Attribute Details
Prep Time 25 minutes
Cook Time 1 hour 15 minutes
Total Time 1 hour 40 minutes (plus 8 hours chilling/cooling)
Skill Intensity Intermediate (Requires some patience and careful monitoring)
Yield 4 half-pint (8 oz) jars
Serving Size 1 Tablespoon (15g)
Ingredients
4 cups fresh watermelon, seeded and finely chopped (about half of a small seedless watermelon)
1/4 cup fresh lime juice (about 2-3 limes)
1/2 cup apple cider vinegar (5% acidity)
1 large jalapeño pepper, finely minced (seeds and ribs included for heat, removed for milder flavor)
1 teaspoon fresh ginger, grated
1/4 teaspoon red pepper flakes (optional, for an extra kick)
4 cups granulated sugar (use jam/preserving sugar if available)
3 tablespoons powdered pectin (such as Sure-Jell)
Zest of 1 lime
2 tablespoons fresh mint, finely chopped (optional, but recommended)
Equipment Needed
Large, heavy-bottomed pot (enameled cast iron or stainless steel)
Potato masher
Candy thermometer
4 half-pint canning jars with lids and rings
Large stockpot for water bath canning
Canning funnel
Jar lifter
The Recipe
Step 1: Prepare the Fruit
Begin by tackling the watermelon. Cut away the rind and dice the flesh into 1-inch cubes. Remove as many seeds as you can. Place the diced watermelon into a large, non-reactive bowl. Using a potato masher, gently crush the fruit. You are not looking for a puree; you want a chunky, juicy mixture with small pieces of melon remaining. You should have about 4 cups of this crushed mixture.
Step 2: The Flavor Base (The Soak)
Transfer the crushed watermelon to your large cooking pot. Add the minced jalapeño (decide your heat level now), grated ginger, lime zest, lime juice, and apple cider vinegar. Stir well. Add the red pepper flakes if you are seeking a fiercer burn.
Let this mixture rest for 10 minutes. This allows the pectin (which we will add later) to start activating with the acid, and lets the flavors begin to meld.
Step 3: The Boil (Patience Required)
Place the pot over medium-high heat and bring the mixture to a rolling boil—a vigorous boil that cannot be stirred down. Keep it there for exactly 10 minutes, stirring frequently to prevent sticking. The watermelon will release an enormous amount of liquid. Do not be alarmed. This is exactly what we want.
After 10 minutes, reduce the heat to a lively simmer. We are now on a mission to reduce. Cook for about 30–40 minutes, stirring occasionally, until the mixture has thickened significantly and the liquid has reduced by nearly half.
Pro-Tip: This is where the magic happens. You are concentrating the watermelon flavor. As the water evaporates, the sugars caramelize slightly, and the heat of the jalapeño becomes more pronounced.
Step 4: The Pectin and Sugar Addition
After the reduction, add the pectin and the sugar. Whisk constantly to dissolve. Bring the mixture back up to a full, roaring boil that cannot be stirred down. Once it reaches this boil, time it for exactly 1 minute.
Note: If using a candy thermometer, the mixture should reach 220°F (104°C) , which is the setting point for jam. If you do not have a thermometer, use the “wrinkle test”: place a small plate in the freezer. After a minute of boiling, drop a teaspoon of jam onto the cold plate. Return it to the freezer for 2 minutes. Run your finger through it. If it wrinkles and does not run back together, it is ready.
Step 5: The Finish (The Mint)
Remove the pot from the heat. Skim off any foam from the surface. Stir in the chopped fresh mint (if using). The residual heat will bloom the mint’s fragrance perfectly.
Canning for Shelf Stability (Recommended)
Sterilize: While the jam cooks, sterilize your jars in a boiling water bath for 10 minutes. Keep them warm.
Fill: Using your canning funnel, ladle the hot jam into the hot jars, leaving 1/4-inch of headspace at the top.
Seal: Wipe the rims of the jars with a clean, damp cloth. Place the lids and rings on, tightening to fingertip-tight (do not overtighten).
Process: Place the jars back into the boiling water bath. Ensure the water covers the jars by at least 1 inch. Bring to a rolling boil and process for 10 minutes (adjust for altitude).
Cool: Turn off the heat, remove the jars, and place them on a towel-lined counter. Do not disturb them for at least 8 hours, or overnight. You will hear the delightful “ping” of the lids sealing.
Refrigerator Storage: If you do not wish to water-bath can, simply store the jam in airtight containers in the refrigerator for up to 3 weeks.
How to Use This Jam
Cheese Board: Pair with Manchego, sharp cheddar, or a soft, creamy brie.
Glaze: Brush over grilled chicken or salmon during the last 5 minutes of cooking.
Breakfast: Swirl into oatmeal or spread on a toasted bagel with cream cheese.
Cocktails: Use a spoonful in a mezcal or tequila cocktail for a sweet-spicy kick.
Nutrition Facts
Per serving: 1 Tablespoon (15g)
Nutrient Amount
Calories 52
Total Fat 0g
Sodium 2mg
Total Carbohydrates 13.4g
Dietary Fiber 0.1g
Sugars 13.2g
Protein 0.2g
Vitamin C 2% DV
Iron 0.5% DV