A whole watermelon can be enormous. You cut a few slices for lunch, put the rest in the fridge and discover that everybody has had enough long before the fruit is finished. Freezing the surplus is a useful option, particularly for cold drinks. What it won't do is preserve the crisp, juicy texture of a fresh slice.
Watermelon contains a great deal of water. Ice crystals break down its cells, so thawed pieces tend to become soft and watery. Once you accept that, freezing makes sense: small cubes are excellent for blending, while frozen purée can be turned into an easy granita or slush.
Choose a sound ripe watermelon
Select fruit that feels firm and has no extensive soft spots, mould or leaking damage. A hollow-sounding tap isn't a reliable guarantee of ripeness.
If the watermelon has already been cut, check how it was stored. Fruit left sitting warm at a picnic for hours isn't a good candidate for freezing later.
Start with fresh suitable food. The freezer cannot reverse spoilage or make poorly handled cut melon safe again.
Wash the rind before cutting
Even though you probably won't eat the thick skin, wash the outside under running water. The knife can carry dirt from the rind into the flesh.
The US Food and Drug Administration specifically advises cleaning melons before cutting, including scrubbing firm produce with a clean brush where appropriate.
Dry the surface and use a clean board and knife. Keep raw meat and its juices away from the preparation area.
Cut the melon into stable sections
Slice off one end to create a flat resting surface if that helps. Cut the melon on a large stable board with a suitable sharp knife.
Remove the rind and divide the flesh into cubes that your blender or later recipe can manage.
Avoid trying to remove giant frozen wedges from a bag later. Small pieces give you much more flexibility.
Remove obvious seeds
Seedless watermelons often contain small pale immature seeds, which are generally soft. Dark hard seeds can be removed if the intended recipe needs a smooth texture.
Don't spend an hour picking out every tiny pale seed before blending. Your equipment and recipe may handle them without difficulty.
For serving children, always prepare pieces appropriate to age and follow feeding safety guidance.
Drain excess juice lightly
Freshly cut watermelon releases juice almost immediately. Let cubes sit briefly in a clean sieve so excessive liquid doesn't freeze into a large solid pool.
There's no need to squeeze the flesh. That would destroy the pieces before they reach the freezer.
You can freeze the collected clean juice separately in a suitable tray for drinks.
Tray-freeze the cubes
Line a freezer-safe tray with suitable baking parchment and spread the pieces in a single layer, leaving small gaps.
Place the tray level in a freezer operating at its recommended temperature, commonly around -18°C or colder.
Once the cubes are frozen firmly, transfer them promptly into freezer-rated packaging. This is easier than extracting a serving from one solid block.
Protect against freezer burn
Use a suitable airtight freezer bag or lidded container. Remove unnecessary air from bags without crushing the soft frozen pieces.
Label the pack with the fruit and date. Watermelon cubes can resemble other pale or pink fruit when covered in frost.
Avoid using thin packaging that tears when handled among other frozen items. Repeated air exposure can dull the flavour.
Freeze in realistic quantities
If you normally make a single smoothie, prepare single-smoothie packs. For a party, freeze several larger measured bags.
Don't store an entire watermelon in one enormous tub unless you genuinely need that amount in one go.
Portioning also prevents repeatedly warming a large bag while you try to separate cubes.
How to use frozen watermelon in smoothies
Add frozen cubes to a blender approved for frozen fruit, with some appropriate liquid if required. Blend until smooth.
Watermelon is already watery, so start with less additional liquid than you would use for frozen banana.
Lime juice or a little mint can complement its flavour. Taste before adding sugar because ripe watermelon is naturally sweet.
Make a simple slush
Blend frozen watermelon with a small amount of chilled juice or water until it becomes spoonable.
Work in batches to avoid overloading the blender motor. Stop and rearrange frozen chunks according to the appliance's instructions rather than forcing the blades.
Serve promptly. A homemade slush melts quickly, especially in a warm garden.
Make watermelon granita
Purée clean fresh watermelon and pour it into a shallow freezer-safe dish. Freeze until ice begins forming, then scrape periodically with a fork.
Continue scraping to build loose icy crystals. The process takes time, but it doesn't require an ice-cream machine.
A squeeze of lime can brighten the flavour. Adjust sweetness to the melon rather than adding sugar automatically.
Can frozen watermelon be eaten as cubes?
Yes, frozen cubes can be a refreshing snack for suitable eaters, but they are extremely hard straight from the freezer.
Don't give large rock-hard frozen pieces to small children or anyone at risk of choking. Allow safe softening or blend instead.
The texture after complete thawing won't resemble a fresh crisp cube, so choose the serving style carefully.
Why the texture becomes mushy
Watermelon cells contain a lot of liquid. When that water freezes, ice crystals disrupt the cell walls.
As the fruit warms again, juice escapes and the flesh loses its firmness. This is a normal physical change, not proof that the freezer is faulty.
No rinsing trick or extra sugar can restore the crisp structure of a freshly sliced watermelon.
What about freezing watermelon juice?
Strain or blend clean cut fruit as appropriate and pour the juice into freezer-safe containers with room for expansion.
Ice-cube trays make useful small portions for summer drinks. Move the frozen cubes into a sealed bag so they don't absorb freezer odours.
Watermelon juice may separate after thawing. Stir or shake a safely thawed portion before using.
Thaw only when needed
For smoothies and slushies, use the fruit directly from frozen. There is little point thawing it completely first.
For a sauce or drink needing thawed fruit, place the portion in a covered container in the refrigerator to catch released liquid.
Don't leave a bag of cut melon sitting on a warm counter overnight.
Safety with cut melon
Cut melon is perishable and needs appropriate refrigeration. Unlike a whole sound watermelon, cut flesh offers a moist environment where microorganisms can grow.
Freeze prepared fruit promptly after hygienic cutting. If cut melon was left at an unsafe temperature, don't assume freezing later makes it suitable.
Keep knives, containers and blenders clean, especially when food is going into drinks without further cooking.
When freezing isn't worth it
If you want attractive fresh slices for tomorrow's barbecue, refrigeration may be the better option.
Frozen melon shines when blended, puréed or turned into an ice dessert. It won't replace crisp wedges on a fruit platter.
The useful freezer routine
Wash the rind, cut sound fresh melon into cubes, drain briefly, tray-freeze and pack into labelled portions.
Use the cubes directly for smoothies and slushies. The freezer saves a surplus, provided you give up expecting thawed watermelon to behave like fresh fruit.