The açaí palm is a member of the genus Euterpe, which contains 7 species of palms native to tropical Central and South America, from Belize south to Brazil and Peru, growing mainly in floodplains and swamps.
The genus is named after the muse Euterpe of Greek mythology. Euterpe are tall, slender palms growing to 15-30 meters, with pinnate leaves up to 3 meters long. Many of the palms that were once in the genus Euterpe have been reclassified into the genus Prestoea (Riffle, 2003). The species Euterpe oleracea is usually called Açaí Palm, after the Portuguese derivation of the Tupian word ïwasa'i, 'fruit that cries or expels water'.
The fruit, 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, is produced in branched panicles of 700 to 900 fruits. Two crops of fruit are produced each year. The fruit has a single large seed about 0.25-0.40 inch (7–10 mm) in diameter. The exocarp of the ripe fruits is a deep purple color, or green, depending on the kind of açaí and its maturity. The mesocarp is pulpy and thin, with a consistent thickness of 1 mm or less. It surrounds the voluminous and hard endocarp which contains a seed with a diminutive embryo and abundant endosperm. The seed makes up about 80% of the fruit (Schauss, 2006c).
The berries are 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).
The juice and pulp of açaí fruits (Euterpe oleracea) are frequently used in various juice blends, smoothies, sodas, and other beverages. In northern Brazil, açaí (or jussara, which is one of the fruit's common folk names) is traditionally served in gourds called "cuias" with tapioca and, depending on the local preference, can be consumed either salty or sweet (sugar, rapadura and honey are known to be used in the mix). Açaí has become popular in southern Brazil where it is consumed cold as açaí na tigela ("açaí in the bowl"), mostly mixed with granola — a fad in which açai is considered an energizer. Açaí is also widely consumed in Brazil as an ice cream flavor or juice.
As the high fat content of açaí (Nutritional content, below) indicates it would deteriorate rapidly after harvest, its raw material is generally available outside the immediate growing region only as juice or fruit pulp that has been frozen or processed as a pulp powder or freeze-dried powder. Several companies now manufacture juices, health drinks, yoghurts, and sorbets made from açaí berries, often in combination with other fruits.
Apart from the use of its berries as food, the açai palm has other commercial uses. Leaves may be made into hats, mats, baskets, brooms and roof thatch for homes, and trunk wood, resistant to pests, for building construction (Silva, 2005).
Comprising 80% of the berry mass, seeds may be ground for livestock food or as a component of organic soil for plants. Planted seeds are used for new palm tree stock which, under the right growing conditions, requires months to form seedlings.
Açaí has an exceptional content of fats, including oleic acid (56.2% of total), palmitic acid (24.1% of total), and linoleic acid (12.5% of total), and also contains a high amount of beta-sitosterol (78-91% of total sterols). These oil compartments in açaí fruit harbor dense contents of polyphenols such as procyanidin oligmers and vanillic acid, syringic acid, p-hydroxybenzoic acid, protocatechuic acid, and ferulic acid which were shown to degrade substantially during storage or exposure to heat.
A powdered preparation of freeze-dried açaí fruit pulp and skin was shown to contain anthocyanins (3.19 mg/g), including cyanidin 3-glucoside and cyanidin 3-rutinoside, yet the contribution of anthocyanins to overall antioxidant capacity of açaí is only about 10%. The powdered preparation was also reported to contain twelve flavonoid-like compounds, including homoorientin, orientin, taxifolin deoxyhexose, isovitexin, scoparin, as well as proanthocyanidins (12.89 mg/g), and low levels of resveratrol (1.1 μg/g).
In a study of different açaí varieties for their antioxidant capacity, a white species displayed no antioxidant activity against different oxygen radicals, whereas the purple variety most often used commercially was excellent against peroxyl radicals, good against peroxynitrite and poor against hydroxyl radicals.
Freeze-dried açaí powder was found to have high antioxidant activity against superoxide (1614 units/g) and peroxyl radicals (1027 μmol TE/g) and milder activity for peroxynitrite and hydroxyl radicals. The powder was reported to inhibit hydrogen peroxide-induced oxidation in neutrophils, and to have a slight stimulatory effect on nitric oxide production by lipopolysaccharide-stimulated macrophages in vitro.
Extracts of açaí seeds were reported to have antioxidant capacity against peroxyl radicals, similar to the capacity of the pulp, with higher antioxidant capacity against peroxynitrite and hydroxyl radicals.
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 with added antioxidants (provided by Pom Wonderful, the sponsor of the study), the average antioxidant capacity was ranked lower than that of the antioxidant enhanced 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.
Studies have demonstrated that blood antioxidant capacity increases within two hours of consuming a commercial açaí juice.
Freeze-dried açaí powder was shown to have mild inhibitory effects on cyclooxygenase enzymes COX-1 and COX-2, and chemically-extracted polyphenolic-rich fractions from açaí were reported to reduce the proliferation of HL-60 (experimental leukemia) cells in vitro. In vitro anti-proliferative effects were also observed with extracts from açaí pulp oil.
Orally-administered açaí has been tested as a contrast agent for magnetic resonance imaging of the gastrointestinal system. Its anthocyanins have also been characterized for stability as a natural food coloring agent.