Sugar draws some moisture from the surface of fruit and forms a thin syrup around it. This layer limits contact with air, so the fruit browns and dries out less in the freezer. It also holds its texture better after thawing. You do not need this method for every fruit: fruit that will be cooked in a dish or dessert can be frozen without sugar.
Two things damage fruit in the freezer: air and drying. Air darkens cut surfaces, while dry freezer air draws moisture from the surface and shrivels the fruit. Sugar helps counter the 2 effects at once. Sprinkled over the fruit, it draws out some moisture and forms a thin syrup film around it; this film insulates the fruit from air and keeps moisture inside. The film also helps during thawing, allowing the fruit to release its juice gradually rather than all at once.
There are 2 ways to do this. Fruits with plenty of juice, such as strawberries and peaches, can be coated directly in sugar; they quickly form their own syrup and can then be placed in a container. Fruits with less juice, such as apples and pears, do not produce enough syrup with dry sugar alone. Pour separately prepared, cold sugar syrup over them and arrange the fruit so it is fully submerged in the syrup. If you use syrup, prepare it ahead of time and chill it in the refrigerator; warm syrup will cook the surface of the fruit. If the fruit does not stay under the syrup, place a folded piece of paper in the container to hold the fruit down.
Sugar alone is not enough for fruit that tends to brown. Apples, pears, peaches, and apricots start to brown as soon as they are cut; an enzyme reacting with air causes this. Adding a few drops of lemon juice to the syrup or sugar slows the reaction noticeably. Lemon also balances the flavor. Put the fruit into the mixture as soon as it is cut; fruit left on the counter will already have started to brown. Ready-made powdered mixes can do the same job instead of lemon, but lemon is usually enough for home cooking.
Not every fruit needs sugar, and this distinction matters. Fruit for smoothies, compote, jam, or cake can be frozen without sugar because its texture and color will change during cooking anyway. Fruit that stays whole in its skin, such as strawberries, blackberries, and sour cherries, also freezes well without sugar. Use sugar mainly when you want to preserve the fruit’s appearance and texture after thawing. Unsweetened frozen fruit releases more water when thawed; do not discard it—subtract it from the liquid in the recipe.
Containers and arrangement also affect the result. Put fruit in freezer bags with the air pressed out or in tightly sealed containers; empty space inside the container allows it to dry out. Filling bags in a thin, flat layer helps the fruit freeze faster. Label each bag or container with the fruit’s name and the date. Thaw fruit in the refrigerator and in its container; fruit thawed on the counter releases juice and falls apart. Store fruit that will be kept in the freezer for a long time toward the back, not the front, because the temperature near the door fluctuates whenever it is opened.