Freezing preserves the fresh taste of summer-ripened peaches and plums for year-round enjoyment. Storing the fruits whole saves some of the effort when putting them up, and also gives you more options on how you'll use them later since they aren't already halved or diced. Whole frozen peaches and plums, especially when the peel is left on, are also juicier than the sliced variety after thawing.
Strip the Skin
Peaches and plums freeze well peeled or unpeeled, but whole fruits frozen without the peel may not be as juicy as those left unpeeled. If you do decide to peel before freezing, blanching makes this easier. Cut an X in the bottom of the peel with the tip of a paring knife then boil the peaches or plums for about 30 seconds. Cooling the fruit immediately after boiling stops the cooking process, then the peels slip off easily.
If you prefer to leave the skin on during freezing to help retain most of the fruit's juiciness, the fruits only need minimal preparation. Wash the peaches and plums thoroughly in cool water and remove the stems. Drying the fruits thoroughly prevents them from freezing together, so you can remove one at a time from the freezer. Fill a plastic bag with the washed fruits, press out the air and seal it closed. You can store the peaches and plums for 6 to 12 months in a 0-degree Fahrenheit freezer. When you're ready to use the fruit, run it under water, slip off the skin, then slice it as desired.
Bit of Sugar
A sugar pack helps preserve your fruits' flavor and texture. It works well for freezing peaches, especially if you plan to serve them whole or sliced from the freezer instead of using them in baked goods. Plums aren't as firm as peaches, so they aren't well-suited to dry-packing in sugar. Mix ¼ teaspoon ascorbic acid powder, which prevents browning, with 3 tablespoons of cold water and 2/3 cup sugar for every quart of peaches you are freezing. Toss the fruit with the mixture and pack it into jars or bags, leaving ½ inch of headspace before sealing closed and freezing. Thaw the peaches overnight in the refrigerator when you are ready to use them.
Plums and peaches both freeze well in syrup. Make a medium syrup for both peaches and plums by dissolving 3 cups of sugar and ¾ teaspoon ascorbic acid in 4 cups of water. Increase the sugar to 4 ¾ cups if you want a heavy syrup for plums. Pack your whole, peeled fruits in containers or bags to within 1 inch of the top, then add syrup to within ½ inch of the top. Seal the container or bag closed before storing the peaches or plums in the freezer.