Jam can be made using frozen berries that are not frozen with syrup; the first step is to defrost the berries so they can be hulled and moderately crushed, but not completely pulverized unless a seedless jam is desired. Crushing releases some of the fruit's natural pectin. The jam maker should make sure that he or she has enough frozen strawberries to yield about six cups after defrosting and crushing.
- Step 1: Sanitize the jam jars and lids. Both the jam jars and lids should be washed thoroughly in hot, soapy water.
- Step 2: Measure out the sugar according to pectin package directions. Low-sugar pectin typically requires four cups of sugar, while regular pectin requires seven.
- Step 3: Mix the berries and pectin together and cook according to pectin package directions.
- Step 4: Add the sugar to the berry-pectin mix and bring to a boil for one minute, skimming off any large amounts of foam that accumulate.
- Step 5: Test the jam for thickness. Use a chilled metal spoon to assess the consistency of a small amount of cooled jam; if it's not thick enough, stir in more pectin.
- Step 6: Fill the jars with jam, then add lids and rings and process according to proper sanitary guidelines.