important. Cultivars Few named cultivars exist, and varieties differ mostly in the nature of the fruit: 'Branco' ("White") is a rare variety local to the Amazon estuary in which the berries do not change color, but remain green when ripe. This is believed to be due to a recessive gene since only about 30% of 'Branco' palm seeds mature to express this trait. 'BRS-Pará' was developed in 2004 by the Brazilian Agricultural Research Agency. The pulp yield ranges from 15% to 25%. 'BRS Pai d'Égua' is the newest cultivar developed by the Brazilian Agricultural Research Agency. Nutritional content A powdered preparation of freeze-dried açaí fruit pulp and skin was reported to contain (per 100 g of dry powder) 534 calories, 52 g carbohydrates, 8 g protein, and 33 g total fat. The carbohydrate portion included 44 g of dietary fiber with low sugar levels, and the fat portion consisted of oleic acid (56% of total fats), palmitic acid (24%), and linoleic acid (13%). The powder was also shown to contain (per 100 g) negligible vitamin C, 260 mg calcium, 4 mg iron, and 1002 IU vitamin A. Polyphenols A comparative analysis from studies reported that açaí has intermediate polyphenol content relative to 11 varieties of frozen juice pulps, scoring lower than acerola, mango, strawberry, and grapes. The extent to which polyphenols as dietary antioxidants may promote health is unknown, as no credible evidence indicates any antioxidant role for polyphenols in vivo. When three commercially available juice mixes, containing unspecified percentages of açaí juice, were compared for in vitro antioxidant capacity against red wine, tea, six types of pure fruit juice, and pomegranate juice, the average antioxidant capacity ranked lower than that of pomegranate juice, Concord grape juice, blueberry juice, and red wine. The average was roughly equivalent to that of black cherry or cranberry juice, and was higher than that of orange juice, apple juice, and tea. The medical watchdog website Quackwatch said that "açaí juice has only middling levels of antioxidants – less than that of Concord grape, blueberry, and black cherry juices, but more than cranberry, orange, and apple juices." The anthocyanins of açaí likely have relevance to antioxidant capacity only in the plant's natural defense mechanisms, and in vitro. Anthocyanins in açaí accounted for only about 10% of the overall antioxidant capacity in vitro. The Linus Pauling Institute and European Food Safety Authority state that "the relative