From the Kitchen Window column

I included pectin in my blackberry jam recipe because I was worried about my jam not setting enough. Leave it out if you prefer. If you choose to skip the pectin, you'll need to cook the jam longer, perhaps a half-hour or so, and can reduce the amount of sugar if you wish. It's best to make jam in small batches, so try doubling this recipe in a few pots if you have a lot of berries and wish to make a lot of jam.

Makes 2 cups

1 pound fresh blackberries (4 cups)

Juice of one small lemon

2 tablespoons powdered fruit pectin

1 cup sugar

Bring a large pot of water to a boil.

In a medium-sized pot, mash blackberries with a potato masher or a fork. Over low heat, stir in the lemon juice and the pectin. Bring to a rolling boil and add the sugar, stirring until it dissolves. Return to a boil and boil rapidly for about 15 minutes, skimming off the foam and discarding, until the mixture thickens.

Pour the jam into sterilized jars, leaving about 1/4-inch space at the top. Wipe the rims clean. Apply lids and clamp or screw on tightly. Process in a water bath (the large pot of boiling water) for 10 minutes.

Remove from water bath and set aside, letting cool to room temperature, about 8 hours (the jam will further set as it cools). Press on each lid. If a lid springs back, it is not sealed and refrigeration is necessary. [Copyright 2011 National Public Radio]