Summer in a Jar: Blackberry Jam

Fully ripe blackberries, although low in natural pectin and remarkably seedy, are filled with luscious flavor and a sweet perfume. In this recipe, apples contribute the necessary pectin, the seeds are removed, and the lemon juice nicely balances the flavor with a welcome tartness. Summer in a jar!

Season: Late summer

Yield: 6 cups

Store: Cool, dark pantry

6 cups ripe blackberries, picked over, rinsed, and drained

2 1/2 cups coarsely chopped tart apples, including skins and cores

1 1/2 to 2 cups water

Approximately 5 cups sugar

3 tablespoons lemon juice, or to taste

1. Crush the berries with a potato masher or whirl briefly in a food processor.
   
2. Place the crushed berries, apples, and 1 1/2 cups of the water in a preserving pan. Cook the mixture over medium heat, uncovered, until the fruit is very soft, 15 to 20 minutes. Stir often, adding additional water to keep the fruit from sticking.
   
3. Put the hot fruit through a food mill or fine strainer set over a bowl to remove the seeds. Rinse out the preserving pan.
   
4. Measure the remaining fruit pulp into the preserving pan and add 1 cup sugar for every cup of fruit; taste, adding enough lemon juice to make the fruit pleasantly tart.
   
5. Heat the mixture over medium-high heat to bring it rapidly to a boil, stirring constantly until the sugar dissolves. Cook the jam until it reaches 220°F on a kitchen thermometer or otherwise passes a jelly-doneness test. Remove from heat.
   
6. Carefully ladle the hot jam into hot, sterilized pint or half-pint jars, allowing 1/4  inch headspace. Follow the water-bath canning instructions below and process for 10 minutes.
   

Water-bath canning procedure

• Load the jars into the jar rack and, using the two handles, carefully lower it into the boiling water in the canning kettle. Adjust the water level so that it is at least 1 inch above the tops of the jars. Cover the canner with its lid.
  
• Start timing when the water returns to a full boil and process for the length of time indicated in your recipe. Do not allow the water to fall beneath the appropriate level or drop below a boil.