Superfruit: Acai Berry

The Acai palm (Euterpe oleracea) is a species of palm tree in the genus Euterpe cultivated for their fruit and superior hearts of palm.  Its name comes from the European adaptation of the Tupian word '[fruit that] cries or expels water'. Global demand for the fruit has expanded rapidly in recent years, and acai is now cultivated for that purpose primarily. The closely-related species Euterpe edulis (jucara) is now predominantly used for hearts of palm.

Eight species are native to Central and South America, from Belize southward to Brazil and Peru, growing mainly in swamps and floodplains. Acai palms are tall, slender palms growing to 15–30 meters, with pinnate leaves up to 3 meters long.

Acai (pronounced ah-sah-EE) berry is the fruit of the Acai palm, a small, round, black-purple drupe about 1 inch (25 mm) in circumference, similar in appearance but smaller than a grape and with less pulp, is produced in branched panicles of 500 to 900 fruits. Two crops of fruit are produced each year. The fruit has a single large seed about 0.25–0.40 inches (7–10 mm) in diameter. The exocarp of the ripe fruits is a deep purple color, or green, depending on the kind of acai 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 Brazilian Amazon, acai palm was described as the most important plant species because the fruit makes up a major component of their diet, up to 42% of the total food intake by weight.

In the northern state of Para, Brazil, acai pulp 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). Acai has become popular in southern Brazil where it is consumed cold as acai na tigela ("acai in the bowl"), mostly mixed with granola. Acai is also widely consumed in Brazil as an ice cream flavor or juice. The juice has also been used in a flavored liqueur. Since the 1990s acai juice and extracts are used globally in various juice blends, smoothies, sodas, and other beverages.

Recently, the Acai berry has been marketed as a dietary supplement. Companies sell Acai berry products in the form of tablets, juice, smoothies, yogurt, instant drink powders and whole fruit.  

Nutritional content

A powdered preparation of freeze-dried acai fruit pulp and skin (Opti-acai, K2A, Inc.) was  reported to contain (per 100 g of dry powder) 533.9 calories, 52.2 g carbohydrates, 8.1 g protein, and 32.5 g total fat. The carbohydrate portion included 44.2 g of dietary fiber and low sugar value (pulp not sweet). The powder was also shown to contain (per 100 g): negligible vitamin C, 260 mg calcium, 4.4 mg iron, and 1002 U vitamin A, as well as  aspartic acid and glutamic acid; the amino acid content was 7.59% of total dry weight.

The fat content of acai consists of oleic acid (56.2% of total fats), palmitic acid (24.1%), and linoleic acid (12.5%). Acai also contains beta-sitosterol (78–91% of total sterols). The oil compartments in acai fruit contain polyphenols such as procyanidin oligomers 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.

Polyphenols in raw materials

A comparative analysis from in vitro studies reported that acai has intermediate polyphenol content and antioxidant potency among 11 varieties of frozen juice pulps, scoring lower than acerola, mango, strawberry, and grapes.

A powdered preparation of freeze-dried acai fruit pulp and skin was shown to contain  anthocyanins (3.19 mg/g); however, anthocyanins accounted for only about 10% of the overall antioxidant capacity in vitro. 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). A study on another different freeze-dried acai product (Opti- Acai) reported that the formulation contained much lower levels of anthocyanins, proanthocyanadins, and other polyphenol compounds as compared with blueberries and other antioxidant-rich fruits.

In an in vitro study of different acai varieties for their antioxidant capacity, a white one displayed no antioxidant activity against different oxygen radicals, whereas the purple variety most often used commercially had antioxidant activity against peroxyl radicals and to a lesser extent peroxynitrite but little activity against hydroxyl radicals. 

Freeze-dried acai powder was found to have antioxidant activity in vitro against superoxide (1614 units/g) and peroxyl radicals (1027 μmol TE/g) and mild 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. These results, however, apply only to in vitro conditions and remain unknown for whether they are physiologically relevant. Rather, more subtle, non-antioxidant roles in vivo are likely.

Extracts of acai seeds were reported to have antioxidant capacity in vitro against peroxyl radicals, similar to the antioxidant capacity of the pulp, with higher antioxidant capacity against peroxynitrite and hydroxyl radicals.

Antioxidant potential of juice

When three commercially available juice mixes containing unspecified percentages of acai berry 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 was 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.

A study in 12 healthy fasted human volunteers demonstrated that blood antioxidant capacity was increased within two hours after consumption of a commercial acai berry juice beverage or applesauce, but did not investigate any physiological effect of these supposed antioxidants. The generation of reactive oxygen species was not significantly affected by acai berry juice consumption.

Source, Images: http://en.wikipedia.org/wiki/Acai_palm