When an apple is cut (or bruised), oxygen is introduced into the injured plant tissue. When oxygen is present in cells, polyphenol oxidase (PPO) enzymes in the chloroplasts rapidly oxidize phenolic compounds naturally present in the apple tissues to o-quinones, colorless precursors to brown-colored secondary products.

How to Keep Apple Slices Fresh with Salt Water. Mix 1/2 teaspoon kosher salt into 1 cup of cool water until dissolved. Add your sliced apples and soak for about 10 minutes. Drain the apples and store in an airtight container for up to a week.

Fruit turns brown when exposed to air because a reaction is happening when a cut piece of fruit is exposed to oxygen. The chemical reaction can be simplified to: Polyphenol Oxidase + O2 → Melanin (Brown Color) Oxygen activates the compound polyphenol oxidase in the fruit to turn the fruit brown.

This unappetizing phenomenon is actually due to a chain of biochemical reactions known as “enzymatic browning.” When an apple is injured (or cut into pieces), the plant tissue is exposed to oxygen. This results in new chemicals (o-quinones), which then react with amino acids to produce brown-colored melanins.

This is because vitamin C is an antioxidant that reacts with the very reactive oxygen-centred radicals, turning them into less reactive species. Hence, this reduces the amount of oxidative damage to the apple flesh. This is why the apple in the vitamin C solution does not turn brown and remains fresh looking.

Oxygen in the air can cause sliced fruit to brown, a process called enzymic browning (an oxidation reaction). Phenols and the enzyme phenolase are found in the cells of the apple, and when these are exposed to oxygen in the air, for example through slicing, the oxygen causes a reaction.

Method #1: Lemon Juice To use this method to prevent apples from turning brown, create a water bath for your apple slices with a ratio of 1 tablespoon of lemon juice to 1 cup of water. Soak the apple slices for 3 to 5 minutes, then drain and rinse them.

brown

Called Opal apples, these non-browning apples are a hybrid between a Golden Delicious and the lesser-known Topaz apple. The reason Opal apples don’t turn brown is because they have lower levels of the enzyme that causes the flesh of apples to change color when exposed to oxygen.

Why do apples brown? Secondary browning generally refers to discoloration that occurs when an apple is beginning to decompose due to fungi and bacteria. In other words, when the fruit is rotting. Primary browning in apples takes place when the fruit’s phenolic compounds react with oxygen.

Using Water, Lemon Juice, and Citric Acid to Prevent Apples From Browning. One of the easiest things you can do to prevent browning is to submerge the cut fruit in plain water, which reduces the amount of air, and therefore oxygen, that can get to it.

This is known as enzymatic browning. Keep cut fruits, such as apples, pears, bananas, and peaches from turning brown by: Coating them with an acidic juice such as lemon, orange, or pineapple juice. Use a commercial anti-darkening preparation with fruits, such as Fruit-Fresh®*, and follow the manufacturer’s directions.

Consider a light coating. Spritz a light layer of lemon juice, lime juice, orange juice, or vinegar atop the fruit. For a sweeter flavor, you can lightly coat sliced bananas in a simple syrup and touch of lemon juice to prevent oxidation, Rushing adds, or lightly toss them in honey.

about 5 days

The United States Food and Drug Administration (FDA) recommends washing all fruits and vegetables under cold running water before preparation. Once fruits and vegetables are cut, chopped, or cooked, they should be refrigerated in covered containers or frozen in plastic freezer containers.

about 2 hours