The açaí palm (pronounced [asaˈi]) 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, attractive 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 Tupi word ïwasa'i, fruit that cries or expels water. The vernacular name is also sometimes spelled Assai Palm in English.
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 per year. The fruit has a single large seed about 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.[citation needed] The seed makes up about 80% of the fruit (Schauss, 2006c).
Harvesting and uses
Stem
Heart of palm, the soft inner growing tip of some palms (Euterpe edulis, Euterpe oleracea, Bactris gasipaes), is often consumed in salads.[citation needed]
Fruit
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).
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 where açai is considered as an energizer. Açaí is also widely consumed in Brazil as an ice cream flavor or juice.
As açaí deteriorates rapidly after harvest, its raw material is generally only available outside the immediate growing region as juice or fruit pulp that has been frozen, dried, or freeze-dried. However, several companies now manufacture juices, other health drinks, and sorbets made from açaí berries, often in combination with other fruits.
[edit] Other uses
Apart from the use of its berries as food, the açai palm has other purposes. Leaves may be used for making 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 only months to form seedlings, although açaí palm has not been successfully cultivated outside of South America (Schauss, 2006c). Seeds are also used to make a variety of jewelry and souvenirs[citation needed].
In traditional medical practices, fruit and roots have been used for treating gastrointestinal problems and sap as an astringent[citation needed]. The seeds are a source of polyunsaturated and saturated fatty acids (see below; Plotkin, 1984; Silva, 2005; Schauss et al., 2006a).
[edit] Nutritional content
Several early studies done on the nutritional composition of açaí were summarized by Rogez in a 2000 book in Portuguese entitled "Açaí: Preparo, Composição e Melhoramento de Conservação" (Schauss et al. 2006a). Other previous studies dating back to the 1930s and 40s were not always in agreement on nutritional contents.
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).
Due to the large amount of waste that accumulates during the harvesting of the hearts of palm, sawdust from the left-over trunks of the açaí palms have been analyzed for possible uses including energy utilization. The inner layer of the trunk is mineral rich, and is significantly higher in all the minerals that were tested including sodium, potassium, calcium, magnesium, and iron compared to the outer layer of the tree. This inner layer could potentially be used as a source for these minerals. Ash content (often used as an alkaline source for saponification or in plant fertilizers) was also higher in the inner section of the tree. Levels of lignins, cellulose, holocellulose and gross heat production were slightly higher in the outer trunk layers, and cellulose levels were fairly high overall (Dyer, 1996).
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). Other powders with ORAC values this high include cinnamon (2675 micromol TE/g), cloves (3144 micromol TE/g), turmeric (2001 micromol TE/g) and dried oregano (1593 micromol TE/g) (Wu, 2004).
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] .
Only 10% of açaí's high antioxidant effects could be explained by its anthocyanin content[4], indicating that other polyphenols contribute most of the antioxidant activity. Schauss et al. similarly found that that ratio of the hydrophilic ORAC levels to the total phenolics in the freeze-dried fruit was 50, a higher value than the typical fruit and vegetable ratio of 10[citation needed].
Schauss et al. (2006b) also utilized the "Total Antioxidant" or TAO assay to differentiate the "fast-acting" (measured at 30 seconds) and "slow-acting" (measured at 30 minutes) antioxidant levels present in freeze-dried powder. Acai was found to have a higher "slow-acting" antioxidant components, suggesting a more sustained antioxidant effect compared to "fast-acting" components.
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. The results of this study were not linear based on the concentration of the seeds that were used. The authors suggest the future use of the seeds (a by-product of juice making) for antioxidant benefits such as prolonging shelf-life of foods.
Other Research
Açaí, in the form of a specific freeze-dried fruit pulp, was shown to have mild inhibitory effects on cyclooxygenase enzymes COX-1 and COX-2 (Schauss et al., 2006b), both of which have roles in acute and chronic inflammation.
Lower concentrations of the freeze-dried pulp were found to be slightly stimulating to macrophages in vitro. Macrophages are white blood cells that are an important part of the immune system of the body. Also in macrophages, freeze-dried açaí pulp was found to inhibit the production of nitric oxide that had been induced by the potent inflammatory inducer lipopolysaccharide (LPS), which is part of the cell membrane of certain bacteria (Schauss et al. 2006b). This effect increased as the concentration of the açaí increased.
In 2006, a study performed at the University of Florida showed that açaí fractions containing polyphenolics could reduce proliferation of HL-60 leukemia cells in vitro. This was most likely due to increased rapid cell death (apoptosis) as fractions were also found to activate caspase-3 (an enzyme important in apoptosis) which was inversely correlated to cell death. (Pozo-Insfran et al., 2006).
Due to its deep pigmentation, orally-administered açaí has been tested as a contrast agent for magnetic resonance imaging of the gastrointestinal system (Cordova-Fraga et al., 2004). Its anthocyanins have been characterized for stability as a natural food coloring agent (Del Pozo-Insfran et al., 2004).
