All About Acai
Acaí Palm (IPA [asai]) 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 tall, with pinnate leaves up to 3 meters long. Many of the palms that were once in the genus Euterpe have now been reclassified into the genus Prestoea (Riffle, 2003). The species Euterpe oleracea is usually called Acaí Palm, after the Portuguese name for the beverages made from its fruit. The vernacular name is also sometimes spelled Assai Palm in English.
The acai fruit, a small, round, black-purple drupe about 1 inch 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 epicarp 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 88-90% of the fruit (Schauss, 2006c).
Table Of Contents of All About Acai:
Palm hearts (the soft inner growing tip of the palm, particularly from Euterpe edulis but also from Euterpe oleracea) are consumed, often in salads. The extraction of the palm's heart involves the inevitable death of the entire palm tree, as no new branches will grow after its growing tip is removed. Given that harvesting kills the tree and is a costly and labor intensive task, palm heart dishes are regarded as a delicacy more than a staple diet; palm's heart is sometimes called "Millionaire's Salad" due to its high price. The Wall Street Journal published an article in 2002 stating that palmiteiros, or palm poachers, are illegally cutting down 5,000-10,000 palm trees per week for these hearts of palm.
An alternative to the indiscriminate harvesting of the hearts of palm is the use of the berries, which produce a crop twice per year. Utilizing the berries contributes to the local economy of the rainforest while saving the life of the trees. In a study of three traditional Caboclo populations in the Amazon region of Brazil, acai palm was described as the populations' most important plant species because the fruit makes up such a major component of their diet (up to 42% of the total food intake by weight), and is additionally economically valuable in the region (Murrieta et al., 1999). The juice and pulp of acaí fruits (Euterpe oleracea) are frequently used in various juice blends, smoothies, sodas, and other beverages. In northern Brazil, acai is traditionally served in cuias with tapioca and sometimes sugar. Acai has become a fad in southern Brazil, where it is consumed cold as acaí na tijela ("acai in the bowl"). Acaí juice and blends are no longer limited to the Amazon region, but are now a part of the worldwide market. The fruits deteriorate rapidly after harvest, so outside the tree's growing region the fruit is generally only available as juice or fruit pulp that has been frozen, dried, or freeze dried. Recently it has been shown that the high ORAC antioxidant value of the acaí fruit was greatly enhanced when a freeze-drying process was utilized to preserve the fruit pulp compared to other drying methods (Schauss, 2006c). (See antioxidant section below).
Apart from consumption, the acai palm can also be used for a number of other things. The leaves of the tree are often used in weaving hats, mats, and baskets, as well as thatched homes. The dried fruit stalks can be made into brooms, and the wood is very resistant to pests and is used in construction (Silva, 2005). The seed, which makes up 80% of the fruit, is often used for livestock food (especially for pigs) or as organic soil for plants. Seeds can also be used, of course, for sprouting new palm trees, which under the right growing conditions take only months to form seedlings, although acai palm has not been successfully cultivated outside of South America. (Schauss, 2006c) The seeds from the fruit is also used in a variety of jewelry, and is a very popular item bought by tourists and locals alike. The unripe fruit and roots have been used traditionally for gastrointestinal problems, especially as an anti-diarrheal agent. Topically the sap has been used for its astringent properties, and the tree may useful as a structural fiber source. The oil from the fruit may have industrial uses (Silva, 2005) (Plotkin, 1984). 250066530048
Several early studies done on the nutritional composition of acai were summarized by Rogez in a 2000 book in Portuguese entitled "Acaí: Prepario, Composicao e Melhoramento de Conservacao" (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 acaí fruit pulp and skin powder found nutrient analysis results from 100 g 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, acaí is an exceptional source of this valuable macronutrient. A 100 g serving of fruit pulp would provide all the recommended fiber needs for adults (30 g per day).
Acaí is particularly rich in fatty acids, feeling oily to the touch. It contains high levels of the desirable monounsaturated fatty acid, oleic acid (56.2% of total fats). It is also rich in palmitic acid (24.1% of total fats, an undesirable 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).
Preliminary analyses of acaí freeze-dried skin and pulp powder show significant richness of vitamins and minerals. Vitamins B1, B2, B3, C and E are present. Vitamin C content was measured at 17 mg per 100 g (about the same as blueberries) and vitamin E at 45 mg per 100 g, is an extraordinary content for fruits or whole foods of any kind, so is questionable. 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).
Potassium content is high in acai (932 mg per 100 grams). Other minerals isolated included sodium, magnesium, copper, zinc, phosphorus, and sulphur. 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 totaled 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 (which kills the entire tree for the top growth shoot), sawdust from the left-over trunks of the acaí 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).
The dense pigmentation of acaí has led to several experimental studies of its anthocyanins, a group of polyphenols that give the deep color to fruits and vegetables and are high in antioxidant value. A recent study using a standardized freeze-dried acaí fruit pulp and skin powder found the total anthocyanin levels to be 319 mg per 100 grams (Schauss et al., 2006a). Cyanidin 3-glucoside and cyanidin 3-rutinoside were the major anthocyanins determined in this study as well several other studies including one by Lichtenthaler in 2005.
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, totaled 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 acaí in this study, although at low levels of 1.1 microgram per gram.
A number of studies have measured the antioxidant strength of acaí. Unfortunately, the sources of acaí 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 acaí powder found that this powder showed an extremely high antioxidant effect against peroxyl radical. In fact, it had the highest total antioxidant level (1027 micromol TE/g) of any other food tested by ORAC to date. This includes a high lipophilic antioxidant content when compared to other berries. 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 acaí powder including 0.1 part per trillion (Schauss et al., 2006b). A previous report using a total oxygen scavenging capacity assay also found that acaí 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. (Lichtenthäler et al, 2005).
Interestingly, the Lichtenthäler et al. study determined that only 10% of acaí's high antioxidant effects could be explained by its anthocyanin content. Schauss et al. similarly found that that ratio of the hydrophilic ORAC levels to the total phenolics in the freeze-dried fruit was 50, which is quite a bit higher than the average fruit and vegetable ratio of 10. This suggests that either there are other unknown antioxidants present contributing to this high antioxidant activity and/or the antioxidants that acaí contains are especially strong.
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.
Although it is unknown exactly how these in vitro antioxidant levels will translate into health potentials for humans in vivo, it is likely that acai fruit imparts health benefits associated with consumption of foods high in antioxidants, such as reduced risk or prevention of chronic and oxidative stress related disorders.
Antioxidant values of the seeds of the acaí 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 the 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.
Acai, in the form of a specific freeze-dried fruit pulp, has been shown to have mild ability to inhibit cyclooxygenase enzymes COX-1 and COX-2, with more effect on COX-1 (Schauss et al., 2006b). These enzymes are important in both acute and chronic inflammation, and are targeted by many of the anti-inflammatory medications (NSAIDs). Additionally, lower concentrations (but not higher 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 acaí 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 acaí increased. This suggests again the potential for an anti-inflammatory effect of acai, although requires more research.
In 2006, a study performed at the University of Florida showed that acai 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). This is a very preliminary study, but indicates a need for more research on the possible anti-cancer effects of acaí.
Due to its deep pigmentation, orally-administered acaí 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).
Acaí has been consumed by humans for hundreds, maybe even thousands of years. Schauss et al. have conducted safety studies on a freeze-dried acai fruit pulp. It was not found to be mutagenic in the bacterial reverse mutagenicity assay (Ames test). Additionally, no adverse effects were seen at acute doses up to 2,000 mg per kilogram body weight in laboratory animals (similar to a human consumption of 140 grams at one time). (Schauss, 2006c).
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- Lichtenthaler, R., Rodrigues, R. B., Maia, J. G., Papagiannopoulos, M., Fabricius, H., & Marx, F. (2005). Total oxidant scavenging capacities of Euterpe oleracea Mart. (Acai) fruits. Int. J. Food Sci. Nutr. 56: 53-64.
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