Salvaging Frozen Grapefruit. If your grapefruit did freeze on the tree, pick it immediately. After a freeze, the only use for the fruit is for the juice. Juice the freeze-damaged grapefruit and freeze the juice in ice cube trays for use in recipes. The grapefruit juice ice cubes can also be used for flavoring plain or sparkling water or to keep a citrus punch cool without diluting it.