In a large stockpot, cover the mayhaws with water and bring to a boil. Reduce heat, cover, and simmer for 30 minutes. Remove from heat and strain berries and juice through a chinois or a colander. Extract the remaining juice from the berries with a pestle if using a chinois or with the back of a spoon if using a colander. Strain the juice two times through two or three layers of cheesecloth or a jelly bag.
Yield: approximately 12 cups juice. Juice may be frozen and used up to one year later.