How to preserve watermelon

In this brief guide, we are going to answer the question “how to preserve watermelon” and discuss the different methods of preserving watermelon.

How to preserve watermelon

Presently, Asia accounts for more than 80% of worldwide watermelon production. China is the number one producer accounting for 67.6% worldwide. Africa, Europe, and North America have similar production output, around 3–4 million tonnes annually (1).

Watermelon can be preserved by :

• Storing uncut watermelon at room temperature
• Refrigerating cut watermelon

• Freezing cut watermelon
• Making pickles and preserves from the watermelon rind
• Dehydrating to make watermelon jerky

Why preserve watermelon

Watermelon is a seasonal fruit that is available in most countries for only a few weeks in the summer. Watermelons are also large so preserving allows them to be used later on and reduces wastage. Preserving watermelon allows it to be used up to 6 months later.

Preserving un-cut watermelon

The best way to store uncut watermelon is at room temperature. Whole watermelons must be placed in a cool dark place away from moisture. In fact whole, un-cut watermelon lasts longer at room temperature than in a fridge.

For short-term storage or transit to distant markets (>7 days), most recommendations use 7.2°C (45°F) and 85-90% R.H. as the acceptable handling conditions for watermelons. Watermelons are, however, prone to chilling injury at this temperature and extended holding at this temperature will induce chilling injury.  Shelf life for watermelon is 2-3 weeks at 10-15°C (50-60°F) depending on cultivar (2).

Refrigerating cut watermelon

Watermelon that has been cut can be stored in the refrigerator for a few days without spoilage. Fresh-cut processing of fruits promotes faster deterioration, since fruits are living tissues, they could be wounded and undergo enzymatic browning, off-flavor development, texture breakdown, and microbial contamination. Cut watermelon can be stored for 7 days in the refrigerator (3).

Make sure to wrap the watermelon in plastic wrap or place it in a covered container before storing it in the refrigerator. 

Freezing cut watermelon

Freezing watermelon will damage the fruit tissue and part of the nutrients will be lost. Watermelon is rich in Lycopene, a fat soluble carotenoid that has at least twice the antioxidant capacity of beta-carotene. Studies show that 10% of the lycopene amount of watermelon is lost after 30 days of frozen storage (4). 

To freeze watermelon :

• Wash and cut open the watermelon.
• Slice off the rind. Make sure to remove all the white and green areas until only the pink flesh remains.
• Cut the flesh into cubes or slices.
• Place the cut watermelon in a tray or cookie sheet that allows the pieces to freeze without touching each other.
• Once the pieces are frozen, transfer them to an airtight container or a ziplock bag.
• Label and place them back in the freezer until needed.

Making and preserves from watermelon rinds

Fermented pickles — also called crock pickles — are produced by curing fruit rind or vegetables in a salt brine for several weeks. During this treatment, salt-tolerant bacteria convert carbohydrates (sugars) in the vegetables into lactic acid by a process known as fermentation. Lactic acid preserves the pickles and gives them their characteristic tangy flavor. The salt concentration is very important in this process,and is necessary to encourage growth of the right types of bacteria (5).

Watermelon rinds can be preserved by the following method :

• Dice the watermelon rind into 1-inch cubes.
• Make a solution of 4 tablespoons of salt in 1 liter of water.
• Soak the cubes overnight in the solution.
• Drain off the excess liquid.
• Cook the rind until it is tender.

These cooked rinds can be used to make either pickles or preserves. There are several recipes for making watermelon pickles and preserves. 

For pickles :

• Make a pickling mixture from vinegar, sugar, cloves, cinnamon and mustard seed and alum.
• Boil the mixture.
• Allow the mixture to cool for about 15 minutes.
• All the rind and cook until the cubes are transparent.
• Remove from the heat and leave the rinds in the pickling mixture overnight, uncovered.
• Boil the rinds and the mixture once again.
• Pour into a clean jar. Leave about half an inch of space in each jar.
• Place the jars and lids in a water bath for 10 minutes.
• Remove from the water bath, cool and then seal the jars.
• Store the jars in a cool, dry place.
• Let the pickles sit for about a week before serving.

More information on this recipe can be found here.

For preserves :

• Make a mixture of water,  sugar, lemons sliced, cinnamon and cloves.
• Boil the mixture.
• Add the rind and cook until the cubes are transparent.
• Pour into clean jars and seal.
• Store the jars in a cool, dry place.

More information on this recipe can be found here. 

Dehydrating to make watermelon jerky

Drying is a creative way to preserve foods and use home-grown fruit, extra produce (e.g., ripe bananas) and roadside market specials. Like all methods of preservation, drying causes some nutrient loss. Pretreating fruits prior to drying is highly recommended. Pretreating helps keep light-colored fruits from darkening during drying and storage (6).

Watermelon can be easily dehydrated to make delicious watermelon jerky. The completed method can be found here.

To dehydrate watermelon :

• Wash and cut the watermelon.
• Slice off the rind and remove the seeds.
• Slice into thin slices of about a quarter-inch thickness.
• Sprinkle some salt if needed.
• Dehydrate at 135 degrees.
• The total dehydration time would be around 20 hours.
• Store the dehydrated watermelon jerky in an airtight container in a cool, dark place.

Shelf-life of preserved watermelon

• Un-cut watermelon: Uncut watermelon has a shelf-life of about 2 weeks when stored at room temperature in a cool, dark and dry place.
• Refrigerated watermelon: Watermelon can be cut and refrigerated for about 5 days.
• Frozen watermelon: Watermelon can be cut and frozen for about 6 months. 
• Pickled and preserved watermelon: Pickled and canned watermelon is shelf-stable for 1 year.
• Dehydrated watermelon jerky: Dehydrated watermelon generally has a shelf-life of 4 to 12 months, depending on the storage conditions.

How to tell if watermelon has gone bad

It is important to make sure that watermelon is not spoiled. 

Post-harvest deterioration of watermelon is linked to the activities of pathogenic fungi (A. flavus, Streptomyces spp. and F. oxysporum). Factors such as agrochemicals, rainfall, poor soil drainage, insect attacks, inappropriate harvest, transport, packaging and storage of watermelon fruits could contribute to post-harvest rot of watermelon. Mycotoxins produced by pathogenic fungi invasion on fruits could result in several diseases such as hypersensitivity and psychological disorder in man (7).

For uncut watermelon: Check the skin of the watermelon for any moldy patches and spots of black, blue or white.

For cut watermelon kept in the fridge or freezer: Check the flesh of the watermelon for spots and slime. Sometimes the watermelon may appear fine but emit a sour odor, this indicates spoilage. A sour taste also indicates spoilage. Any taste change can be a sign of spoilage.

Other FAQs about Watermelons that you may be interested in.

How to eat a watermelon?

How to tell if a watermelon is good?

How to Deseed a Watermelon

Conclusion

In this brief guide, we answered the question “how to preserve watermelon”. We discussed the different methods of preserving watermelon, along with the shelf-life obtained from each method. We also looked at how to identify watermelons that have gone bad.

References

1. Dube, J., G. Ddamulira, and M. Maphosa. Watermelon production in Africa: challenges and opportunities. Int J Vegetab Sci, 2021, 27, 211-219.
2. Özdemir, Ahmet Erhan, et al. Effects of rootstocks on storage and shelf life of grafted watermelons. J App Botan Food Qual, 2016, 89, 191-201.  
3. Sipahi, R. E., et al. Improved multilayered antimicrobial alginate-based edible coating extends the shelf life of fresh-cut watermelon (Citrullus lanatus). LWT-Food Sci Technol, 2013, 51, 9-15.  
4. Fish, Wayne W., and Angela R. Davis. The effects of frozen storage conditions on lycopene stability in watermelon tissue. J agric food chem, 2003, 51, 3582-3585.
5. Ingham, Barbara H. Homemade pickles & relishes. University of Wisconsin–Extension, Cooperative Extension, 2008.
6. Kendall, Pat, and J. Sofos. Drying fruits. Food and nutrition series. Preparation; 2007, 9,309.
7. ODELADE, Kehinde Abraham, and Oluwole Solomon OLADEJI. Isolation of phytopathogenic fungi associated with the post-harvest deterioration of watermelon fruits. Scient Afri 8, 2020, e00366.