- 1/2 cup white sugar
- 1 tablespoon cornstarch
- 1/4 cup water
- 1/4 cup light corn syrup
- 2 teaspoons lemon juice, or more to taste
- 2 cups fresh blueberries
- 1 whole vanilla bean
- Combine sugar and cornstarch in a large pot. Pour in water, corn syrup, and lemon juice. Stir in blueberries and vanilla bean. Bring to a boil, reduce heat, and simmer until thickened and infused with vanilla flavor, about 5 minutes. Remove syrup from heat.
- Strain syrup into 3 hot, sterilized half-pint canning jars, filling to within 1/4 inch of the top. Wipe the rims of the jars with a moist paper towel to remove any residue. Top with lids and screw on rings.
- Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars into the boiling water using a holder. Leave a 2-inch space between the jars. Pour in more boiling water if necessary to bring the water level to at least 1 inch above the tops of the jars. Bring the water to a rolling boil, cover the pot, and process for 10 minutes.
- Remove the jars from the stockpot and place onto a cloth-covered or wood surface, several inches apart, until cool, about 1 hour. Press the top of each lid with a finger, ensuring that the seal is tight (lid does not move up or down at all). Store in a cool, dark area.