Fresh, juicy oranges aren't the most perishable of fruit, but they can begin to lose some of their charm in as little as a week. If you've invested in a large quantity of the fruit, or have the good fortune to enjoy a backyard orange tree, that might sometimes mean you've got more than you can conveniently use while they're still at their best. They can be canned, dried or turned into jam, but freezing is a better way to preserve their fresh flavor.
Wash your hands, utensils and work surfaces scrupulously before you start, to minimize the risk of cross-contamination. Oranges aren't prone to carrying bacteria, but once cut -- like other foods -- are susceptible to infection from outside.
Wash the oranges carefully under cold running water, using no soap or bleach. Dry them carefully with fresh paper towels and lay them on a clean cutting board.
Peel the oranges and separate them into segments, or slice them crosswise into rounds. For a finished, professional appearance, cut the peel and outer membrane from the oranges with a sharp knife to reveal the colorful flesh. Cut away the segments from their membranes, leaving the membrane-free flesh -- called "supremes" by chefs -- cleaned and ready to use.
Dry Pack Method
Count enough freezer-safe canning jars or food-grade plastic containers to hold your oranges. Wash and rinse them in plenty of hot, soapy water, then dry them with clean paper towels.
Pack the orange segments or slices tightly into each container, arranging them carefully to exclude as much air as possible. The less oxygen can reach the segments, the longer they'll retain their quality.
Seal the jars or containers, leaving 1/2 inch of headspace to allow for the oranges to expand as they freeze.
Arrange the jars or containers in a single layer, distributing them evenly around your freezer. This speeds the freezing process, helping maintain the oranges' quality.
Prepare a heavy, canning-style syrup by boiling 2 parts sugar to 3 parts water, by volume. The syrup should be at refrigerator temperature when you use it, to speed freezing, so do this step ahead of time.
Pack your orange slices or segments into freezer-safe canning jars or food-safe plastic containers.
Pour cold syrup over the oranges until they're submerged, leaving 1/2 to 3/4 inch of headspace to allow for expansion when they're frozen. Add crumpled wax paper to the top of the jar to submerge the oranges and seal the container.
Arrange the jars or containers in your freezer, leaving plenty of space between them where air can circulate and chill the contents quickly.