Blackberry jam recipe in the canning category

: Wash berries and cook in saucepan over moderate heat until juice begins to flow and berries are soft. Run through a food mill to obtain juice and pulp. Measure out 4 cups of juice and pulp mixture and place in preserving pot. Bring to a boil. Add sugar and cook over moderate heat until candy thermometer reaches about 220 degrees F, about 30 minutes. Pour into jars and seal. Extra juice and pulp may be kept in refrigerator for 2 weeks or frozen for making another batch of jam later.