The fruit, is a small, round, black-purple drupe about 1 inch (25 mm) in diameter, similar in appearance and size to a grape but with less pulp. The berries are also harvested as food. In a study of three traditional Caboclo populations in the Amazon region of Brazil, açaí palm was described as the most important plant species because the fruit makes up such a major component of diet (up to 42% of the total food intake by weight) and is economically valuable in the region (Murrieta et al., 1999).
Nutritional Content
A recent study using modern procedures and a standardized freeze-dried açaí fruit pulp and skin powder found nutrient analysis results from 100 g (3.5 ounces) of powder to equal 533.9 calories, 52.2 g carbohydrates, 8.1 g protein and 32.5 g total fat. The carbohydrate portion includes 44.2 g of fiber (Schauss et al. 2006a). Having nearly one-third of its mass as dietary fiber, açaí is an exceptional source of this valuable macronutrient: a 100 g serving of the powder would provide all the recommended fiber needs for adults (20-30 g per day).
Açaí is particularly rich in fatty acids, feeling oily to the touch. It contains high levels of the monounsaturated fatty acid oleic acid (56.2% of total fats). It is also rich in palmitic acid (24.1% of total fats, a saturated fat) and the polyunsaturated omega-6 fatty acid linoleic acid (12.5% of total fats). (Schauss et al. 2006a). β-sitosterol (beta-sitosterol), a phytosterol that competes with dietary cholesterol for absorption and so may reduce blood cholesterol levels, is also unusually rich (78-91% of total sterols) (Lubrano, 1994; Schauss 2006a).
A later study found vitamin C content was negligible, calcium levels of 260 mg, iron to be 4.4 mg and vitamin A equal to 1002 IU per 100 g of dry weight (Schauss et al. 2006a). A recent study found 19 amino acids in pulp and skin powder, with especially high contents of aspartic acid and glutamic acid. The amino acid content totalled 7.59% of the total dry weight (Schauss et al. 2006a).
Antioxidant Phytochemicals
The dense pigmentation of açaí has led to several experimental studies of its anthocyanins, a group of polyphenols that give the deep color to berries, other fruits and vegetables and are high in antioxidant value under active research for potential health benefits[1]. A recent study using a standardized freeze-dried açaí fruit pulp and skin powder found the total anthocyanin levels to be 319 mg per 100 grams (Schauss et al., 2006a). Cyandin 3-glucoside and cyanidin 3-rutinoside are major açaí anthocyanins [2].
Twelve other flavonoid-like compounds were additionally found in the Schauss et al. 2006a study, including homoorientin, orientin, taxifolin deoxyhexose, isovitexin and scoparin, as well as several unknown flavonoids. Proanthocyanidins, another group of polyphenolic compounds high in antioxidant value, totalled 1,289 mg per 100 grams of the freeze-dried pulp/skin powder, with a profile similar to that of blueberries (Schauss et al., 2006a). Resveratrol was additionally found to be present in acai in this study, although at low levels of 1.1 microgram per gram.
A number of studies have measured the antioxidant strength of açaí. Unfortunately, the sources of açaí and preparations (e.g., whole fruit, juice, extract or soluble powder) for reporting the results vary. A recent report using a standardized oxygen radical absorbance capacity or ORAC analysis on a freeze-dried açaí powder found that this powder showed a high antioxidant effect against peroxyl radical (1027 micromol TE/g). This is approximately 10% more than lowbush blueberry or cranberry on a dry weight basis (Wu, 2004). The ORAC value for this freeze-dried powder was significantly higher than when other methods of drying the fruit were tested (Schauss, 2006c).
The freeze-dried powder also showed very high activity against superoxide, with a SOD assay level of 1614 units/g. Superoxide is thought to be the initial producer of other more potent reactive oxygen species, and thus protection against it is very important as a first line of defense for the body. Antioxidant activity against both peroxynitrite and hydroxyl radicals was also observed, although effects were milder than that seen against peroxyl radical and superoxide. Additionally, antioxidant molecules from the freeze-dried powder were shown to actually enter freshly obtained human neutrophils and inhibit oxidation induced by hydrogen peroxide, even at very low concentrations of the açaí powder including 0.1 part per trillion (Schauss et al., 2006b). A previous report using a total oxygen scavenging capacity assay also found that açaí has extremely high antioxidant effects against peroxyl radical, as well as a high capacity against peroxynitrite, and a moderate capacity against hydroxyl radical when compared with other fruit and vegetable juices[3] .
Antioxidant values of the seeds of the açaí fruit have also been reported (Rodrigues, 2006). Similarly to the berries, the antioxidant capacity of the seeds were strongest against peroxyl radicals, at a concentration in the same order of magnitude as the berries. The seeds had a stronger antioxidant effect than the berries for peroxynitrite and hydroxyl radicals, although still less than its effects against peroxy radical.
Reference:
Lubrano, C., Robin, J. R., and Khaiat, A. (1994). Fatty-acid, sterol and tocopherol composition of oil from the fruit mesocarp of 6 palm species in French-Guiana. Oleagineux 49: 59-65.
Murrieta, R. S. S., Dufour, D. L. and Siqueira, A. D. 1999. Food consumption and subsistence in three Caboclo populations on Marajo Island, Amazonia, Brazil. Human ecology 27: 455-475
Rodrigues, R. B., Lichtenthaler, R., Zimmermann, B. F., Papagiannopoulos, M., Fabricius, H., Marx, F., Maia, J. G. and Almeida, O. (2006). Total oxidant scavenging capacity of Euterpe oleracea Mart. (acai) seeds and identification of their polyphenolic compounds. J. Agric. Food Chem. 54: 4162-4167.
Schauss, A. G., Wu, X., Prior, R. L., Ou, B., Patel, D., Huang, D., & Kababick, J. P. (2006a). Phytochemical and nutrient composition of the freeze-dried amazonian palmberry, Euterpe oleraceae Mart. (acai). J. Agric. Food Chem. 54 (22): 8598-8603.
Schauss, A. G., Wu, X., Prior, R. L., Ou, B., Huang, D., Owens, J., Agarwal, A., Jensen, G. S., Hart, A. N., & Shanbrom, E. (2006b). Antioxidant capacity and other bioactivities of the freeze-dried amazonian palm berry, Euterpe oleraceae Mart. (acai). J. Agric. Food Chem. 54 (22): 8604-8610.
Schauss, A. G., (2006c). Acai (Euterpe oleracea): An Extraordinary Antioxidant-Rich Palm Fruit. Biosocial Publications
Wu, X., Beecher, G.R., Holden, J.M., Haytowitz,D.B., Gebhardt, S.E., & Prior, R.L. (2004). Lipophilic and Hydrophilic Antioxidant Capacities of Common Foods in the United States. J. Agric. Food Chem. 52 (12): 4026-4037