Açaí (Euterpe oleraceae) 'BRS Pará': A tropical fruit source of antioxidant dietary fiber and high antioxidant capacity oil
ABSTRACT This article reports a study of the concentrations of dietary fiber (DF) and antioxidant capacity in fruits (pulp and oil) of a new açaí (Euterpe oleraceae) cultivar—‘BRS-Pará’, with a view to determine the possibility of using it as a source of antioxidants in functional foods or dietary supplements. Results show that ‘BRS-Pará’ açaí fruits has a high content of DF (71% dry matter) and oil (20.82%) as well as a high antioxidant capacity in both defatted matter and oil. ‘BRS-Pará’ Açaí fruits can be considered as an excellent source of antioxidant dietary fiber. Antioxidant capacity of açaí ‘BRS-Pará’ oil by DPPH assay was higher (EC50=646.3g/g DPPH) than extra virgin olive oil (EC50=2057.27g/g DPPH). These features provide açaí ‘BRS-Pará’ fruits with considerable potential for nutritional and health applications.
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ABSTRACT: In recent decades, the food industry has been meeting the growing demand of consumers in search of foods that have benefits that go beyond their nutritional value, and this sector has generated billions of dollars in the global market. Lifestyle, the convenience and speed of the preparation and the modification of eating habits among the population all reflect the increasing incidence of chronic diseases caused by eating high-calorie foods and a lack of exercise. Advances in food science knowledge have become available to demonstrate the function and mechanism of action of bioactive compounds, and they support the inclusion of ingredients and the design and development of foods that contribute to a healthy diet that is associated with a healthy lifestyle. Although functional foods should be consumed as such and not in the form of supplements or capsules, the introduction of bioactive ingredients or components into the formulation and processes of these supplements can be a tool for industry innovation and contributes to the ability to offer products with additional quality. Traditionally, dairy products were associated with health benefits, and in part, they still have this status; thus, innovations in this area are generally associated with the use of lactic acid bacteria (LAB) or products containing probiotic microorganisms or the addition of functional ingredients and bioactive metabolites. Various procedures, such as encapsulation, could be used to protect and maintain the viability of microorganisms in foods. There is atendency towards the use of cheap and sustainable new materials with properties consistent with ingredient control release. The concept of functional starter cultures that per se may not be probiotics but may improve product quality or result in physiological effects for the consumer is a possibility that should be explored. In addition to the probiotic properties, other choices include the use of in situ cultures that inhibit pathogenic contaminants by antimicrobial action; degrade or remove toxic compounds; produce vitamins or exopolysaccharides (EPSs); contribute to viscosity, body or texture; and facilitate adherence to specific sites in the host. The action of binding EPS mucoid bacteria to the protein matrix results in increased viscous behaviour, and some EPSs produced by LAB are beneficial to health due to their prebiotic and hypocholesterolemic effects, immunomodulation ability or anticancer activity. Confirming these observations, some authors reported that the production of exopolysaccharides by certain bifidobacteria can increase the viscosity of fermented foods, contributing to the rheological properties, and therefore can be considered to be natural additives preferred by consumers that can replace plant or animal stabilisers. The use of the special characteristics of LAB to potentiate their effects in foods or food supplies to vegetarians and people with dietary or religious restrictions provides an alternative to differentiated products. This category includes foods that are lactose free, have an increased fibre content, are free of animal products, and have an increased amount of antioxidant bioactive compounds (e.g., isoflavones, aglycones, oligosaccharides). Fruits and vegetables contain high levels of beneficial substances (e.g., antioxidants, vitamins, fibre and minerals), and the addition of LAB and probiotics can add more features. The knowledge of their behaviour in fruit and vegetable matrices as vehicles for the use of probiotics or bioactive ingredients is fundamental and still largely unexplored in the literature or in industrial processes. There is, however, a need for the emerging pressure or process as a whole to be consistent with sustainable practices throughout the production chain in terms of the economic, environmental or social issues. Each step of the process that adds value to a product or avoids the generation of waste or effluent will be in agreement with the goals of clean production. This chapter will focus on the recovery of by-products and innovative uses of plant materials and the strengthening of the resources for and beneficial effects of combining foods to obtain value-added functional products and offer alternatives to consumers searching for ways to improve their health through specialty foods.Food Industry, 01/2013: chapter Differentiated Foods for consumers with new demands: pages 163-190; , ISBN: 978-953-51-0911-2
Açaí (Euterpe oleraceae) ‘BRS Pará’: A tropical fruit source of antioxidant dietary fiber
and high antioxidant capacity oil
Maria do Socorro M. Rufinoa,b,1, Jara Pérez-Jiménezb,2, Sara Arranzb, Ricardo Elesbão Alvesc,⁎,
Edy S. de Britoc, Maria S.P. Oliveirad, Fulgencio Saura-Calixtob
aFederal Rural University of the Semi-Arid, BR 110, Km 47, Presidente Costa e Silva, 59625-900, Mossoró, RN, Brazil
bDepartment of Metabolism and Nutrition, Institute for Food Science and Technology and Nutrition (ICTAN-CSIC), Calle José Antonio Novais, 10, 28040 Madrid, Spain
cEmbrapa Tropical Agroindustry, R. Dra. Sara Mesquita, 2270, Pici, 60511-110, Fortaleza, CE, Brazil
dEmbrapa Western Amazonia, Trav. Dr. Enéas Pinheiro s/n°, 66095-100, Belém, PA, Brazil
a b s t r a c ta r t i c l ei n f o
Received 1 July 2010
Received in revised form 8 September 2010
Accepted 10 September 2010
Antioxidant dietary fiber
This article reports a study of the concentrations of dietary fiber (DF) and antioxidant capacity in fruits (pulp
and oil) of a new açaí (Euterpe oleraceae) cultivar—‘BRS-Pará’, with a view to determinethe possibility of using
it as a source of antioxidants in functional foods or dietary supplements. Results show that ‘BRS-Pará’ açaí
fruits has a high content of DF (71% dry matter) and oil (20.82%) as well as a high antioxidant capacity in both
defatted matter and oil. ‘BRS-Pará’ Açaí fruits can be considered as an excellent source of antioxidant dietary
fiber. Antioxidant capacity of açaí ‘BRS-Pará’ oil by DPPH assay was higher (EC50=646.3 g/g DPPH) than extra
virgin olive oil (EC50=2057.27 g/g DPPH). These features provide açaí ‘BRS-Pará’ fruits with considerable
potential for nutritional and health applications.
© 2010 Elsevier Ltd. All rights reserved.
Açaí (Euterpe oleraceae), also known as cabbage palm, is a tropical
species which bears a dark purple, berry-like fruit, clustered into
bunches. Its exportation to other non-tropical countries, to be used
mainly in fruit juices, has increased during several years.
Recently, much attention has been paid to its antioxidant capacity
and its possible role as a functional food or food ingredient (Coïsson,
Travaglia, Piana, Capasso, & Arlorio, 2005; Jensen et al., 2008; Mertens-
Talcott et al., 2008; Pozo-Insfran, Percival, & Talcott, 2006; Ribeiro et al.,
2010; Schreckinger, Lotton, Lila, & Mejia, 2010). The phytochemical and
Silveira, & Moura, 2009; Rufino et al., 2010). Anthocyanins, proantho-
cyanidins, and other flavonoids were foundto be the major phytochem-
with the antioxidant capacity of açaí pulp (Souza et al., 2009; Rufino,
Alves, Brito, Perez-Jimezes, & Saura-Calixto, 2009; Rufino, Fernandes,
fruit, it may be necessary, when determining its antioxidant capacity, to
study separately its oil and its defatted fraction to avoid interferences, as
it has been suggested for similar fruits (Arranz, Pérez-Jiménez, & Saura-
Calixto, 2008). This has not been carried out up to the moment.
Cereals are usually studied as main sources of dietary fiber (DF).
Nevertheless, it is well-known that the DF from some fruits, that
contains a higher proportion of soluble dietary fiber (SDF) and
associated bioactive compounds than cereals, has properties related
to gastrointestinal health and prevention of chronic diseases (Spiller,
2001). Antioxidant DF (ADF) is defined as a natural product that
combines the beneficial effects of DF and natural antioxidants, such as
polyphenol compounds (Saura-Calixto, 1998). On the one hand, ADF
can be used as a dietary supplement to improve gastrointestinal
health and to prevent cardiovascular diseases (Pérez-Jiménez,
Serrano, et al., 2008), and on the other as an ingredient in seafood
and meat products to prevent lipid oxidation (Sánchez-Alonso,
Jiménez-Escrig, Saura-Calixto, & Borderías, 2006).
breeding program based on phenotypic selection from its germplasm
Food Research International 44 (2011) 2100–2106
Abbreviations: ABTS, 2,2′-Azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid); ADF,
antioxidant dietary fiber; AE, antiradical efficiency (AE=1/(EC50tEC50); DF, dietary
fiber; DPPH●, 2,2-Diphenyl-1-picrylhydrazyl; EC50, concentration of antioxidant needed
to reduce the original amount of radical by 50%; EPP, extractable polyphenols; FRAP,
Ferric Reducing/Antioxidant Power; GAE, gallic acid equivalents; IDF, insoluble dietary
fiber; NSP, nonstarch polysaccharides; ORAC, Oxygen Radical Absorbance Capacity; SDF,
soluble dietary fiber; tEC50, time needed to reach the steady state to EC50 concentration;
TPTZ, 2,4,6-Tris(2-pyridyl)-s-triazine; Trolox, 6-Hydroxy-2,5,7,8-tetramethylchroman-
⁎ Corresponding author. Tel.: +55 85 3391 7202; fax: +55 85 3391 7222.
E-mail address: email@example.com (R.E. Alves).
1Current address: Food Technology Department, Federal University of Ceara, Av.
Mister Hall, 2977, Bloco 858, Pici, 60356-000, Fortaleza, CE, Brazil.
2Current address: Institute of Advanced Chemistry of Catalonia-CSIC, c/ Jordi Girona,
18-26, 08034 Barcelona, Spain.
0963-9969/$ – see front matter © 2010 Elsevier Ltd. All rights reserved.
Contents lists available at ScienceDirect
Food Research International
journal homepage: www.elsevier.com/locate/foodres
bank, Embrapa Western Amazonia (Belém, PA, Brazil) developed a
cultivar—the ‘BRS-Pará’—suitable for growing on stable land, as a result
the production system of this plant has now been modified making it
easier and more productive than the traditional system.
The aim of this work was to study the concentrations of DF and
antioxidant capacity in açaí, ‘BRS-Pará’ with a view to determining the
possibility of using it as a source of antioxidant in functional foods or
dietary supplements. Due to its high oil content, antioxidant capacity
was studied separately in the defatted pulp and in the oil, to avoid
interferences. Finally, since the association of antioxidants with DF
may produce specific physiological effects, the polyphenols and the
antioxidant capacity associated to DF were also determined.
2. Materials and methods
Pepsin (2000 FIP-U/g), glucose, inositol and N-methylimidazole
were obtained from Merck (Darmstadt, Germany). Amyloglucosidase
(14 IU/mg) was from, Roche, Manheim, Germany. Pancreatin, α-
amylase (17.5 IU/mg), 2,2′-Azino-bis(3-ethylbenzo-thiazoline-6-
sulfonic acid) (ABTS), 6-hydroxy-2,5,7,8-tetramethylchroman-2-
carboxylic acid (Trolox), catechin, gallic acid, galacturonic acid,
galactose and mannose were obtained from Sigma-Aldrich Química,
S.A. (Madrid, Spain). 2,4,6-Tris(2-pyridyl)-s-triazine (TPTZ) was from
Fluka Chemicals (Madrid, Spain). Dinitrosalicylic acid, 3,6′-dihydroxy-
spiro-[isobenzofuran-1-[3H],90[9H]-xanthen]-3-one (fluorescein) and
iron III-chlorure-6-hydrate were from Panreac, Castellar del Vallés
(Barcelona, Spain). All reagents used were of analytical grade.
Fruits of açaí ‘BRS-Pará’ were harvested at Embrapa Western
Amazonia at Belém-PA, Brazil. After harvesting, the fruits were
transported to the Postharvest Physiology and Technology Laboratory,
at Embrapa Tropical Agroindustry, Fortaleza-CE, Brazil. Two kilograms
of fruit were harvested in the second semester of 2007 at the
commercial maturity stage (completely ripe). Samples were taken
from 10 different trees and from different regions of them, to achieve a
homogeneous sample. They were processed in a domestic blender
(Walita, Brazil) to obtain a pulp and the seeds werediscarded.Pulp was
eachoneofthemwas freeze-dried(LH4500,TerroniFauvel,Brazil) and
milledtoaparticlesizeof lessthan0.5 mm inacentrifugalmill.Thefact
that these fruits were from the same genotype (clone) guaranteed a
similarity in the chemical composition of them.
Previously the samples were deffated with petroleum ether at
60 °C on a Soxhlet apparatus, using two extraction cycles of 30 min.
Figs. 1 and 2 show a scheme of the treatments performed to the
samples to determine DF and antioxidant capacity.
Determinations were performed in triplicate and reported on a dry
matter. Results are expressed as mean values±standard deviation.
2.3.1. Dietary fiber determination
The DF was measured based on the procedure described by Saura-
Calixto, Garcia-Alonso, Goñi and Bravo (2000). This method combines
enzymatic treatments and separation of digestible compounds by
the fraction of food that is not digested (Fig. 1). Total DF was calculated
as the sum of insoluble dietary fiber or IDF (constituted by nonstarch
polysaccharides orNSP, Klason lignin,resistantprotein,ash,extractable
dietary fiber or SDF (constituted by soluble nonstarch polysaccharides
or NSP and extractable polyphenols).
Samples (300 mg) were incubated with pepsin (0.2 mL of a
300 mg/mL solution in 0.08 M HCl–KCl buffer, pH 1.5, 40 °C, 1 h),
pancreatin (1 mL of a 5 mg/mL solution in 0.1 M phosphate buffer, pH
7.5, 37 °C, 6 h) and α-amylase (1 mL of a 120 mg/mL solution in 0.1 M
Tris–maleate buffer, pH 6.9, 37 °C, 16 h). Samples were centrifuged
(15 min, 3000×g) and supernatants removed. Residues were washed
twice with 5 mL of distilled water, and all supernatants were
combined. Each supernatant was incubated with 100 μL of amyloglu-
cosidase for 45 min at 60 °C before being transferred to dialysis tubes
(Soluble dietary fiber)
(Insoluble dietary fiber)
Resistant protein, ashes
Neutral sugars, uronic acids,
klason lignin, AC, HT
Neutral sugars, uronic
acids, AC, HT
Fig. 1. Flow chart showing determination of dietary fiber and associated antioxidants in açaí ‘BRS-Pará’. AC: antioxidant capacity; EPP: extractable polyphenols; HT: hydrolysable
tannins; CT: condensed tannins.
M.S.M. Rufino et al. / Food Research International 44 (2011) 2100–2106
(12,000–14,000 molecular weight cutoff, Visking dialysis tubing;
Medicell International Ltd., London, U.K.) and dialyzed against water
for 48 h at 25 °C to eliminate digestible compounds. The products of
all these treatments were therefore a residue after enzymatic
treatments, corresponding to IDF, and a supernantant of enzymatic
treatments later subjected to dialysis, corresponding to SDF.
In SDF, soluble NSP were hydrolyzed with 1 M sulfuric acid at
100 °C for 90 min and measured as the sum of neutral sugars,
determined by GC, and uronic acids, determined spectrophotometri-
cally (Scott, 1979) using galacturonic acid as standard. Regarding GC,
neutral sugars were derivatized to alditol acetates (Englyst, Wiggins &
Cummings, 1984) by a first treatment with NH4OH, octan-2-ol and
NaBH4 during 30 min at 40 °C, followed by a second treatment with
methylimidazole and acetic anhydride during 15 min and a final
addition of KOH. A Shimadzu GC-14A chromatograph (Shimadzu Co.,
Kyoto, Japan) fitted with a flame ionization detector and a SP-2330
capillary column (30 m×0.32 mm i.d., catalog no. 2-4073, Supelco,
Bellefonte, PA) were used. Analytical conditions were as follows:
column temperature, 240 °C (isothermal); injector temperature,
270 °C; detector temperature, 270 °C; carrier gas, nitrogen. Inositol
was used as internal standard. Finally, extractable polyphenols were
also determined in SDF as described in the later part—see Section
Regarding IDF, the residue was weighed to determine gravimet-
rically IDF content in the sample, and it was divided in three fractions
to analyze its different constituents. A first fraction was used to
determine insoluble NSP and Klason lignin (Southgate, 1969): after
treatment with sulphuric acid (12 M, 20 °C for 3 h; dilution to 1 M and
incubation for 2 h, 100 °C), insoluble NSP were determined as the sum
of neutral sugars and uronic acids as described above for soluble NSP,
and Klason lignin was determined gravimetrically. In the supernatant
of this treatment hydrolyzable tannins content was also determined—
as discussed after Section 22.214.171.124. A second fraction of the residue was
used to determine in it resistant protein and ash—see 2.3.3. The third
fraction was subjected to a first treatment to determine extractable
polyphenols—see Section 126.96.36.199, followed by a second treatment to
determine condensed tannins content—see Section 188.8.131.52.
2.3.2. Antioxidant capacity and phenolic compounds determination
184.108.40.206. Extraction of antioxidants. 0.5 g of either IDF of açaí (Fig. 1) or
defatted açaí pulp (Fig. 2) was placed in a capped centrifuge tube;
20 mL of acidic methanol/water (50:50, v/v; pH 2) was added and the
tube was thoroughly shaken at room temperature for 1 h. The tube
was centrifuged at 2500×g for 10 min and the supernatant recovered.
Twenty milliliters of acetone/water (70:30, v/v) were added to the
residue, and shaking and centrifugation repeated. Methanolic and
acetonic extracts were combined and used to determine
the antioxidant capacity associated with extractable antioxidants
(Figs. 1 and 2). The residues of these extractions were subjected either
to hydrolisis with H2SO4to release hydrolyzable tannins (Figs. 1 and
2) or to treatment with n-butanol/HCl/FeCl3to release anthocyanins
from proanthocyanidins or condensed tannins (Figs. 1 and 2)—see
conditions in Section 220.127.116.11. Antioxidant capacity was determined in
both hydrolyzable tannins and condensed tannins.
Total antioxidant capacity was determined directly in vegetable
oils, after diluting aliquots in ethyl acetate. To determine separately
antioxidant capacity associated to polar and apolar compounds, 5 mL
of oil were mixed with 5 mL of methanol. The mixture was vigorously
stirred for 20 min and centrifuged at 2500×g for 10 min and the
supernatant was recovered. Another 5 mL were added and the same
process was repeated. Antioxidant capacity was measured directly in
the methanolic extract (that extracts polar compounds) and in the
remaining oil (apolar fraction), after dilution with ethyl acetate
(Espín, Soler-Rivas, & Wichers, 2000).
18.104.22.168. Antioxidant capacity methods
22.214.171.124.1. DPPH•(free-radical scavenging) assay. It was used the
method described by Brand-Williams, Cuvelier, and Berset (1995),
later modified by Sánchez-Moreno, Larrauri, and Saura-Calixto
(1998), in order to determine kinetic parameters. After adjusting
the blank with methanol, 0.1 mL of the sample was mixed with 3.9 mL
of a DPPH•methanolic solution (60 μM). The absorbance at 515 nm
was measured until the reaction reached the plateau. A calibration
curve at that wavelength was made to calculate the remaining DPPH•.
The parameter EC50, which reflects 50% depletion of DPPH•, was
expressed in terms of grams of açaí equivalent per gram of DPPH•in
the reaction medium. The time taken to reach the steady state at EC50
(tEC50) and the antiradical efficiency (AE=1/EC50tEC50) were also
was produced by reacting 7 mM ABTS stock solution with 2.45 mM
potassium persulfate and allowing the mixture to stand in the dark at
room temperature for 12–16 h before use. The ABTS•+solution was
(solved in ethyl acetate)
(solved in ethyl acetate)
Fig. 2. Flow chart showing determination of antioxidant capacity of the defatted sample and oil of açaí ‘BRS-Pará’. AC: antioxidant capacity; EPP: extractable polyphenols; HT:
hydrolysable tannins; CT: condensed tannins.
M.S.M. Rufino et al. / Food Research International 44 (2011) 2100–2106
diluted with methanol to an absorbance of 0.70±0.02 at 658 nm. After
the addition of 100 μL of sample or Trolox standard to 3.9 mL of diluted
ABTS•+solution, absorbance readings were taken every 20 s, using a
Beckman DU-640 (Beckman Instruments Inc. Fullerton, CA, USA)
spectrophotometer. The reaction was monitored during 6 min. The
below the curve (0–6 min) was calculated (Re et al., 1999). Methanolic
solutions of known Trolox concentrations were used for calibration.
126.96.36.199.3. ABTS assay expressed kinetically. TheABTSradicalcationis
procedure described modified the original method so as to determine
kinetic parameters. An aliquot of the sample extract (0.1 mL) is added
to3.9 mLofABTS•+(0.044 g/L)inmethanolwhichwasprepareddaily.
Absorbances at 658 nm are measured at different time intervals on a
spectrophotometer until the reaction reaches a plateau. The ABTS•+
concentration in the reaction medium is calculated by plotting
concentration vs. absorbance. EC50, tEC50and AE are calculated as in
the DPPH assay (Pérez-Jiménez & Saura-Calixto, 2008).
188.8.131.52.4. FRAP (ferric reducing antioxidant power) assay. 900 μL of
FRAP reagent (80% acetate buffer, 10% TPTZ 10 mM and 10% iron III-
chlorure-6-hydrate 20 mM), freshly prepared and warmed at 37 °C,
was mixed with 90 μL of distilled water and either 30 μL of test sample
or standard or appropriate reagent blank. Reading at the absorption
maximum (595 nm) was taken every 15 s, using a spectrophotome-
ter. The readings at 30 min were selected for calculation of FRAP
values (Benzie & Strain, 1996; Pulido, Bravo, & Saura-Calixto, 2000).
Solutions of known Trolox concentrations were used for calibration.
184.108.40.206.5. ORAC (oxygen radical absorbance capacity) assay. Sample/
blank is mixed with PBS buffer, AAPH and fluorescein. Fluorescence
was recorded until it reached zero (excitation wavelength 493 nm,
emission wavelength 515 nm) in a fluorescence spectrophotometer
Perkin-Elmer LS 55 at 37 °C (Ou, Hampsch-Woodill, & Prior, 2001).
Results were calculated using the differences of areas under the
fluorescein decay curve between the blank and the sample and were
expressed as Trolox equivalents.
220.127.116.11. Antioxidant compounds content. The content of extractable
polyphenols (EPP) was determined in SDF, extracts of IDF (Fig. 1) and
in extracts of the defatted pulp (Fig. 2) according to the Folin–
Ciocalteu method (Singleton, Orthofer, & Lamuela-Raventós, 1999).
Test sample (0.5 mL) was mixed with 1 mL of Folin–Ciocalteu reagent
and swirled. After 3 min, 10 mL of sodium carbonate solution (75 g/L)
was added and mixed. Additional distilled water was mixed
thoroughly by inverting the tubes several times. After 1 h, the
absorbance at 750 nm was recorded. The results were expressed as
g of gallic acid equivalents (GAE)/100 g.
Proanthocyanidins (condensed tannins) not extracted by the
previous aqueous-organic procedure were measured at 555 nm after
hydrolysis with n-butanol/HCl/FeCl3(3 h, 100 °C) (Reed, McDowell,
(Fig. 1) or in the residue of the extraction of açaí defatted pulp (Fig. 2).
Results were compared with carob pod (Ceratonia siliqua L.) proantho-
cyanidin standard (Nestlé, Ltd., Vers-Chez-les Blancs, Switzerland).
Hydrolyzable tannins were measured according to a method
previously described (Hartzfeld, Forkner, Hunter, & Hagerman, 2002)
by hydrolysis with methanol and sulfuric acid for 20 h at 85 °C. They
weredeterminedin thehydrolysates of IDF(Fig. 1) andin theresidues
of the extraction of açaí defatted pulp (Fig. 2). Concentration was
estimated by the Folin–Ciocalteu method (Singleton et al., 1999) and
expressed as g GAE/100 g.
2.3.3. Proximate composition determination
Protein was determined using an automated nitrogen analyser FP-
2000®; Dumas Leco Corp. Lipids were determined using a Soxhlet
System HT extractor with petroleum ether, and fatty acid composition
by GC, after derivatization to methyl sters (Gómez-Cortés et al., 2008).
Ash content was gravimetrically determined by incinerating samples
in an electric muffle furnace at 550 °C for 16 h.
3. Results and discussion
3.1. Proximate composition
Proximate composition values are presented in Table 1. The most
significant aspect of açaí ‘BRS-Para’ is its high DF content (70% dry
matter), the bulk of it being insoluble DF. Açaí DF content, as in other
tropical fruits, is much higher than in common fruits like apples, oranges
or bananas in which it ranges from 17 to 36% (Saura-Calixto et al., 2000).
Moreover, açaí contains comparable levels of DF to other products
Rupérez, & Saura-Calixto, 1997; Pérez-Jiménez, Arranz, et al., 2008), and
higher than other tropical fruits like guava or papaya (Jiménez-Escrig,
Rincón, Pulido, & Saura-Calixto, 2001; Mahattanatawee et al., 2006).
Table 2 shows the composition of açaí ‘BRS-Pará’ DF, including
neutral sugars (determined individually), uronic acids, Klason lignin,
resistant protein, and ash. Glucose and galactose were the main
neutral sugars in SDF, while arabinose and xylose were the major
monosaccharides in IDF indicating the presence of arabinoxylans.
they are potentially fermentable by colonic microbiota. Some of the
metabolites generated during colonic fermentation of carbohydrates, as
short chain fatty acids (especially butyrate), weredescribed as beneficial
for intestinal health (Wong, Souza, Kendall, Emam, & Jenkins, 2006).
showed that this fruit is a source of fatty acids of potential nutritional
70% oleic acid on average, and more than other oil rich sources such as
soy, corn and sunflower. This is in line with results reported by other
authors on açaí from the Amazon estuary (Schauss et al., 2006).
Açaí also possesses a high phenolic content that presumably
contributes to its antioxidant capacity, as it is discussed in the later
part. Finally, the protein, soluble sugars and mineral content agreed
with other reported data (Menezes, Torres, & Srur, 2008).
3.2. Polyphenols and antioxidant capacity
The antioxidant capacity of any food sample comes from the
combined synergic action of a mixture of compounds, including
phenolics, carotenoids, vitamins C and E, etc. Except for certain fruits
such as acerola (Alves, Chitarra, & Chitarra, 1995), in which vitamin C
is one of the main component, in fruits like açaí which contain
relatively little of this vitamin, polyphenols are the main contributors
to antioxidant capacity.
Proximate composition of Açaí ‘BRS-Pará’ fruit pulp.
Soluble dietary fiber
Insoluble dietary fiber
Total dietary fiber
dm: dry matter. Moisture: 85.7%.
aMean value±standard deviation, n=3.
bDetermined as non-starchy polysaccharides+associated polyphenols.
dA fraction of them is included in dietary fiber.
M.S.M. Rufino et al. / Food Research International 44 (2011) 2100–2106
Polyphenol content determined in the pulp aqueous–organic
extracts can be seen in Table 4. The values are similar to those
reported by other authors (Schauss et al., 2006). The main phenolic
compounds reported in açaí pulp have been cyanidin 3-O-glucoside, a
cyanidin 3-O-rutinoside, homoorientin, orientin, and isovitexin
(Gallori, Bilia, Bergonzi, Barbosa, & Vincieri, 2004), and in the related
fruit jussara (Euterpe edulis) cyanidin 3-O-glucoside and cyanidin 3-
O-rutinoside (Brito et al., 2007).
Total polyphenols present in the residue of these extractions that
is, hydrolyzable and condensed tannins were determined, giving
values of 1.59 and 1.24 g/100 g dry weight, respectively, being
therefore as abundant as extractable polyphenols. Although non-
bioavailable in the small intestine, these non extractable polyphenols
reach the colon intact and there becomes fermentable substrates for
colonic bacterias. The fermentation of these compounds release
antioxidant metabolites that may improve the colonic status and
yield some absorbable metabolites (Cerdá, Periago, Espín, & Tomás-
Barberán, 2005; Gonthier et al., 2003).
The antioxidant capacity associated with these non-extractable
phenolic compounds in açaí had not been previously determined.
Regarding the oil, it was found only one reference in which the
antioxidant capacity of açaí oil was measured by ORAC assay
(Pacheco-Palencia, Mertens-Talcott, & Talcott, 2008). Therefore,
another aim of this work was to determine the total antioxidant
capacity of this fruit. In order to perform these determinations, it was
necessary to defat the açaí since its high oil content could interfere in
the measurement of this parameter (Arranz et al., 2008).
3.2.1. Antioxidant capacity of defatted pulp
Antioxidant capacity associated with phenolic compounds was
determined by FRAP, ABTS, DPPH and ORAC (Table 4)—the different
pros and cons linked to each one of the available antioxidant capacity
Jiménez, Arranz, et al., 2008). The aqueous–organic extracts obtained
from defatted açaí, showed high antioxidant capacity, mainly due to
extractable polyphenols, as well as the residues of açaí defatted pulp,
antioxidant capacity. In the case of condensed tannins, only ABTS was a
suitable procedure to determine their antioxidant capacity, since the
other methods are not suitable to be performed in the butanol media
needed the release of anthocyanins from proanthocyanidins.
Regarding kinetic measurements, extractable polyphenols were
better radical scavengers than hydrolyzable tannins when ABTS assay
was used (lower EC50), but worse radical scavengers towards DPPH
assay (EC50 of 4.92 g/g for hydrolyzable tannins vs 10.20 for
extractable polyphenols), indicating different mechanisms of reac-
tions in these two assays (Huang, Ou, & Prior, 2005). Fig. 3 shows the
kinetic behaviour of açaí extracts vs DPPH●.
3.2.2. Antioxidant capacity of the oil
Açaí ‘BRS-Pará’ oil antioxidant capacity results are shown in Table 5.
Only total oil and apolar fraction values can be directly compared, since
both were measured using ethyl acetate as solvent, while the polar
fraction measurements were performed in methanol. The EC50of the
apolar fraction (536.5 g/g) was higher than that of total oil (646.3)
indicating a higher antioxidant capacity; therefore, it seems that most
antioxidants inaçaíoil are of anapolarnature,and the extraction of this
fraction works as a mechanism to concentrate antioxidants.
We compared these values with extra virgin olive oil as a model of
a lipophilic antioxidant-rich sample (Arranz et al., 2008), since oil
extraction and antioxidantcapacity measurements were equivalentin
both studies. The EC50of total oil was lower in the açaí oil than in the
extra virgin olive oil (646.30 g/g DPPH vs. 2057.27 g/g DPPH)
indicating higher antioxidant capacity in the former. In contrast, the
antiradical efficiency (AE) of extra virgin olive oil was higher, because
the time required for açaí oil to achieve the EC50was longer than that
requiredfor theextra virginoliveoil.For theapolar fraction,againaçaí
oil had a lower EC50than olive oil (536.53 g oil/g DPPH vs. 1210.96 g
oil/g DPPH) and consequently higher antioxidant capacity to capture
DPPH radical. Açaí and olive oil apolar fractions showed similar results
for tEC50. However, regarding polar fraction, olive oil exhibited a much
higher antioxidant capacity (EC50of 10.2 g/g) than açaí oil (EC50of
Therefore, açaí oil appears as a new source of lipophilic anti-
oxidants, with an antioxidant activity similar to olive oil, known by its
high antioxidant compounds content.
Composition of dietary fiber of Açaí ‘BRS-Pará’ pulp (% dma).
Total neutral sugars
dm: dry matter.
aMean value±standard deviation, n=3. n.d. non detected.
Fatty acid composition and oil of Açaí ‘BRS-Pará’ fruit pulp.
ComponentFatty acid (g/100 g dm)Oil (%)
Cis-9, cis-12 C18:2
Cis-9, cis-12, cis-15 C18:3
dm: dry matter.
Polyphenols and antioxidant capacity in aqueous–organic extracts and its residues of
defatted Açaí ‘BRS-Pará’ fruit pulp.a
Polyphenols (mg/g dm)
FRAP (μmol Trolox/g dm)
ORAC (μmol Trolox/g dm)
ABTS at a fixed
end-point (μmol Trolox/g dm)
ABTS expressed kinetically
EC50(g dm/g ABTS)
EC50(g dm/g DPPH)
dm: dry matter. n.d. non determined. All values are expressed per gram of dry whole
aMean value±standard deviation, n=3.
bAntiradical efficiency, AE=1/(EC50tEC50).
M.S.M. Rufino et al. / Food Research International 44 (2011) 2100–2106