Yield: approximately 15 half pints
20 oranges, washed
8 cups sugar
3 packages low sugar pectin
4 cups cranberry juice
3 cups cranberries, sorted and washed
Using a medium cheese grater, remove the zest from the fruit. Combine the zest in a large stainless steel or enameled cast iron pot with 4 cups of cranberry juice. Bring to a boil, reduce temperature to medium high and simmer for half an hour.
While the zest cooks, squeeze the juice from the oranges. Set the membranes and any seeds aside.
When all the fruit has been broken down, bundle the reserved pith and seeds into a length of cheesecloth, tying the cloth well so that no seeds can escape.
Mix the pectin into the sugar. Add the orange juice, cranberries, sugar mix and the cheesecloth bundle to the cooked mixture.
Stir constantly as you bring to a boil and cook vigorously until the mixture reaches 220 degrees (this takes between 30-40 minutes). Remove the cheesecloth bundle after about 30 minutes and squeeze juice out, return juice to the pot.
When the marmalade reaches 220 degrees and sustains it for one minute, remove the pot from the heat. Stir for about a minute off the heat, to help the zest bits become evenly spread throughout the preserves.
Fill sterilized jars to 1/4" of top, wipe rims, apply sterile lids and screw rings. Lower into a prepared boiling water bath and process for five minutes at a gentle boil (do not start counting time until the pot has achieved a boil).
Remove jars from the pot and let them cool completely. When they are cool, check the seals by pushing down on the top of the lid. Lack of movement means a good seal.