Constituents

 Lipids

Açai is a highly caloric food due to its high percentage of fat, which is the main component in quantitative terms (Table 1). Analysis of the total lipid content in 124 samples showed a slightly higher mean content of 52.64% of the dry matter. Due to its abundance, the lipids can easily be seen in the cut fruit by optic microscope, using a coloring of Sudan Black.  A man between 18 and 29 years of age, weighing 65 kilos, and engaged in average physical activity needs approximately 3.000 kcal/day. The daily consumption of one liter of açai with 12.5% dry matter contains 65.8g of lipids, which corresponds to 66% of the daily lipid ingestion requirement (100 g). This amount of lipids supplies 592 kcal of the total of 657 kcal contained in one liter of açai, which is  over 20% of the daily energy contribution for an adult man. This gives açai an energy value comparable to whole cow’s milk (614 kcal/l).

               Table 1

2. Profile of liposoluble components

               Table 2

Table 2 presents the complete profile of fatty acids, sterols, tocopherols, and tocotrienols in açai. According to nutritional recommendations, the ideal profile of the oil should be 50% of mono-unsaturated fatty acids, a maximum of 33% of saturated fatty acids, and the remainder should be poly-unsaturated fatty acids. Euterpe oleracea presents a particularly interesting profile from a nutritional point of view, which gives it an important advantage. However, a weak content of linolenic acid, an indispensable fatty acid is observed, and its recommendation for an adult is established at 0.5-1% of the energy (1.6 – 3.3 g/day).  On the other hand, together with this nutritional quality the high mono- and poly-unsaturated fatty acid content means that it oxidizes easily, which no doubt contributes to the drink rapidly becoming rancid.

The main sterol is beta-sitosterol and the proportions of cholesterol are small (<3.0%).  When compared to other oils, açaí had only small values of cam-pesterol.  The total amount of alfa-tocopherol presented in açaí is high (45 mg/100 g D.M.). This high vitamin E content is related to the unsaturated fatty acids present. Vitamin E (tocopherols) is an important natural anti-oxidant that protects the lipids. The daily vitamin E recommendation is 5 to 15 mg for an adult, making açaí an excellent source. 

3. Proteins

- Total nitrogenous matter

Compared to other fruits açaí has a high protein content.  The average total nitrogenous matter content found in 109 samples is 10.05% in relation to the dry matter (Table 3). One liter of açaí contains 12.6 g of proteins, which represents 25-30% of the daily required nutritional amount; this amount is not sufficient to meet the total daily nutritional requirements, especially in children and teenagers.

               Table 3

There are variations between trees, and they can be significant (p < 0.05).  Certain palm trees present an ability to synthesize more nitrogenous compounds than others under the same growing conditions. It is likely that certain açaí trees fix more nitrogen under conditions favorable to the development of the symbiotic micro-roots.


- Amino acid profile

The nutritional value of the açaí proteins were compared to egg proteins, which are a classical reference for human feeding. Two other protein sources were compared as well, partially degreased Brazilian nut flour, and palm hearts from the açaí tree. The amino acid contents found in these different foods were expressed in relative proportions for comparison reasons. The chemical index of a protein is defined by the ratio, expressed in %, between the amount of the primary limiting amino acid found in the studied food and the one found in the reference food.  The protein contents of the different food sources compared are close in terms of percentages, in relation to dry matter, even though partially degreased Brazilian nut flour is not as rich.

Looking at the amino acid profiles of the food sources compared, açaí is very similar to the egg proteins.   The primary limiting amino acid is metionine (chemical index of 60%1).  The secondary limiting amino acid is lisine and has an excess of phenylalanine and treonine.

Brazilian nut flour’s nutritional profile is less similar to the egg protein profile.  The primary, secondary, and tertiary limiting amino acids, respectively, are lisine, treonine, and isoleucine; the chemical index of the protein is 52% The Brazilian nut flour also has high levels of metionine and arginine. The profiles of the Brazilian nut flour and of açai are complementary, the excesses of the first complementing the deficits of the second.
The palm heart protein profile is less similar than any of the other food sources, mainly with regard to essential amino acids. The primary, secondary, and tertiary limiting amino acids, respectively, are metionine, isoleucine, and valine. The chemical index of the protein is very low (26%).

4. Sugars 

Açaí has an unusually high sugar content when compared to other fruits.  Saccharose (mainly present in pineapple, pears, citrus fruits, and bananas) and the monomers glucose and fructose (mainly present in kiwis, cherries, apples, plums, and grapes) are the most common forms found in açaí. These sugars come from progressive starch degradation, normally abundant before maturity.  The glycoside content (glucose, fructose, and saccharose) is relatively low (total average of 2.96% of the D.M. only) (Table 3), therefore, natural açaí can not supply energy rapidly to its consumer.

The detailed analysis of these sugars by liquid chromatography shows the presence of glucose and fructose (1.55% and 1.36% respectively in relation to the dry matter), saccharose is almost not present (0.05% of the D.M.), and starch was not detected.  One liter of açaí contains only 3.7 g of sugars (11kcal); this food can be recommended to people suffering from diabetes, to replace various fruits with higher sugar contents.
5. Fibers 

The fiber content varies widely from one fruit species to the other. In the case of açai, the total dietary fiber concentration is notably high (on average 25,22% of the dry matter) (Table 3), and makes it the second largest group of compounds present in açaí after the lipids. Part of these fibers can easily be seen with an optic microscope.

               Table 3

Fibers play a very important part in regulating the intestinal transit, as well as in participating in the prevention of colon cancer. The daily recommended intake for total dietary fibers is 35 g for adults. Consumers of açaí easily reach this amount; one liter of açaí contains 31,5 g of total dietary fibers (Table 3), which corresponds to 90% of the recommended daily intake. Açaí can be considered an excellent source of fibers.

6. Vitamins and Minerals 

The vitamin and mineral contents related in literature are present in Table 1.


- Vitamins

 In 1953 Costa showed, for the first time, the presence of vitamin B1 in açaí.  It was used to enrich the feed for pigeons that lacked the vitamin. Chaves & Pechnick (1948) mentioned the presence of beta-carotene and Costa (1959) confirmed this providing evidence for the anti- xerophthalmic factor in studies with rats Vitamin B1 (0,25 mg/100g D.M.) is often present in in oleaginous plants, however, açaí does not contain the daily recommended amount.

- Total ash

The total ash, which contains the mineral elements, presents an average concentration of 3.09% (n = 127) (Table 3). There is no evidence of mineral levels changing in the individual shoots of a tree (p‹0.05) each shoot of the tree absorbs the same amount of minerals.  The total ash contents, on the other hand, vary in a significant way throughout the course of the harvesting season (p < 0.05). An interaction exists between harvest time, and location in the levels of ash present in the tree.

Some minerals show variations in the amounts found in each shoot of the tree; these are K, B, Cu (p < 0.05), and Ca (p < 0.01).  This suggests that these variations are probably due to a genetic factor.  Shoots planted under the same conditions can concentrate certain minerals to a greater or lesser extent than others. Another possibility is that the bio-availability of the minerals in the ground changes over very small distances, even between the shoots.


- Major mineral elements

Potassium is the most abundant mineral in the açaí fruit (990 mg/100 g). High contents of this mineral in food are frequently associated with an easily growing acidity and/or with an improvement of the color; there is low sodium content (76 mg/100 g D.M.) due to the rich amounts of potassium. The magnesium found in fruits comes from the chlorophyl present before maturity, on average the content is 178 mg/100 g D.M.

Calcium is the second most abundant mineral in açaí (133 to 286mg/100g D.M. - n = 127). Calcium is associated with the cell wall structures, this may affect its bio- availability.  In the Amazon region calcium is one of the least abundant minerals.  For that reason, dairy products, which have a much higher calcium content than açaí, are consumed.
Phosphorus, is a constituint of the citoplasmatic and nuclear proteins, and plays an important part in the metabolism of carbohydrates and in energy transfer. The average amounts of this mineral in açaí are 147 mg/100 g D.M., but are not relevant compared to other fruits.

- Trace-elements

After analyzing 127 distinct samples of açaí, one liter of açaí was found to contain an average of 2.6 mg of iron (Table 1). This amount is much less that the daily required amount, and açaí can not be considered an important source of iron.
The copper content is very high for a fruit (1.38 mg/100g D.M.) and açaí can be considered an excellent source of this trace-element. The daily recommended intake of copper for adults is 1,1 mg, consumption of one liter of açaí supplies twice this amount.  The manganese content (32.3 mg/100 g D.M.) is excessive in relation to the daily required amount (10 times higher) but is not toxic.  manganese causes disorders at much higher concentrations (above 200 mg/ day) (Belitz & Grosch, 1992).  The zinc content (1,73 mg/100 g D.M.) is low for a food.  Cadmium (460 ppm of D.M.), boron (1,58 mg/ 100 g D.M.) and nickel (203 ppm of D.M.) had never been dosed before.  We would also like to mention that Almeida & Valsechi (1966) dosed aluminum and obtained a value of 2,6 mg/100 g of dry matter, normal for this kind of food.

7. Anthocyanins

The amount of anythocyanins were counted in 60 açaí fruits; the average content was 440 mg/kg of fruits. The anthocynin content per 100g of dry matter was a mean value of 1.02g, this equals around 1% of the of the dry matter.  If one liter of açaí is consumed, on average, one consumes 1.28g of the powerful antocynins.

The açaí fruits have a green color at the beginning of the ripening cycle.  During this process, pigments known as anthocyanins accumulate, causing a change in color to purple, then to violet. The anthocyanins are natural colorants, which attracts the interest of several industrial areas. Compared to other fruits, açaí is shown to be an excellent source of anthocyanins because it presents the highest concentration of this pigment in its pulp. Anthocyanins are colorants which are easily degradable through various external factors such as light, high temperatures, oxygen, etc...