Save those watermelon rinds from their usual fate on the compost or garbage heap! Instead, ferment them into a healthy treat to enjoy for months. Make fermented watermelons by combining the white inner rind of the already-eaten watermelon with salt and water. Leave the mixture at room temperature for one to two days and it ferments on its own into a slightly soured pickled watermelon. This natural fermentation process, called lacto-fermentation, uses bacteria present in the environment to break down sugars in the watermelon rind, while the salt acts as a preservative and helps to control the fermentation process.
Prepare the watermelon by removing all of the pink inner flesh, using a spoon. Use a knife to remove the outer green skin, leaving just the inner white rind. Cut the remaining rind into 1-inch pieces.
Mix a brine using 2 tablespoons of salt and 1 quart of water and stir until the salt is completely dissolved. Pack the watermelon rinds into the jar with the brine, ensuring the watermelon rinds are covered by at least 1 inch of brine. Add any spices you are using to the jar.
Cover the jar with a kitchen towel and secure the towel with a canning ring. Leave the jar on your counter for one to three days to ferment; the process should be done at room temperature, ideally between 60 and 70 degrees Fahrenheit.
Place the jar in your refrigerator, where your fermented watermelon rinds will keep for two to three months.
Use whatever whole spices you prefer for this recipe. Complementary choices for fermented watermelon include ginger, mustard seed, peppercorns, cayenne and garlic. Use just one, or a mixture for your watermelon ferment based on your own preferences.
If you don't have a canning ring, use a rubber band to secure the kitchen towel on the jar.
Ferment watermelon out of direct sunlight.
Try using fermented watermelon rind in watermelon kimchi. Just combine 1 cup of watermelon flesh, 1/2 cup of fish sauce, 1/2 medium onion, 6 garlic cloves, a 1-inch piece of fresh ginger and 1 tablespoon of sugar in a food processor and pulse to combine it all. Then, stir in 1 cup of Korean chili flakes (or more or less to taste for desired heat). Dry and chop the fermented watermelon rind into approximately 1-inch pieces and mix them in too. Top with some chopped scallion.
Measure the salt and water exactly when making any fermented product; the ratio of salt to water provides protection against harmful bacteria growth; measuring them incorrectly or carelessly can be dangerous.
Use clean utensils and containers when working with fermented foods to prevent contamination.