Blueberries are a super food. New research shows that their antioxidant power becomes even stronger when the berries are frozen. The blue color of blueberries is given by the antioxidant Anthocyanins, which is present in their skin. South Dakota State Graduate student Marin Plumb discovered that freezing blueberries increases the amount of anthocyanin available for bodily absorption after they’re consumed. The freezing process creates ice crystals that change the biological plant structure making anthocyanin more available.