M. Harmanescu, et al. Scientifical Researches. Agroalimentary Processes and
Technologies, Volume XI, No. 1 (2005), 193-198
ANTIOXIDANT CAPACITY AND COMPOSITION OF
DIFFERENT BEVERAGES, FRUIT NECTARS AND
SYNTHETIC FRUIT JUICES
Monica Harmanescu, L. Vargias, Mariana Atena Poiana, I. Gergen
Banat’s University of Agricultural Sciences and Veterinary Medicine, Faculty of
Food Processing Technology, Calea Aradului nr. 119, Timişoara, RO-300645,
România, Email: igergen@yahoo.com
Abstract
In the present study, a total of 5 fruit nectars (orange, grapefruit, pear,
apricot and peach), 2 sort of synthetic juices (lemon and orange), 5 sort of
beer and 4 sort of wine (2 white and 2 red) were analyzed for total
antioxidant capacity, vitamin C, polyphenols and mineral content. Total
antioxidant activities were analyzed using FRAP method, vitamin C
titrimetrically by indophenol dye and total polyphenols content by Folin
Ciocalteu method. The antioxidant capacities varied between 2-8 mM Fe2+/L,
total polyphenols content varied between 2-6 mM/L. The highest FRAP value
was identified for fruit nectars and red wine. The FRAP value is in good
correlation witch vitamin C and polyphenols content.
Key words: antioxidant capacities, FRAP method, total phenols and ascorbic
acid, mineral content, fruit nectars, synthetic fruit juices.
Introduction
Epidemiological studies have shown that consumption of fruit and
derived food products have health benefits against chronic diseases
including cardiovascular diseases and certain type of cancer (Doll,
1990). The health-promoting properties of fruits are due to the
presence of some vitamins (A, C, E, folates), dietary fiber and other
bioactive compounds in these food products. Among bioactive
compounds, polyphenols deserve a special mention due their free
radical scavenging activities and in vivo biological activities (Bravo,
1998). Free radicals can be generated by metabolic pathways within
body tissues; also they can be introduced by external sources, with
foods, drugs, can be caused by environmental pollution, etc. Use of
natural antioxidants, as food additives for inactivated free radicals
receives a lot of attention nowadays, not only for their scavenging
properties, but also because they are natural, non-synthetic and their
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Antioxidant Capacity and Composition of Different Beverages, Fruit Nectars and
Synthetic Fruit Juices
appreciation by consumers are very favorable (Miliauskas,
Venskutonis & van Beek, 2004).
Oxidative stress can be reduced with the provision of additional
antioxidants. Antioxidants are closely related with the prevention of
degenerative illness, such as cardiovascular, neurological diseases,
cancer and oxidative stress dysfunction (Bolck 1992, Diplock 1995).
Fruit polyphenols include a wide range of compounds with
antioxidant activity, that is, hydroxycinnamates, flavan-3-ols
(condensed tannins), gallic acids derivatives (hydrolyzable tannins),
flavonols and anthocyanins. The phenolic composition of fruits varies
greatly among cultivars and tissue. Peel tissues contain larger amounts
of phenolics, anthocyanins, and flavonols than flesh tissues (Gil,
Tomas-Barberan, Hess-Pierce & Kader, 2002). The evaluation of fruit
antioxidants capacity is not an easy task, as many methods can be used
to determine this activity, and substrates, conditions, analytical
methods, and concentrations can affect the estimated activity (Franke
& Meyer, 2000). It was used the iron-reducing capacity to evaluate the
antioxidant capacity (FRAP method) of fruit nectars and beverages
(Benzie & Strain, 1996), although we understand that these simple
method have limitation (Franke & Meyer, 2000). The aim of the
present work was to determine the phenolic, vitamin C contents plus
the total antioxidant capacity of fruit nectars and beverages (wine and
beer) commonly consumed in Romania.
Several methods are know to measure the total antioxidant capacity
(TAC) of biological samples, but we tried the FRAP assay, which
depends upon the reduction of ferric tripyridyltriazine complex to the
ferrous tripyridyltriazine by a reductant at low pH. This ferrous
tripyridyltriazine complex has an intensive blue color and can be
monitored at 593 nm (Benzie & Strain, 1996). This method was
elaborated for human plasma but many authors used these method for
aqueous or hydroalcoholic extracts of medicinal plants (Szőllősi &
Szőllősi Varga, 2002), fruits (Gil, Tomas-Barberan, Hess-Pierce &
Kader, 2002) and fruit nectars (Tosun & Ustun, 2003).
Experimental
Reagents and equipment: All chemicals and reagents were
analytical grade or purest quality purchased from Sigma, Merck,
194
M. Harmanescu, et al. Scientifical Researches. Agroalimentary Processes and
Technologies, Volume XI, No. 1 (2005), 193-198
Aldrich and Fluka; deionized water was used. Absorption
determination for FRAP and total phenol content was made using
SmartSpec spectrophotometer by Bio-Rad; Na+, K+, was determined
using FLAPHO flamphotometer by Carl Zeiss-Jena in air-butane
flame; Ca2+ and Mg2+ by flame absorption spectrometry using AAS1equipment by Carl-Zeiss, Jena in air-acetylene flame.
Nectars, juice and beverages: In the present study, a total of 5 fruit
nectars (orange, grapefruit, pear, apricot and peach), 2 sorts of
synthetic juices (lemon and orange), 5 sort of beer and 4 sort of wine
(2 white and 2 red) were analyzed. Fruit nectars, synthetic juices, beer
and wine, each processed by 3 different firms were purchased from
local supermarkets.
Evaluation of total antioxidant capacity (TAC) (adaptation of
FRAP method). Reagents: acetate buffer, 300mM/L, pH 3.6 (3.1g
sodium acetate 3H2O and 16 mL conc. Acetic acid per 1L of buffer
solution); 10mM/L TPTZ (2,4,6-tripyridyl-s-triazine) in 40 mM/L
HCl; 20mM/L FeCl36H2O in distilled water. FRAP working solution:
25mL acetate buffer, 2.5mL TPTZ solution and 2.5 mL FeCl 3 solution.
The working solution must be always freshly prepared. Aqueous
solution of known Fe(II) concentration was used for calibration, in a
range of 0.1-1.0 mM/L. For the preparation of calibration curve 1ml
aliquot of 0.1, 0.2, 0.4, 0.6, 0.8, 1.0 M/mL aqueous Fe(II) as Mohr
salts solution were mixed with 5 ml FRAP working solution; FRAP
reagent was used as blank. The absorption was read after 10 min. at 25
°C at 593 nm, 1cm lights path, and the calibration curve was drawn.
One mL from diluted 1/10 nectars, juice, beer and wine was mixed
with the same reagents as described above, and after 10 min. the
absorption was measured. All determinations were performed in
triplicate. Total antioxidant capacity in plant methanol extracts in
Fe(II) equivalents was calculated. Correlation coefficient (r2) for
calibration curve was 0.859.
The amount of phenolic compounds: The following reagents were
used: 2.0M Folin-Ciocalteu phenol reagent, gallic acid and anhydrous
carbonate. The content of total phenolic compounds in plant
methanolic extracts was determined by Folin-Ciocalteu method (1927).
For the preparation of calibration curve 1ml aliquot of 0.16, 0.32, 0.60,
1.20, 2.0, 2.8 M/mL aqueous gallic acid solutions were mixed with
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Antioxidant Capacity and Composition of Different Beverages, Fruit Nectars and
Synthetic Fruit Juices
10 ml Folin-Ciocalteu reagent (diluted ten-fold) and 9 mL (7.5%)
sodium carbonate. The absorption was read after 2 h at 20 °C at 750
nm and the calibration curve was drawn. One mL from diluted 1/10
nectars, juice, beer and wine was mixed with the same reagents as
described above, and after 2 h the absorption was measured for the
determination of plant phenolics. All determinations were performed in
triplicate. Total content of phenolic compounds in plant methanol
extracts in gallic acid equivalents (GAE) was calculated. Correlation
coefficient (r2) for calibration curve was 0.875.
The amount of ascorbic acid (C vitamin): Ascorbic acid contents
were estimated titrimetrically by 2,6-dichlorophenol indophenol dye
reactant. 5 mL of nectar or beverage was diluted with 10 mL water,
adds 1mL HCl 1N, and titrates with 1mM solution of 2,6dichlorophenol indophenol dye reactant to pink color.
The amount of Na+, K+, Ca2+ and Mg2+: Na+, K+, was determined
using FLAPHO flamphotometer by Carl Zeiss-Jena in air-butane
flame; Ca2+ and Mg2+ by flame absorption spectrometry using AAS1equipment by Carl-Zeiss, Jena in air-acetylene flame. Na+ and Ca2+
were determinate directly from solutions, K+ by dilution 1/100 and
Mg2+ by dilution 1/10. Correlation coefficient (r2) for calibration curve
was 0.989 for sodium, 0.995 for potassium, 0.981 for calcium and
0.980 for magnesium.
Results and Discussions
The content of principal mineral nutrients (Na, K, Mg) from
nectars, juice, beer and wine are presented in Table 1.
The highest content of Na is present in synthetic juice, followed by
nectars and beverages. K is the major element present in nectars,
followed by wine, beer and synthetic juice. In beverages (wine, beer)
Mg is the major elements followed by nectars and at lest, synthetic
juice.
The total antioxidant capacity (TAC) by FRAP method, Vitamin C
(ascorbic acid) and polyphenols contents for analyzed products are
presented in Table 2.
The highest TAC was identified to nectars and red wine, followed
by beer, white wine and at lest, synthetic juice. The same variation
was observed for polyphenols, ascorbic acid content is higher in
196
M. Harmanescu, et al. Scientifical Researches. Agroalimentary Processes and
Technologies, Volume XI, No. 1 (2005), 193-198
nectars followed by synthetic juice and beverages. Gil, TomasBarberan, Hess-Pierce & Kader, 2002 and Tosun & Ustun 2003
reported the same results. In synthetic juice and beverages, ascorbic
acid is added like additives.
Table 1. Mineral contents of nectars, juice, beer and wine
Products
mg/L
K
840
1020
1440
840
560
9
8
252
228
344
Na
61
42
58
67
49
75
82
16
15
8
Orange
Grapefruit
Apricot
Peach
Pear
Lemon juice (synthetic)
Orange juice (synthetic)
Beer
White wine
Red wine
Mg
48
34
44
34
40
4
4
54
80
90
Table 2. Antioxidant capacity, Vitamin C and polyphenols content of
nectars, juice, beer and wine
Products
Orange (100%)
Grapefruit (100%)
Apricot (50%)
Peach (50%)
Pear (50%)
Lemon juice
Orange juice
Beer
White wine
Red wine
mM/L
Ascorbic acid
0.81
1.38
1.22
0.58
0.54
0.15
0.15
0.10
0.05
0.05
FRAP
3.80
4.40
4.80
3.40
4.10
2.80
1.40
1.83
1.80
4.80
Polyphenols
3.72
3.75
4.40
3.91
4.40
0.0
0.0
2.0
2.11
4.52
Conclusions
Nectars and red wine were the strongest TAC in FRAP assays
among the products screened. TAC is very good correlated with
polyphenols and ascorbic acid content. The highest mineral content,
especially for K and Mg which are benefic minerals, was also
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Antioxidant Capacity and Composition of Different Beverages, Fruit Nectars and
Synthetic Fruit Juices
identified in nectars and beverages but in synthetic juice was identified
high content of Na. The results of this investigation show that, being
more readily digestible than the other plant tissue fruits nectars and
also beverages, are good source of antioxidants, polyphenols, ascorbic
acid and benefic minerals. On the other parts, synthetic juice are poor
in benefic minerals, but high in Na (risk factor for high blood
pressure), poor in TAC, polyphenols and ascorbic acid which is added
as preservatives
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