeding. Only one variety of the fruit—Arctic apples—has been genetically engineered to not brown. All in all, a lesson in why it’s important to choose your apples wisely.
Environmental factors (like the ambient temperature and oxygen level) also play a role in how quickly a sliced apple will turn brown. The more oxygen exposure, the faster an apple slice will brown. The lower the temperature, the slower the reaction, according to Watkins.
The 6 best ways to prevent apples from browning:
If you’re baking apples into a pie or a crisp, the browning doesn’t matter so much—after all, they’ll just brown more in the oven. But if it’s picture-perfect slices you’re after—say, for a charcuterie board, an apple tart, or the kids’ lunch boxes—try one of the below methods to slow the oxidation process.
Note that these tricks to keep apple slices white and crisp work only in the short-term: All sliced apples will brown over time (that is, unless you get the genetically engineered kind). It’s the cycle of life. Embrace it. Browned apple slices might not be the prettiest, but they’re still perfectly fine to eat. “Browning does not change the flavor of the apple or suggest deterioration,” says Fitzgerald.
First things first: Choose the right apple. Watkins advises selecting a low-browning susceptible apple, like Pink Lady, Empire, Cortland, RubyFrost, Ambrosia, Ginger Gold, or EverCrisp.
The easiest step you can take to avoid browning is to reduce the sliced apple’s exposure to air. There are a few ways to do this (one popular technique is to hold the apple slices together with a rubber band), but our favorite method requires no dexterity or special equipment. It’s simple: Submerge your apple slices in plain water. “Water has two effects—it washes the damaged cells, but more importantly reduces the oxygen levels around the slices,” says Watkins.
Fill a medium-size bowl with cold water, then place your apple slices in the bowl. Since the slices will float to the top of the water, place a clean paper towel on the water’s surface. Once the paper towel is wet, it will push the apples under the surface.
Since salt is a preservative, adding a pinch of kosher or table salt to the soaking water can keep the apple slices looking fresh. Dissolve ⅛ teaspoon kosher salt in 1 cup water. Add the apple slices, let them soak for 1–3 minutes (be careful not to let the apple slices soak too long, or they’ll absorb the salty flavor), then drain them in a colander. Rinse the slices with fresh water.
“There is a compound in honey that stops the enzyme responsible for oxidation,” writes Epi contributor Sheela Prakash on why honey can be an effective antidote to browning. Whisk 2 tablespoons honey into 1 cup water and soak your apple slices in the mixture for 1–3 minutes. Drain and give them a quick rinse with fresh water (or skip the rinse if you don’t mind the honey flavor).
Remember what we said before about apples with high antioxidant levels? (Hint: They’re slower to brown.) Even if you’re using apples with low antioxidant levels, you can add another ingredient that’s high in antioxidants, such as citrus juice, to discourage browning.
Perhaps the most common method to keep apples from browning is to rub them with lemon juice, a source of ascorbic acid (or vitamin C). “Commercially, apple slices are treated with ascorbic acid [to prevent browning],” Watkins says. Any type of citrus juice—lemon, lime, or orange juice—will work here; pineapple juice will do the trick too. These fruit juices contain citric acid, which slows the chemical reaction and prevents browning. (You can also sprinkle the fruit with powdered citric acid, but it may leave a strong sour flavor.)
If submerging the apples, add 2 tablespoons lemon (or other citrus) juice to the water to further discourage browning. Let them soak in the lemon water for 1–3 minutes, drain, and rinse. Or simply squeeze the juice of a lemon, lime, or orange directly onto the surface of the cut apples. Again, the citrus juice may impart a bit of flavor to the apples.
The best way to keep apples from browning is to reduce or eliminate the apple’s exposure to air. After you’ve chosen one of the above methods and treated your apples, store the slices in an airtight container or a resealable plastic bag with the air pressed out. This can mitigate browning, but be warned, advises Watkins: deny the apples oxygen for too long, and it can result in fermentation.
Storing cut apples in the refrigerator will also help. If you leave a sliced apple at room temperature, it’ll brown at an exponentially faster rate than if stored in the fridge. That’s because the lower temperature slows the reactions between the enzymes, prolonging the browning process. Keep the cut apples in the fridge for up to 6 hours.
