How to Keep Cut Fruit from Browning

The most effective way to keep cut fruit from browning is to expose the cut surface immediately to lemon juice, vinegar water, or lightly salted water. This acidic or salty environment slows the reaction that causes browning. Fruits such as apples, pears, bananas, avocados, and peaches turn brown within minutes of contact with air; this change does not mean the fruit has spoiled, only that a chemical reaction has occurred on the surface.

Why does fruit turn brown?
When fruit cells are cut, an enzyme and phenolic compounds that are normally kept in separate compartments come together and react with oxygen in the air. This reaction forms brown compounds on the surface; in cooking, the process is called enzymatic browning. The enzyme is highly active in fruits such as apples and pears, so the color change becomes noticeable within 5–10 minutes after cutting. In acidic fruits such as citrus and strawberries, the same enzyme is less effective, so browning proceeds much more slowly.

How do you use lemon juice and salt water?
Place the cut fruit in a bowl, drizzle it with a few drops of lemon juice, and toss gently; the acid in lemon disrupts the conditions for the reaction that causes browning. The same process can be done by soaking the fruit for a few minutes in lightly salted water made by dissolving one 5 ml measure of salt in a 200 ml measure of water. Do not leave fruit in the salt water for more than 3–5 minutes; then drain and rinse it lightly, or it may taste slightly salty. Use only a small amount of lemon juice, or it may overpower the fruit’s own flavor.

Which fruits brown faster?
Apples, pears, bananas, and avocados are among the fruits that brown most quickly and should be treated immediately after cutting. Peaches and nectarines also brown quickly, especially when left in a warm place. Strawberries, grapes, watermelon, and citrus fruits have a high natural acid content, so they retain their color for a long time even at room temperature and generally do not need additional treatment. Pears brown a little more slowly than apples but still belong to this group.

Other ways to prevent browning
Storing cut fruit in a tightly closed, airtight container also slows browning because less oxygen is available for the reaction. Stretching plastic wrap tightly over the fruit so it touches the surface has the same effect. Keeping fruit cold in the refrigerator slows the reaction but does not stop it completely; for best results, cut the fruit close to serving time.

Does browning matter for fruit that will be cooked?
A few minutes of browning is practically unimportant for fruit that will be cooked, such as in compote, jam, or tart filling; heat will change the fruit’s color and texture anyway. Therefore, fruit intended for cooking can go directly into the pot after cutting instead of being placed in water or lemon water first. Browning is generally not a problem when fruit is juiced either, since juicing breaks down the fruit and turns it into liquid, changing the color anyway. Browning matters most when fruit will be served raw and visibly, such as on fruit platters, in salads, or as a pastry garnish.