Watermelon tastes best when sliced just before serving. Its thick, fibrous rind provides more than enough protection to prevent oxidation, the primary factor contributing to quality reduction and spoilage. You can also freeze watermelon indefinitely.
You can store sliced watermelon in the freezer for 10 to 12 months, but you'll find the structural quality suffers a bit. But this isn't necessarily a bad thing – thawed watermelon might not have the crispness fresh watermelon has, but you can use it in an array of dishes that don't rely on its texture, such as cocktails, smoothies, granitas and even frozen yogurt.
You can slice watermelon into large chunks or cubes, or use a melon baller, whichever works best for you. Remove the seeds as you cut the watermelon. Alternatively, puree the seedless watermelon flesh and pour it into ice cube trays for freezing.
Freeze the watermelon as quickly as possible after cutting to help maintain its structure. Arrange the pieces on a sheet pan lined with wax paper or parchment paper, spacing the pieces at least 1/4 inch apart. Set the pan in the freezer until the watermelon freezes solid, 20 to 30 minutes depending on your freezer and how full it is.
Pack the frozen watermelon pieces in heavy-duty freezer bags and store them in the freezer until ready to use.
Uses for Frozen Watermelon
Other than snacking, there are scores of dishes you can use frozen watermelon in. Try some of the following when you're ready for a watermelon treat – in season or out!
To make watermelon frozen yogurt, puree 2 cups of Greek-style yogurt along with 1 cup frozen watermelon and agave syrup to taste. As an alternative to agave syrup, mix 2 parts sugar with 1 part water until the sugar dissolves. Add the puree to a freezer-safe plastic container, and chill it in the freezer for 1 hour, stirring it every 15 minutes.
For a watermelon granita, puree 2 cups frozen watermelon, half a frozen banana, 1/2 cup of water, 1/2 cup of ginger ale and 2 tablespoons equal parts sugar and water. If needed, freeze for 15 minutes and stir before serving.
To mix a watermelon daiquiri, blend 4 cups of frozen watermelon, 1/4 cup orange liqueur, 1/2 cup of light rum, 1/4 cup of lime juice and 1 cup of ice cubes; garnish with a watermelon wedge.