How to Prevent Cut Apples From Browning, According to Food Scientists

Whether you're packing a snack, arranging a grazing board, or baking pies, there are plenty of reasons to stock up on apples. The only catch? Apples are notoriously difficult to store once cut, as they quickly turn brown. Unfortunately, it's not possible to completely stop this browning—but it can be delayed. Learn the different ways to slow down browning in freshly cut apples, including the best overall method, according to experts.

Why Cut Apples Turn Brown

"Apple cells contain an enzyme, polyphenol oxidase (PPO), that's only active once the apple's flesh is exposed to oxygen," explains Rosemary Trout, program director and assistant clinical professor of culinary arts and food science at Drexel University. This can happen when the apple is sliced, peeled, or bruised, she adds. The reaction increases the production of melanin, a pigment that creates the brown color in apple flesh.

Are Brown Apples Safe to Eat?

Though unsightly, apple slices that have browned are still safe to eat, says Bryan Quoc Le, PhD, food scientist, food consultant, and author of 150 Food Science Questions Answered. That's because the enzymatic reaction that causes browning doesn't affect the safety (i.e., level of harmful microorganisms) in the apple.

However, cut apples that have been stored in water can become mushy over time. This is worth keeping in mind, especially if you dislike certain textures.

The Best Way to Prevent Cut Apples From Browning

Dipping cut apples in salt water is the best way to delay browning, says Kimberly Knight, chef-instructor at the Institute of Culinary Education.

It works because salt has a low oxygen solubility, which further prevents PPO from accessing oxygen, says Trout. Plus, the salt content "causes the enzyme to undergo a process known as denaturation, resulting in deactivation," shares Le.

To use salt water, follow these steps from Trout:

1. Combine 8 ounces of water with ½ teaspoon salt.
2. Dip the cut apples in the salt water for 1 to 3 minutes.
3. Remove the apples and store them in an airtight container in the refrigerator.

How long it lasts: Salt water can delay browning for about 12 hours. The cut apples won't taste like salt, but you can quickly rinse them off if you're concerned about a salty flavor.

5 Other Ways to Prevent Cut Apples From Browning

If you don't want to use salt water, there are other ways to slow down the browning reaction in cut apples.

Submerging in Plain Water

Here's how to use plain water, according to Knight:

1. Add the cut apples to a resealable bag or a container with an air-tight lid.
2. Fill the bag or container with room-temperature tap water.
3. Seal tightly and store in the refrigerator.

"Apples in plain water will retain their crunch and taste for up to six hours before they'll start to brown," says Knight.

Sprinkling With Lemon Juice

Another method is to apply lemon juice directly on the apples. The acidity of the lemon juice will lower the pH of the apple, which decreases PPO activity, says Trout.

"Additionally, lemon juice contains a high concentration of vitamin C, or ascorbic acid, which readily reacts with oxygen and removes [it] from the surface of the apple," explains Le. "This helps prevent the production of brown compounds from the enzymes, he adds.

Follow these steps to use lemon juice to delay cut apples from browning:

1. Slice a fresh lemon in half.
2. Squeeze the lemon over the cut apples, making sure the juice comes into contact
   with the flesh.
3. Let the apples rest for 5 minutes, then rinse off the juice in a colander.
4. Store the apples in the refrigerator in a sealed container.

This method can delay browning for about seven hours, according to Knight.

Submerging in Lemon Water

You can also keep cut apples in a mixture of water and lemon juice. As mentioned above, lemon juice will reduce the activity of PPO and decrease oxygen exposure.

To use lemon water, follow these steps:

1. Add 1 tablespoon lemon juice to 8 to 10 ounces of water.
2. Soak the cut apples in the lemon water for 3 to 5 minutes.
3. Drain and rinse the apples.

Typically, this technique will delay browning for two to three hours.

Submerging in Sugar Water

Another technique is to soak the cut apples in sugar water. Sugar, like salt, prevents PPO from accessing oxygen, according to Trout.

Here's how to use this method:

1. Add 1 tablespoon of sugar to 8 ounces of water.
2. Soak the cut apples in the sugar water for 3 to 5 minutes.
3. Drain and rinse the apples.

You can also use honey instead of sugar, but sugar is much more cost-effective.

Blanching

If you plan to use cut apples for baking, try blanching them first. The heat will deactivate the PPO in the apples, helping slow down browning.

1. Bring a pot of water to a boil.
2. Add cut apples to the water.
3. Cook the apples for 30 seconds.
4. Using a slotted spoon, remove the apples from the water.
5. Place the apples in a bowl of iced water, then drain.
   

Refrigerating Cut Apples

If you don't plan to eat the cut apples right away, store them in the refrigerator after using any of these methods. The low temperature inside the fridge will slow down the activity of PPO, further delaying browning. Be sure to place the apples in an airtight container first to reduce oxygen exposure.

Le adds that refrigeration slows down the growth of harmful bacteria on the apple's flesh and reduces the chances of mold.

For best results, he recommends eating the apples within three to five days.

When to Toss Cut Apples

If your cut apples have mold or a slimy texture, it means they've gone bad, says Le. You should also toss the apples if they have an odor that's earthy, musty, or alcoholic.