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Phenolic compounds and antioxidant activity of peanut's skin, hull, raw kernel and roasted kernel flour


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In this study, phenolic compounds and antioxidant properties of peanut's skin, hull, raw kernel and roasted kernel flour (RKF) were evaluated. Total phenolic contents (TPC) and individual phenolic compounds were determined using Folin-Ciocalteau and high performance liquid chromatographic methods, respectively. Antioxidant activity was measured utilizing 2, 2-diphenyl-1-1 picrylhydrazyl (DPPH) radical scavenging capacity and inhibition of linoleic acid peroxidation assays. Results of the study showed that antioxidant activity and phenolic compounds of peanut skin were highest followed by that of peanut hull, roasted kernel flour (RKF) and raw kernel. Roasting of peanut kernels at 160°C for 10 min did not affect the overall antioxidant activity and phenolic compounds of RKF. In the present work, a good correlation was recorded between TPC and radical scavenging capacity (r 2 = 0.8436) as well as TPC versus % inhibition of linoleic acid peroxidation (r 2 = 0.6535).
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Effects of roasting on phenolics composition and antioxidant
activity of peanut (Arachis hypogaea L.) kernel flour
Mar Mar Win Azizah Abdul-Hamid
Badlishah Sham Baharin Farooq Anwar
Nazamid Saari
Received: 4 January 2011 / Revised: 13 July 2011 / Accepted: 16 July 2011 / Published online: 9 August 2011
ÓSpringer-Verlag 2011
Abstract The effects of roasting on the phenolics com-
position and antioxidant activity of peanut (Arachis hypo-
gaea L.) kernel flour were appraised. Peanut kernel flour,
with and without skin, were roasted at 160 °C for 10, 20,
30, 40 and 50 min. The resultant changes in the antioxidant
activity of roasted peanut kernel flour were assessed by the
determinations of total phenolics, 1,1-diphenyl-2-picryl-
hydrazyl free radical-scavenging capacity, percent inhibi-
tion of linoleic acid oxidation and thiobarbituric acid test
and compared with those of unroasted kernel flour. It was
observed that roasting significantly (p\0.05) increased
the antioxidant activity of the peanut kernel flour. HPLC
analysis revealed the detection of three phenolic acids
(p-hydroxybenzoic, chlorogenic, p-coumaric), two flavo-
nols (quercetin, kaempferol), and a stilbene (resveratrol)
both in the roasted and unroasted samples. In peanut kernel
flour without skin, the contents of the phenolics increased
in the initial roasting phase, however, decreased gradually
in the later phase ([20 min of roasting time). In contrast,
over the course of heating, the amounts of phenolics were
noted to be slightly increased in the peanut kernel flour
with skin; the most significant (p\0.05) increase occurred
in the concentration of p-coumaric acid and quercetin at 30,
40, and 50 min of roasting. The results of this study reveal
that optimum roasting time should be sought to enhancing
the antioxidant capacity and phenolics concentration in
peanut kernel flour.
Keywords Peanut kernel Roasting time TPC
Colorimetric antioxidant assays Phenolics acids
Peanut (Arachis hypogaea L.) is one of the major oilseed
crops cultivated in many regions across the world. It is
valued as an important food protein source in the devel-
oping and developed countries. Peanuts are not only used
as a source of edible oil but are also consumed directly or
incorporated into different foods such as snacks and con-
fectionary products for nutrition purposes. Epidemiological
studies suggest that consumption of peanut and peanut
based-products can protect against the incidence of coro-
nary heart diseases (CHD) by decreasing low-density
lipoprotein (LDL) cholesterol and reducing the risk of
development of type II diabetes as well as controlling
weight gain [1,2]. Nearly, 80% of the fat in peanut is in the
form of monounsaturates (oleic acid) that may help to
lowering LDL cholesterol level in blood. Oleic acid may
also play a key role in food-derived hormonal interaction in
the intestine, which boosts satiety between meals by
M. M. Win A. Abdul-Hamid (&)B. S. Baharin
F. Anwar N. Saari
Department of Food Science, Faculty of Food Science
and Technology, Universiti Putra Malaysia,
UPM 43400, Serdang, Selangor, Malaysia
M. M. Win
B. S. Baharin
F. Anwar
N. Saari
F. Anwar
Department of Chemistry and Biochemistry, University of
Agriculture Faisalabad, Faisalabad 38040, Pakistan
Eur Food Res Technol (2011) 233:599–608
DOI 10.1007/s00217-011-1544-3
prolonging the feeling of fullness, therefore, contributing to
weight management [3,4].
Peanut kernels are typically considered as a good source
of antioxidant components and phytosterols and contain
about 50% lipid, 25% protein, and 16% carbohydrate
making them a nutritious alternative to meat products. A
number of phenolics such as hydroxybenzoic acid, ferulic
acid, coumaric acid, resveratrol, flavonoids (catechin and
procyanidins), and flavonols (quercetin and kaempferol)
have been identified in peanuts kernels along with con-
siderable amount of total tocopherols (80–140 mg/kg). In
addition to its desirable fatty acids profile, the purported
health benefits associated with consumption of peanut
kernel are mainly attributed to these bioactive compounds
[5,6]. A dry powder (peanut flour), obtained after partial
extraction of oil, from the roasted peanut kernel, is com-
mercially used as additive to increase the protein content of
various food commodities including baked goods, sauces,
dressing, etc. Some recent studies also report the rheolog-
ical, foaming, emulsifying, and water holding properties of
peanut flour [7,8]. Peanut skin (testa or seed coat),
although a potential source of plophenols, especially pro-
anthocyanidins and condensed tannins, is sometime con-
sumed along with the peanut-derived foods; however, it is
mostly discarded as an agro-waste during peanut process-
ing [9,10].
Roasting is an important step in peanut processing
industry as it is used to enhance the flavor, color, texture,
and overall palatability of the end-user products. Mature
peanut kernels are commonly dry roasted at 160 °C for
20–30 min to prepare roasted, salted peanuts [11]. How-
ever, actual roasting intensities may depend upon the
required characteristic, flavor, and applications. During the
process of roasting, some chemical changes may occur in
which sugars can condense with free amino acids, peptides,
or proteins leading to the formation of brown Maillard
reaction products with potential antioxidant activity [12].
In addition to free forms, plants also contain considerable
amounts of bound form antioxidant phenolics, it is there-
fore perceived that some processing methods might be
employed to break these covalently bounded polymeric
compounds to liberate into free forms so as to enhancing
their antioxidant capacity [13]. For instance, previously, it
has been reported that heat treatment liberated the low-
molecular weight compounds into their free forms and
hence increased the antioxidant capacity of peanut skin,
hulls, and kernels [10,14,15].
As far as we know, there have been no earlier reports yet
available studying the influence of roasting times on the
phenolics composition and antioxidant activity of peanut
kernel flour, with and without skin. Such investigations are
important to devise an optimum roasting time offering
peanut products with better antioxidant attributes. The main
objective of this research, therefore, was to elucidate the
effect of different roasting times on the phenolics compo-
sition and antioxidant attributes of two different forms of
peanut kernel flour (with and without skin) leading to
exploring their potential uses for functional foods.
Materials and methods
Trifluoroacetic acid (TFA), standards of phenolic acids
(p-hydroxybenzoic acid, chlorogenic acid, p-coumaric
acid, ferulic acid, and gallic acid), flavonoids (epicatechin,
dihydroquercetin, luteolin, and kaempferol) stilbene (trans-
resveratrol), butylated hydroxyanisole (BHA), and
a-Tocopherol, 2,2-Diphenyl-1-picryhydrzyl radical (DPPH)
were from Sigma Chemical Company (St. Louis, MO, USA)
and ferrous chloride, 2,4,6-tripyridyl-s-triazine, linoleic acid,
thiobarbituric acid, ferric chloride, and tween 20 were
obtained from Fisher Scientific (Ottawa, ON, Canada). All
other reagents used were of analytical grade from Fisher
Sample preparation and roasting
Raw, peanut pods (Virginia spreading type variety) were
obtained from an Agricultural Farm in Nay-Pyi-Taw
Township, Myanmar. Three different peanut raw samples,
harvested from different agriculture plots, were assayed.
The selection of the present peanut variety was based upon
its high yield and productivity and popularity among local
consumers. The pods (3 kg) were manually dehulled and
the kernels recovered roasted in an electric oven (Memm-
ert, UL40, Germany) equipped with an air circulation
system. The roasting temperature was set at 160 °C fol-
lowing the method of Damame et al. [11] and maintained
for 2 h to reach equilibrium before used. The roasting times
were increased gradually from 10 to 20, 30, 40, and
50 min. After cooling to room temperature, the skin was
removed from an appropriate amount/batch of the kernels,
producing kernels with and without skin. Triplicate treat-
ments were applied for roasting process. The roasted pea-
nut kernels with and without skin were ground separately
using a commercial grinder (Pensonic, Malaysia) and then
sieved to get fine power (peanut flour). Peanut flour (10 g)
was defatted with n-hexane (100 mL) using a water bath
shaker for 8 h at 45 °C. After that, the defatted samples
were ambient dried, packed in amber bottles, and preserved
at -20 °C until used for antioxidants extraction and HPLC
analysis. Control samples (unroasted samples) of peanut
flour with and without skins were also defatted and kept at
the same conditions.
600 Eur Food Res Technol (2011) 233:599–608
Extraction of antioxidant components
Extraction of antioxidant components was carried out
according to method of Chukwumah et al. [16] with slight
modifications. Each of the defatted ground kernel sample
(10 g) was extracted with pure methanol (100 mL) using a
water bath shaker for 2 h at room temperature (28 °C). The
suspension was filtered through a Whatman No. 1 filter
paper, and the residue obtained was re-extracted twice,
with additional 100 mL of methanol. The filtrates were
pooled and the solvent distilled off under reduced pressure
using a rotary evaporator at 40 °C. The crude concentrated
extracts were used for the following antioxidant activity-
related experiments.
Total phenolic contents
The amounts of total phenolics in the roasted and unroasted
peanut kernel flour with and without skin were determined
using Folin–Ciocalteau procedure as described by [17].
Methanol extract (0.4 mL) of each sample (1 mg/mL
concentration) was mixed with 2 mL of the Folin–Ciocal-
teau reagent. After 5 min, 1.6 mL of sodium carbonate
solution (75%) was added to maintain basic condition for
the reaction to occur between phenolic components and
Foiln reagent. The reaction mixture was mixed well using
vortex machine and then incubated for 30 min at room
temperature (28 ±1°C) in the darkness. The absorbance
of the reaction mixture was then noted at 750 nm using a
UV–visible spectrophotometer (Shimadzu, Japan). The
standard calibration curve was prepared using gallic acid
standard solutions of known concentrations (0.02, 0.04,
0.06, 0.08, 0.10, and 0.20 mg/mL), and the amounts of
total phenolics were calculated as gallic acid equivalent
mg/g of dry sample (mg GAE/g dry sample).
Free radical-scavenging capacity (DPPH)
Antioxidant activity of methanol extracts from roasted and
unroasted peanut kernel flour samples was measured using
2,2-diphenyl-1-picrylhdrazyl (DPPH) according to the
method as described by Brand-Willian et al. [18], with
minor modifications. The extracts (0.5 mL) of varying
concentration were mixed with 2.5 mL of freshly prepared
DPPH solution (25 mg/L). The solution was then incubated
in the darkness at room temperature for 30 min, and the
decrease in absorbance was noted at 515 nm using a UV–
visible Spectrophotometer (Shimadzu, Japan). For blank,
pure methanol was used in place of the sample. For posi-
tive controls, 0.1 mg/mL of each a-tocopherol and BHA
(reference antioxidants) were employed. The percent
DPPH free radical scavenged by each sample extract was
calculated by the following equation:
absorbance of DPPH solution without sample/standard
solution, and A
absorbance of the sample/standard solu-
tion at 30 min reaction.
Inhibition of linoleic acid peroxidation
Methanol extracts of roasted and unroasted peanut kernel
flour were tested for their antioxidant activity by measuring
the inhibition of linoleic acid peroxidation following a
previously reported method of Yen and Hsieh [19]. Test
sample 0.5 mL (1 mg/mL in absolute ethanol) was mixed
with 2.5 mL of linoleic acid emulsion (0.02 M, pH 7.0) in
phosphate buffer. This emulsion was prepared by mixing
and homogenizing 0.280 g of linoleic acid, 0.280 g of
tween 20 as emulsifier, and 50 mL of phosphate buffer
solution. The resulting reaction mixture was subjected to
incubation at 37 °C for 96 h. The magnitude of linoleic
acid oxidation was determined by the peroxide value fol-
lowing a colorimetric method as described by Yen et al.
[20]. Briefly, to 0.1 mL sample solution, 4.7 mL of ethanol
(75%), 0.1 mL of ammonium thiocyanate (30%), and fer-
rous chloride (0.1 mL, 0.02 M in 3.5% HCl) were added
sequentially. After 3 min of reaction, the absorbance of the
resulting reaction mixture was read at 500 nm using a
spectrophotometer (Shimadzu, Japan). The degree of oxi-
dation was measured after every 24 h until a day after the
absorbance of the control reached its maximum. A control
contained all reagents without the sample extract was
prepared simultaneously. Besides, BHA, a-tocopherol, and
quercetin were used as positive controls (1 mg/mL each
compound). The percent inhibition of linoleic acid oxida-
tion was calculated as the following equation:
Inhibition of linoleic acid oxidation %ðÞ¼
1Absorbance at 500 nm in the presence of sample 96 h
Absorbance at 500 nm in the absence of sample 96 h
Thiobarbituric acid method
The antioxidant activity of the extracts from roasted and
unroasted peanut kernel flour was also measured using thio-
barbituric acid (TBA) method as described by Ottolenghi [21]
and Kikuzakiand Nakatani [22]. The same reaction mixture as
employed for measurement of percent inhibition of linoleic
acid oxidation test at the final day of the experiment was used
for TBA test. Briefly, to 1 mL of assay mixture, 2 mL of 20%
trichloroacetic acid (TCA) solution and 2 mL of TBA solution
were added. The reaction mixture was then incubated in a
boiling water bath for 10 min. After cooling to room
Eur Food Res Technol (2011) 233:599–608 601
temperature, the solution was centrifuged at 9009gfor
20 min, and the absorbance of the supernatant was measured
at 532 nm using a spectrophotometer (Shimadzu, Japan).
HPLC analysis of phenolic compounds
The analysis of selected phenolic acids (p-hydroxybenzoic,
caffeic, chlorogenic, p-coumaric, and ferulic), flavonoids
(epicatechin, quercetin, kaempferol, and luteolin), and
stilbene (trans-resveratrol) was based on the fact they are
commonly found in peanuts. The analysis was performed
by HPLC on the acid-hydrolyzed samples according to the
method as described by Wang et al. [23], with slight
modifications. Briefly, roasted and unroasted kernel flour
(0.5 g) was mixed with 10 mL of 80% methanol and 1 mL
of 1.2 M hydrochloric acid and hydrolyzed by incubation
in a water bath at 80 °C for 2 h. After hydrolysis, it was
cooled at room temperature and centrifuged at 1,2009gfor
5 min. The supernatant was filtered using a 0.45 lm nylon
membrane filter, prior to an HPLC analysis.
A Waters HPLC system equipped with Waters 2487 Dual
Wavelength Absorbance Detector, Waters 600 Pump and
controlled by Waters Empower2 software (Waters, Milford,
MA) was used. The separation of the phenolics was carried
out on Waters reverse-phase (RP) Symmetry C
(150 93.9 mm, 5 lm) operated at room temperature. The
mobile phase consisted of TFA in deionized water (pH 2.5)
as solvent A and absolute methanol (99.99%) as solvent B.
The gradient conditions used were as follows: 100–50%
solvent A (0–20 min), 50–40% solvent A (20–30 min), and
40–100% solvent A (30–40 min). The mobile phase flow
rate was set at 1.0 mL/min, and a 20 lL sample volume was
injected. The detection of the phenolic was monitored at
280 nm because this wavelength is near the maximum
absorbance wavelength for hydroxybenzoic acids
(270–280 nm), hydroxycinnamic acids (290–300 nm), and
some flavonoids (250–270 nm, 330–350 nm) [24]. The
phenolic standard solutions were prepared by dissolving
respective pure compounds in absolute methanol at various
concentrations (0.005, 0.01, 0.02, 0.05, 0.1, and 0.2 mg/mL)
and injected into the HPLC system to construct the cali-
bration curves for each standard compound. Identification of
the unknown phenolics was based on matching their reten-
tion times with those of pure standards of phenolics. Peak
areas, based on external standard calibration curves, were
used for quantification purposes. The amounts were
expressed as lg/g defatted sample.
Statistical analysis
Three different peanut samples were analyzed individually
in triplicate. All experiments were performed in triplicates.
The data were expressed as means ±standard deviations
of triplicate determinations (n=393). One-way analysis
of variance (ANOVA) and Duncan’s multiple range test
(DMRT) were carried out to assess the significance of the
differences between means (p\0.05) using SAS System
for Windows Version 7 (SAS Institute Inc., Cary, NC,
Results and discussions
Total phenolic contents
It is well known that there is a positive association between
consumption of plant foods rich in phenolic antioxidants
and health. Thermal processing is reported to significantly
alter the phytochemical and functional composition in
legumes including peanuts [16,25]. Chukwumah et al. [16]
investigated the effects of different processing techniques
such as boiling, oil-, and dry-roasting on the phenolics
composition and antioxidant activity of peanuts. In the
present study, we investigated the effects of different
roasting times on the total phenolic contents (TPC) of
peanut kernel flour with and without skin. Results of the
study showed that TPC of peanut kernel flour with and
without skin increased significantly (p\0.05) as function
of roasting times (Fig. 1). The amount of TP in the roasted
peanut kernel without skin significantly (p\0.05)
increased from 0.94 mg GAE/g in unroasted control to
1.61, 1.83, 2.16, and 2.04 mg GAE/g in the samples
roasted for 20, 30, 40, and 50 min at 160 °C, respectively.
However, TPC of roasted sample without skin were almost
unaffected during the initial stage (10 min) of roasting. In
agreement with our present finding, some previous studies
also revealed that initial stage of heating or roasting
Fig. 1 Effect of roasting times on total phenolic contents (TPC)of
peanut kernel flour with and without skin. Values with same small
letters (a,b,c) are not significantly different (p\0.05), among
different roasting times. Values with same capital letters (A,B) are not
significantly different (p\0.05) between the samples
602 Eur Food Res Technol (2011) 233:599–608
process did not exert significant effect on the TPC of
buckwheat and apricot kernel [26,27].
For peanut kernel flour with skin, TPC increased sig-
nificantly (p\0.05) as roasting times increased and
maximum values, 4.08 and 3.86 mg GAE/g, were obtained
for 40 and 50 min roasted samples, respectively. It can be
seen that peanut kernel flour with skin contained signifi-
cantly higher amount of total phenolics than peanut flour
without skin. A higher phenolic content in peanut kernel
flour with skin might be ascribed to the presence of certain
phenolics such as proanthocyanidins (condensed tannins)
in the skin. According to Karcheshy and Hemingway [28],
peanut skin was found to be a rich source of proanthocy-
anidins that contributed 17% by weight of the skin. Of the
identified proanthocyanidins, about 50% were low-molec-
ular weight oligomers [28].
It can be expected that bound form phenolics with larger
molecular weight, both in peanut kernel flour with and
without skin, might have been liberated into simple free
forms by heat treatment leading to enhancing over all TPC
of the samples. Several studies reported that heat treatment
is effective toward increasing the total phenolic content in
different foods such as dry beans [29], carob powder [30],
vegetables [31], and grape seeds [32]. Boateng et al. [29]
explained that disruption of the cell wall through heating or
by the breakdown of insoluble phenolic compounds as
function of thermal treatments could lead to better
extractability of phenolic compounds in dry beans. How-
ever, Lee et al. [14] revealed that simple heat treatment did
not liberate covalently bound phenolic compounds from
rice hull while far-infrared treatment broke the esterified
phenolic bonds. This indicates that an effective processing
method for liberation of such bound plant phenolics into
simpler forms may differ from species to species [33]. In
addition, the increase in total phenolics of peanut kernel
flour in this study may also be linked to the development of
Maillard reaction products that are reported to be formed
during roasting process. Yu et al. [10] investigated that
Maillard reaction products might lead to increase the
amounts of total phenolics or phenolic-like complexes that
further contribute to higher absorbance readings measured
by Folin assay.
DPPH free radical-scavenging activity
The antioxidant activity of methanol extracts from roasted
peanut kernel flour with and without skin, supported with
two positive controls, i.e., BHA and a-tocopherol, was
determined by measuring their DPPH
capacity (Fig. 2). DPPH is a stable free radical that has
ability to accept an electron or hydrogen from antioxidant
compounds and is then converted to a DPPH stable mol-
ecule. The loss of DPPH radical is examined by the
decrease in the magnitude of absorbance of the antioxidant
solution at 515 nm. In the present experiment, DPPH free
radical-scavenging activity of the extracts from peanut
kernel flour without skin linearly increased as function of
roasting times. The extracts, from 20, 30, 40, and 50-min
roasted samples of peanut flour without skin, showed sig-
nificantly (p\0.05) higher DPPH radical-scavenging
activity (68.93, 71.70, 77.26, and 79.57%, respectively)
than 10-min roasted (51.22%) and unroasted samples
(48.09%). The roasting time was found to be a critical
factor to determine the overall antioxidant activity of the
peanut kernel flour without skin. The highest antioxidant
activity, in terms of DPPH free radical-scavenging capac-
ity, was exhibited between 20 and 50 min of roasting. On
the other hand, the peanut kernel flour with skin, when
roasted for 10–50 min, also showed good scavenging
activity (86.96–88.61%), relative to that of unroasted
sample (75.15%). The present scavenging ability values of
roasted kernel flour with skin were comparable to that of
positive control a-tocopherol (89.00%).
The potential health benefits of plant phenolics are
mainly due to their free radical-scavenging activities
through donating a hydrogen atom and or an electron from
an aromatic hydroxyl group to free radicals [34]. In the
present study, an enhancement in the radical-scavenging
activity, observed in both the roasted peanut kernel flour
with and without skin, might be attributed to their better
ability to release some bound antioxidant phenolic com-
pounds to act as free radical scavengers, from the cell
matrix upon roasting [35]. On the other hand, other phe-
nomenon may also involve, for example, better solubility
of non-phenolic compounds (such as Maillard reaction
products) following the thermal treatments, which may
further enhance the free radical-scavenging properties of
processed foods [35,36]. Jeong et al. [37] also investigated
Fig. 2 Effect of roasting times on DPPH radical-scavenging activity
of peanut kernel flour with and without skin. Values with same small
letters (a,b,c) are not significantly different (p\0.05), among
different roasting times. Values with same capital letters (A,B) are not
significantly different (p\0.05) between the samples
Eur Food Res Technol (2011) 233:599–608 603
that roasting increased the radical-scavenging activity of
sesame meal extracts and a positive linear correlation
between melanoidin content and antioxidant activity of the
roasted coffee brew fractions was established [38]. In our
study, the increase in the radical-scavenging activity of
peanut kernel flour, in relation to increasing roasting times,
is in good agreement with the previous studies on apricot
kernels [27] and okra seed flour [39].
Antioxidant activity in linoleic acid peroxidation
The effects of roasting treatments on antioxidant activity of
peanut kernel flour were also assessed by measuring per-
cent inhibition of linoleic acid oxidation using a colori-
metric method (Fig. 3). The peroxyl radicals, formed in the
initiation step of oxidation as result of abstraction of
hydrogen from a fatty acid and subsequent oxygen
involvement, are good oxidizing agents. These peroxyl
radicals oxidize ferric thiocyanate to ferrous thiocyanate
yielding a colored complex, the intensity of which is
measured at 500 nm and can be used as a basis for the
measurement of peroxide level formed during the initial
stage of lipid oxidation [40]. At a concentration of 500 lg
in the final reaction mixture, the extracts from samples of
roasted peanut kernel flour with skin inhibited
63.03–69.33% peroxidation of linoleic acid as against
26.86–56.29% for peanut kernel flour without skin,
wherein, the roasting effects were followed in a time-
dependent manner.
Interestingly, both raw (unroasted) and roasted peanut
kernel flour with skin exhibited higher lipid peroxidation
inhibition activity (65.91 and 63.03–69.33%, respectively),
almost comparable to those of quercetin (65.71%), and
tocopherol (73.05%) but lower than that of BHA (89.30%).
An increase in the peroxidation inhibition magnitude of the
extracts, from peanut kernel flour with skin, might be due
to higher amounts of polyphenols present in peanut skin
that contributed to inhibit the accumulation of oxidative
products. Generally, it is believed that outer layers of seed
such as peel, shell, and hull contain higher amounts of
polyphenolic compounds to protect the seed from oxidative
damage [41]. Similarly, as our present findings, the seed
coat extracts of red and black bean, containing higher
amount of phenolic substances, exhibited a stronger anti-
oxidant activity against lipid peroxidation [42]. Nonethe-
less, the stability of antioxidants of roasted samples might
be due to the formation of Maillard reaction products.
During heat treatment, the formation of the Maillard
reaction products is believed to be responsible for
increasing the overall antioxidant capacity of the foods.
Maillard pathway can produce several antioxidant com-
pounds with strong reducing power such as reductones and
amino-reductone that can inhibit low-density lipoprotein
(LDL) oxidation, and the concentrations of Maillard type
polymers are increased with increasing heat treatment [43].
Antioxidant activity in TBA method
During the oxidation process, peroxides are gradually
decomposed to lower molecular compounds, mainly mal-
ondialdehyde (MDA) [44] and their relative concentrations
are measured by TBA method. Malonaldehydes, one of the
lipid oxidation products can react with free amino group of
proteins, phospholipid, and nucleic acids leading to struc-
tural modification, which induce dysfunction of immune
systems [41]. At low pH and high temperature, MDA binds
TBA to form red complex and the absorbance can be
measured at 532 nm on the final day of the incubation
period (1 day after the control reached maximum absor-
bance in inhibition of linoleic peroxidation assay).
Antioxidant activity (as measured by TBA test, the data
given as absorbance values) of roasted peanut kernel flour
with and without skin is displayed in Fig. 4. In this method,
the lower the absorbance values the higher the antioxidant
activity. Interestingly, also in this assay, the antioxidant
activity of roasted peanut flour without skin was found to
be higher than those of unroasted sample and the control.
However, the present values were found to be significantly
(p\0.05) lower than those of positive controls (quercetin,
tocopherol, and BHA). These results also support that the
Maillard reaction products, probably formed due to roast-
ing of peanut kernel, are able to decrease the lipid oxida-
tion rate revealing antioxidant potential. The effect of
Maillard reaction products on lipid oxidation in preheated
model systems has been studied by Mastrocola and Munari
[45]. In their studies, the simultaneous induction of the
Fig. 3 Effect of roasting times on antioxidant activity of peanut flour
with and without skin as measured by percent inhibition of linoleic
acid peroxidation. Values with same small letters (a,b,c) are not
significantly different (p\0.05), among different roasting times.
Values with same capital letters (A,B) are not significantly different
(p\0.05) between the samples
604 Eur Food Res Technol (2011) 233:599–608
Maillard reaction in heated lipid fractions models greatly
affected the development of lipid oxidation by slowing the
reaction and increasing the antioxidant activity of the sys-
tem. Also in this assay, the antioxidant activity of roasted
and unroasted peanut flour with skin was not significantly
(p\0.05) different from those of quercetin and tocopherol
but lower than that of BHA. These results correlated well
with those obtained previously using the linoleic acid
emulsion method. It is well known that phenolic compounds
act as hydrogen donors and reduce the extent of formation
of hydroperoxides and lipid oxidation [46].
Individual phenolics composition measured by HPLC
Based on our preliminary trials, we observed that a number
of complex and unidentifiable peaks appeared in non-
hydrolyzed samples analyzed, which might be due to
detection of bound (esterified form) phenolics in conjunc-
tion with carbohydrates and other related moieties. HPLC
analysis of the hydrolyzed samples is the most recom-
mended and appreciating approach. Therefore, for sim-
plicity and clarity of the analysis, we used the hydrolyzed
samples for detection of target phenolic compounds. The
differences between control samples (non-hydrolyzed) and
hydrolyzed samples referring to polyphenols were consid-
ered during the quantification of phenolics final amounts in
the samples tested. HPLC chromatograms obtained for the
separation of standard phenolic compounds and the phe-
nolic compounds in roasted peanut kernel flour with skin
are given as Figs. 5and 6, respectively.
In the present study, three phenolic acids (p-hydroxy-
benzoic, chlorogenic, and p-coumaric), two flavonols
(quercetin and kaempferol), and stilbene (resveratrol) were
mainly detected in the tested samples as measured by RP-
HPLC. The data generated showing the effects of different
roasting times that affected the individual phenolic com-
pounds of peanut flour, with and without skin, are sum-
marized in Table 1. The results indicated that the contents
of phenolic acids, flavonols, and resveratrol in roasted
peanut kernel flour without skin were gradually increased
up to 20 min of roasting. Thus, in case of peanut kernel
flour without skin, after 20-min roasting, the concentration
of p-hydroxybenzoic acid increased from 133.49
to 146.00 lg/g, chlorogenic acid 32.01–37.16 lg/g and
p-coumaric acid 73.08–81.88 lg/g, respectively. Our
finding are in agreement with the work of Talcott et al. [15]
who reported that roasting increased the concentration of
the predominant antioxidant phenolic acid (p-coumaric
acid) in peanut that might be attributed to heat-catalyzed
hydrolytic reactions of its native esterified or bound forms
liberating into free forms. Naturally, polyphenols occur as
in both free and bound forms. Some processing methods
Fig. 4 Effect of roasting times on antioxidant activity of peanut
kernel flour with and without skin measured by TBA method. Values
with same small letters (a,b,c) are not significantly different
(p\0.05), among different roasting times. Values with same capital
letters (A,B) are not significantly different (p\0.05) between the
Fig. 5 HPLC chromatogram showing the separation of standard
phenolic compounds (1) gallic acid, (2)p-hydroxybenzoic acid, (3)
chlorgenic acid, (4) caffeic acid, (5) epicatechin, (6)p-coumaric acid,
(7) ferulic acid, (8) resveratrol, (9) quercetin, (10) daidzin, (11)
luteolin, and (12) kaempferol
Fig. 6 A typical HPLC chromatogram showing the separation of
phenolic compounds in roasted peanut kernel flour with skin (2)
p-hydroxybenzoic acid, (3) chlorogenic acid, (6)p-coumaric acid, (8)
resveratrol, (9) quercetin, and (12) kaempferol
Eur Food Res Technol (2011) 233:599–608 605
such as roasting have been shown to increase the poly-
phenolic content of foods probably due to releasing of
bound form antioxidants into free forms and coupled with
formation of Millard reaction products due to roasting
effects. Dabrowski and Sosulski [47] studied free and hy-
drolysable polyphenols in ten oil seeds including peanuts
wherein esterified forms of p-coumaric, ferulic, and caffeic
acids were detected in defatted peanut flour. It has been
revealed that the degree of roasting influenced the quality
and antioxidant properties of peanut kernels, creating a
complex environment for peanut quality assessment [15].
Flavonols (e.g., quercetin and kaempferol) are one of the
important classes of flavonoids that are secondary metab-
olites in plants and have beneficial effects for human health
because of their antioxidant, antiproliferative, and anti-
carcinogenic properties [23]. Recently, Wang et al. [23]
reported that peanut kernels contained trace amount of
kaempferol and higher amounts of quercetin than other
legumes. The presently determined amount of quercetin
(104.46 lg/g) in unroasted peanut kernel flour without skin
and 121.47 lg/g in unroasted peanut kernel with skin were
found to be lower than those reported by Wang et al. [23];
however, kaempferol content (1.56 and 2.31 lg/g, respec-
tively) was comparable with that of Wang et al. [23]. In
their report, peanut kernels (including skin) contained
higher amount of quercetin (133–289 lg/g) and its con-
centration mainly depended on kernel seed-coat color,
whereas kaempferol was 1.92–4.66 lg/g.
In the present study, the concentration of flavonols in
peanut kernel flour without skin was also affected as result
of roasting. The increase in concentration of quercetin from
104.46 to 133.00 lg/g and kaempferol from 1.56 to
2.68 lg/g as result of 20-min roasting may be linked to the
breakdown of flavonol glycosidic bonds to respective
aglycons under the thermal treatment. Zill-e-Huma et al.
[48] reported a similar phenomenon where, thermal treat-
ment led to the degradation of the quercetin glucosides and
increased the concentration of free quercetin aglycone in
microwave heated onion. It was also established that
roasting caused a slight increase, from 0.11 to 0.13 lg/g, in
the content of resveratrol. In contrary to our result, Sander
et al. [49] reported that roasted Virginia and Spanish pea-
nuts (176 °C) contained less amount of resveratrol than
that of unroasted ones. The differences in data obtained in
our study in comparison to those of Sander et al. [49] may
be probably due to different roasting temperatures
employed (160 °C vs. 176 °C).
On the other hand, in the present analysis, prolong
roasting ([20 min) slowly decreased the contents of
phenolics in peanut kernel flour without skin while a sig-
nificant (p\0.05) decline in the amounts occurred at
50 min roasting. It is understandable that practically up to
certain temperatures, the concentration of phenolic com-
ponents may increase due to improved cell wall rupturing,
or due to other favorable reactions, leading to their higher
recovery into the solvents; however, a prolonged heating
may decrease the concentration of naturally occurring
polyphenolics in food products [50]. A similar study on the
effect of different roasting process on carob powder indi-
cated that phenolic compounds were decreased after
75 min roasting at temperatures of 135, 150, and 165 °C
[31]. The present results indicate that an appropriate
Table 1 Phenolic compounds (lg/g) analyzed by HPLC in roasted peanut kernel flour with and without skin
Samples Phenolic acids Flavonols Stilbene
p-Hydroxybenzoic Chlorogenic p-Coumaric Quercetin Kaempferol Resveratrol
Kernel flour without skin (min)
0 133.49 ±12.91
32.01 ±3.49
73.38 ±2.98
104.46 ±6.27
1.56 ±0.27
0.11 ±0.01
10 141.00 ±1.00
34.00 ±1.00
76.00 ±4.00
110.00 ±3.00
2.60 ±0.50
0.12 ±0.03
20 146.00 ±6.00
37.16 ±2.12
81.88 ±5.54
133.00 ±6.00
2.68 ±0.10
0.13 ±0.00
30 141.50 ±3.50
33.79 ±1.22
75.79 ±4.33
134.41 ±4.86
2.37 ±0.09
0.08 ±0.00
40 132.50 ±7.50
35.27 ±2.25
59.44 ±6.67
128.50 ±1.50
1.44 ±0.05
0.08 ±0.00
50 112.80 ±4.80
23.04 ±0.22
51.62 ±3.55
81.56 ±3.44
0.96 ±0.10
0.03 ±0.00
Kernel flour with skin (min)
0 131.30 ±5.99
32.60 ±2.80
61.86 ±6.79
121.47 ±7.71
2.31 ±0.37
0.13 ±0.01
10 136.48 ±0.30
38.15 ±1.5
60.09 ±9.07
136.37 ±3.71
2.70 ±0.27
0.14 ±0.01
20 137.11 ±1.62
34.32 ±1.16
60.09 ±1.17
164.99 ±4.69
2.19 ±0.15
0.14 ±0.01
30 136.47 ±2.39
35.63 ±1.28
93.62 ±6.46
168.70 ±0.83
2.99 ±0.25
0.13 ±0.01
40 143.74 ±5.96
43.17 ±4.11
92.40 ±1.65
178.05 ±1.11
2.85 ±0.04
0.14 ±0.01
50 144.06 ±1.62
44.42 ±3.99
92.83 ±2.62
171.31 ±5.96
2.14 ±0.20
0.16 ±0.00
Values with same small letters (a, b, c) are not significantly (p\0.05) different among different roasting times. Values with same capital letters
(A, B) are not significantly (p\0.05) different between the samples
606 Eur Food Res Technol (2011) 233:599–608
roasting time (\20 min) should be employed to enhance
and/or retain optimum amount of phenolic compounds in
peanut flour without skin.
Interestingly, in case of roasted peanut kernel flour with
skin, the concentrations of phenolics, especially p-coumaric
acid and flavonol (quercetin), were linearly increased as
function of roasting times. As evident in Table 1, the ori-
ginal contents of p-coumaric acid (61.86 lg/g) and quer-
cetin (121.47 lg/g) were notably (p\0.05) enhanced after
30, 40, and 50 min roasting to levels as high as 93.62, 92.40,
and 92.83 lg/g and 168.70, 178.05, and 171.31 lg/g,
respectively. Improvement in phenolics contents and anti-
oxidant activity of peanut during roasting can be supported
from the literature. During heating process, compounds
with free amino groups such as lysine can undergo a
sequence of complex reactions with carbonyl compounds to
produce intermediate Maillard reaction products such as
furans and its derivatives like tetrahydrofuran (THF), mel-
anoidins, pyrroles, pyrazines, and other heterocyclic com-
pounds that not only impart color, flavor, and aroma to the
heated end-use products but also contribute to enhance the
antioxidant activity [16,51,52]. Melanoidins with high-
molecular weight are also one of the end products of
Maillard reaction and might have some antioxidant activity
[52]. However, Yanagimoto et al. [53] reported that pyra-
zine formed during roasting of coffee had no antioxidant
activity whereas furans and pyrroles exhibited minor anti-
oxidant activity. As peanut contain considerable amounts of
carbohydrates and amino acids, it is expected that Millard
reaction derived products might have been the major con-
tributor to enhancing the antioxidant attributes of peanut
during roasting. Therefore, it is possible to say that while
peanuts kernel were roasted with their skin intact, these
Maillard reaction products may interact with the mono-
meric and oligomeric proanthocyanidins present in peanut
skin generating some new antioxidant compounds [28,54].
It was reported that various oligomeric bridged com-
pounds were formed from the reaction between cyanidin-3-
O-glucoside and Maillard reaction products such as furfural
compounds that may play a major role in the flavanol
polymerization process [55]. Yu et al. [56] investigated that
proanthocyanidin (trimers and tetramers) content of peanut
skin decreased after roasting whereas its monomers content
increased. Saffan [57] also revealed that heat-stressed
peanut seedlings at 40 °C exhibited significantly
(p\0.05) higher polyphenolic contents (phenolic acids
and flavonoids) than those of the control. The other pos-
sible reason is that proanthocyanidin compounds most
likely condensed tannins, in peanut skin, have degraded
into simpler phenolics during heat treatment leading to
increasing the overall contents of phenolics [58]. Similar
phenomenon was reported by Rakic et al. [59] where, the
contents of gallic acid increased significantly following
thermal treatment of oak acorns, whereas those of hydro-
lysable tannins degraded resulting in an increase of simple
phenolics such as gallic acid. Additionally, the significant
increase in p-coumaric and quercetin contents at 30, 40,
and 50 min roasting times in this work may also be
explained either as a result of the breakdown of the
molecular structures containing phenolic groups or by the
thermal stability of these compounds.
Overall, in this research, the increase in the antioxidant
capacity of roasted peanut flour, with and without skin, can
be likely linked to better release of some antioxidant
phenolics such as phenolic acids, flavonols, and degrada-
tion of tannins to simple phenolics as well as due to the
contribution of Maillard reaction products following
roasting process. Obviously, a mixture of such compounds
might have contributed to enhanced antioxidant activity.
The results of this study revealed that roasting has signif-
icantly affected the antioxidant activity and the phenolic
composition of peanut flour, with and without skin. Inter-
estingly, the antioxidant activity and amounts of phenolic
compounds in peanut kernel flour with skin were appre-
ciably increased even up to 50-min roasting; however, the
longer roasting time ([20 min) resulted in the degradation
of phenolic compounds in peanut flour without skin.
Therefore, we suggest that proper roasting timing should be
taken into account to retain and/or enhance the natural
antioxidant phenolics of peanut flour with or without skin.
Based on the high phenolics concentration and superior
antioxidant capacity, the roasted peanut flour with skin can
be recommended for uses as a potential source of valuable
functional bioactives. Since peanut skin is often treated as
an agro-waste, it can be explored as a cheap and renewable
raw material for isolation of antioxidant compounds for
protecting other lipid containing food products, especially
the vegetable oils as well as an ingredient of functional
foods and nutraceuticals. Furthermore, an in-depth study on
structural elucidation of some novel antioxidants formed
during peanut roasting process is highly recommended.
Acknowledgments The authors are highly thankful to Oil Crop
Development Project (UTF/MYA/006) in Myanmar initiated by the
Ministry of Agriculture and Irrigation, Myanmar and FAO for
financing this study and the Universiti Putra Malaysia for providing us
for laboratory facilities.
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... μg/100 g). A previous study by Win et al. (2011) showed both raw and roasted peanuts did not contain luteolin [29]. Surprisingly, a recent study by Wu et al. (2021) reported no detection of free and bound forms of this compound in walnut kernel [30]. ...
... μg/100 g). A previous study by Win et al. (2011) showed both raw and roasted peanuts did not contain luteolin [29]. Surprisingly, a recent study by Wu et al. (2021) reported no detection of free and bound forms of this compound in walnut kernel [30]. ...
... Of the compounds presented in Table 3, resveratrol was not found in walnut and pumpkin seed. The resveratrol level of peanut (14.18 μg/100 g) in the present study was comparable to those reported previously by Win et al. (2011) and Chukwumah et al. (2012) [29,36]. Prior research has revealed that cashew, walnut, pumpkin, and sunflower seeds contained about 110-1410 μg of resveratrol per 100 g [31,33]. ...
Full-text available
The aim of the present study was to determine the phenolics, carotenoids, B-vitamins, and antioxidant activity of nuts and seeds grown in Vietnam. The concentrations of carotenoids and B-vitamins may vary among the nuts and seeds. Watermelon seed contained the highest level of lutein while pumpkin seed was the β-carotene richest sample. Sachi inchi and sunflower seed comprised considerable levels of vitamin B1, B6, and B9. The phenolic analysis revealed that cashew contained the highest total amount of flavonoids (466.04 μg/g), with catechin, epicatechin, and procyanidin B2 predominating over the other flavonoids. Likewise, chlorogenic and neochlorogenic acids made up the highest total amount of phenolic acids in sunflower seed (1870.41 μg/g). Walnut appeared to possess the highest antioxidant activity evaluated by DPPH, ABTS, FRAP, and reducing power assays. The correlation analysis indicated strong positive correlations between total phenolic content with DPPH and FRAP values. Principal component analysis graphically showed the distant positioning of cashew and sunflower seed, highlighting their significantly higher levels of phenolics. The findings of the study would be useful to improve nutrient database contents for flavonoids and phenolic acids as well as to promote the consumption of nut and seed products in Vietnam.
... The roasting partially destroyed the cell structures, resulting in the release of certain phenolic compounds, which could then become more extractable [22] [23]; 2) Compounds derived from Maillard reactions such as pyrrols and furans which could react with the Folin-Ciocalteu reagent [24] and other compounds with polyphenolic structures [25] could increase phenolic compound content. ...
... The availability of certain phenolic compounds released from certain polymers and in free form [24]. However, this increase of phenolic compounds by the presence of Maillard reaction products [25]. ...
... Literature data report large diversity in concentration of phenolic compounds, including flavonoids and aromatic acids among various types of nuts [3,29]. The most frequently identified flavonoids in nuts are catechin and epicatechin, which have been identified in hazelnuts, almonds, peanuts, pecans, walnuts and pine nuts [27,28,[53][54][55][56]. In tested nuts, catechin was not identified in pecans, walnuts, hazelnuts, Brazil and macadamia nuts, while epicatechin was not detected only in almonds. ...
... Moreover, literature data indicate that, among flavonoids, naringenin was determined in almonds and pistachios, quercetin in Brazil nuts, pistachios, cashews, pine nuts and peanuts, rutin in almonds, taxifolin in pine nuts, kaempferol in cashews and peanuts, genistein in pistachios and apigenin in almonds. In turn, vanillic acid was identified in almonds and Brazil nuts; cinnamic acid in Brazil nuts and cashews; coumaric acid in Brazil nuts, cashews and peanuts; syringic acid in Brazil nuts, cashews and pine nuts; and gallic and ellagic acids were determined in Brazil nuts, peanuts, cashews and pine nuts [14,29,53,54,56,[62][63][64][65][66]. Moreover, in most of the tested nuts, the presence of CAPE was found, a significant concentration of which was determined for pecans and peanuts. ...
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Edible nuts are an important component of a healthy diet, and their frequent consumption has beneficial impact on human health, including reducing the risk of cardiovascular and neurodegenerative diseases. Moreover, various factors, including cultivar, climate, soil characteristic, storage and treatment have influence on the chemical composition of nuts. Therefore, nine tree nut types and peanuts commonly available on Polish market were evaluated for phenolic profile and mineral elements content. The concentration of individual phenolic compounds, including flavonoids, aromatic acids and caffeic acid phenethyl ester (CAPE) was determined by ultra-high pressure liquid chromatography, while the content of macro-elements and trace minerals was analyzed by atomic absorption spectrometry. The phenolic profile of analyzed nuts substantially varied depending on the type of nut. The highest total content of all analyzed flavonoids was determined in walnuts (114.861 µg/g), while the lowest in almonds (1.717 µg/g). In turn, the highest total content of all tested aromatic acid was determined in pecans (33.743 µg/g), and the lowest in almonds (0.096 µg/g). Epicatechin and cinnamic acid were detected in the highest concentration in tested nuts. Moreover, in examined nuts (except walnuts and Brazil nuts), the presence of CAPE was confirmed. The tested nuts were also characterized by wide variation in element concentrations. Almonds contained high concentration of macro-elements (13,111.60 µg/g), while high content of trace elements was determined in pine nuts (192.79 µg/g). The obtained results indicate that the tested nuts are characterized by a significant diversity in the content of both phenolic compounds and minerals. However, all types of nuts, apart from the well-known source of fatty acids, are a rich source of various components with beneficial effect on human health.
... rate in MAP-treated fresh edible peanut kernels indicated that the lower oxygen concentration in MAP-treated samples could protect the fresh edible kernels against oxidative damage during storage (Shah et al., 2017), which was in agreement with the results reported in litchi (Ali et al., 2019) and papaya fruit (Hu et al., 2012). Phenolics and flavonoids are important secondary metabolites with natural antioxidant capacity, which can effectively scavenge free radicals and prevent the occurrence of cancer and cardiovascular and cerebrovascular diseases (Encarna et al., 2010;Win et al., 2011;Yang et al., 2020). Resveratrol, an antitoxin produced by plants, participates in reducing platelet aggregation, resisting cancer, and in preventing and treating cardiovascular and cerebrovascular diseases (Dixon, 2001;Baur and Sinclair, 2006). ...
In the present study, fresh edible peanuts were packaged with nitrogen and oxygen (N2: O2 = 9:1) (modified atmosphere packaging, MAP) or air (control) and stored at 4 °C for 120 d. The physio-chemical properties, enzyme activities, and antioxidant capacity of fresh peanut kernels were analyzed at different time points during storage to investigate the effect of MAP on the preservation of this product. In comparison with control, the MAP treatment could efficaciously maintain the commodity characteristics of fresh edible peanuts by inhibiting the browning, increasing the firmness, and decelerating the accumulation of malondialdehyde and hydrogen peroxidase, the production of superoxide anion, and the electrolyte leakage rate of fresh edible peanut kernels. In addition, MAP-treated peanut kernels exhibited higher activities of the enzymes in the phenylpropanoid pathway, including phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, and 4-coumarate-CoA ligase, and higher total phenolics, flavonoids and resveratrol contents. Activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase, and catalase, and antioxidant capacity [as measured by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant potential (FRAP)] were also maintained in the MAP-treated kernels. Furthermore, positive Pearson’s correlations were observed between FRAP and total phenolics (r² = 0.93), total flavonoids (r² = 0.91), and SOD (r² = 0.95), as well as between DPPH and SOD (r² = 0.89) and total flavonoids (r² = 0.77). Our results therefore suggest that MAP is a promising strategy to enhance bioactive compounds accumulation and activities of antioxidant enzymes in fresh edible peanuts during postharvest storage, hence providing valuable insights into preserving this important protein source.
... Phenolic acids, flavonoids, and stilbene are the main classes of phenolics present in peanut skin extracts. A study on the phenolic compounds of the skin, hull, raw kernel, and roasted kernel flour of peanuts found that peanut skin contained higher phenolic content and exhibited excellent antioxidant activity (Win et al. 2011). ...
Textile wet processing industry is one of the dreadful polluters in the world. An alternative to hazardous synthetic dyes could be dyes derived from various natural sources such as plants, insects, and minerals. Additionally, agro-waste and food processing waste could serve as effective sources of natural dyes. The current study focuses on extraction of natural dyes from two commercial food processing waste materials, namely, the spent coffee grounds and the roasted peanut skin. The dyes were found to possess rich tannin content and were applied on silk, cotton, and nylon fabrics with and without the aid of mordants using water bath and ultrasonic bath. The dye exhaustion percentage is better in water bath dyeing for spent coffee grounds dye while its vice versa for the roasted peanut skin dye. Both the dyes show good color fastness to washing with silk and nylon fabrics while the grades are poor in case of cotton. However, the myrobalan and alum mordanted cotton fabrics exhibit very good color fastness to laundering. The color fastness to light is below average as is the case with most natural dyes. The spent coffee grounds dye give yellow to light brown shades while the roasted peanut skin dye give pink shades on cotton, silk, and nylon fabrics. With the use of ferrous sulfate mordant the dyes give different shades of gray color.
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Background: Peanuts and tree nuts contain many bioactive compounds that may provide health benefits. There is some evidence to suggest that regular consumption of peanuts and peanut butter may improve cognitive function and mood, however, there are no prior studies examining whether daily intake of dry roasted, skinless peanuts improves cognition. Objective:The objective of this study was to determine the effect of consuming 49 g/day of peanuts for 12 weeks on cognitive function and mental health, compared to consuming a peanut-free diet, among healthy young women. Methods:This was a pre-post test study of 65 women (n = 32 in peanut group, n = 29 in control group). Participants in the peanut group consumed an individually portioned pack of peanuts each day for 12 weeks. Cognitive function was assessed using the CNS Vital Signs computerized neurocognitive test battery. Mental health was assessed using the Depression, Anxiety, and Stress Scale (DASS-42). Differences in endpoints between groups were assessed using ANCOVA tests. Results:There was a significant difference between the two groups in reaction time (6.9 points; p = 0.029), with the control group having a greater increase in scores. There was a significant within-group effect of peanuts on processing speed, with the peanut group increasing scores by 6.3 points (95% CI: 2.7, 9.8). There was no effect of peanut consumption on depression, anxiety, or stress scores. Conclusion:Further research is needed to fully understand the effect of different types of peanut products on cognition. Keywords: cognition, mental health, peanuts, nuts
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Processing of fruits, vegetables, and oil seeds results in high amounts of by-products. The purpose of this study is to investigate the physicochemical and techno-functional properties of grape (GS) and peanut skin (PS) by-products. Moisture, protein, fat, fiber, ash and carbohydrate of GS and PS powders were (7.37 and 2.34%), (6.76 and 5.59%), (2.55 and 20.68%), (12.91 and 14.19%), (6.62 and 1.87%) and (63.79 and 55.33%), respectively. Total phenolic compounds (TPC), flavonoids and antioxidant activity (DPPH radical scavenging) of GS and PS powders were (41.60 and 212.21 mg GE/gm d.w.), (3.99 and 16.83 mg quercetin equivalent / gm d.w.) and (10.88 and 63.30%), respectively. Both GS and PS powders had remarkable color attributes with promising role as a food natural colorant. GS powder has reddish-purple color with L* (lightness) value by (46.93), a* (redness) value (7.64), and b*(yellowness) value (6.87). While PS powder color ranging from light brown to deep red, with values of L*, a* and b* were (60.83, 9.23 and 16.77), respectively. Functional properties of the GS and PS powders (mesh 60 = 0.25 mm), both powders exhibited bulk density (0.999 and 0.457 g/ml), water absorption index (2.87 and 4.02 g/g), water solubility index (0.51 and 0.08 %), oil absorption index (1.50 and 1.70 ml/g) and swelling index (1.06 and 1.20 ml/g) for GS and PS powder respectively. Considering these results, it's clear that the GS and PS powders can provide an inexpensive source of dietary fibers and polyphenols for use as functional ingredients in foods or dietary supplements. Moreover, they had distinguished techno-functional properties. Such findings could introduce/valorize the GS and PS powders to play technological and health promoting desirable roles in many food products.
Peanut (Arachis hypogea L.) industrial processing generates underused by-products, which are mostly discharged. In this work, extracts from peanut by-product were obtained by Supercritical Fluid Extraction (SFE), Pressurized Liquid Extraction (PLE) and Subcritical Water Extraction (SWE), and compared to Soxhlet (SOX). Yield values varied from 12.94 to 37.65% for SOX-water and SWE, respectively. The quality of the extracts was evaluated by total phenolic content (TPC), antioxidant and enzymatic inhibition potentials, and fatty acids profile. Best TPC performance and high antioxidant capacity were obtained from samples using ethanol/water by PLE and Soxhlet. High inhibition of human salivary α-amylase was achieved by PLE and Soxhlet samples recovered with ethanol/water mixture. The inhibition of porcine pancreatic α-amylase was higher from samples by SFE and Soxhlet with ethanol. High-pressure methods are appealing alternatives for the recovery of bioactive extracts from peanut by-products, with functional properties and potential inhibitor of digestive enzymes.
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Peanut (Arachis hypogea L.) is one of the most consumed oil seeds worldwide. It belongs to the legume family and has spread to other parts of the world from South America. Peanut has been classified as Virginia, Runner, Spanish, and Valencia depending on the seed stagnation, branching pattern, the plant maturation period, and economic growth. People have consumed peanuts as raw, boiled, oil extracted, paste, roasted (snack), in energy bars and candies, and by adding paste to snack foods. Peanut and peanut products positively affect human health with their nutrients (lipid profiles) and bioactive compounds such as phytosterols, phenolic compounds, stilbenes, lignans, and isoflavonoids. These bioactive compounds protect against cardiovascular disease, type two diabetes mellites, and cancer. Peanuts consumption is recommended with the skin because of bioactive ingredients. In the Dietary Approaches Stop Hypertension diet model, peanuts consumption is recommended 4-5 times a week. Moreover, peanut takes place in traditional Mediterranean diet patterns, and its daily consumption is recommended. This review evaluated the relationship between peanut and peanut product consumption and health outcomes.
The food industry is generating huge amounts of by-products, about 1,890,000 tons, which should be better recycled into pharmaceuticals, cosmetics and functional foods, for instance, in order to save costs and avoid pollution. Here we review food by-products and methods of extraction. We present bioactive compounds from fruits, vegetable, tea, coffee, egg, nuts, meat and dairy products. Extracting methods include soxhlet, maceration, microwave, ultrasound, pressure.
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Antioxidant activities of defatted sesame meal extract increased as the roasting temperature of sesame seed increased, but the maximum antioxidant activity was achieved when the seeds were roasted at 200°C for 60 min. Roasting sesame seeds at 200°C for 60 min significantly increased the total phenolic content, radical scavenging activity (RSA), reducing powers, and antioxidant activity of sesame meal extract; and several low-molecular-weight phenolic compounds such as 2-methoxyphenol, 4-methoxy-3-methylthio-phenol, 5-amino-3-oxo-4-hexenoic acid, 3,4-methylenedioxyphenol (sesamol), 3-hydroxy benzoic acid, 4-hydroxy benzoic acid, vanillic acid, filicinic acid, and 3,4-dimethoxy phenol were newly formed in the sesame meal after roasting sesame seeds at 200°C for 60 min. These results indicate that antioxidant activity of defatted sesame meal extracts was significantly affected by roasting temperature and time of sesame seeds.
An ethanolic extract of roasted wheat germ was shown to scavenge free radicals, using the DPPH-test, and to protect DNA efficiently in vitro, using the 3D-assay. The DNA-protective activity of a coffee extract was comparatively lower and strongly dependent on the concentration applied. Fractionation of the wheat germ extract by preparative HPLC demonstrated that most of the DNA protecting properties were generated during the roasting process. Coupled GC–MS and HPLC–MS allowed identification of the main constituents of the active fractions. The contribution of genuine phenolic compounds was minor. Activity profiles of the radical-scavenging and of the 3D-assay test were not congruent. The attempt to extrapolate from in vitro measurements to the human in vivo situation is discussed.
Peanut kernels were roasted at 180±2°C for various period of times (0–60 min); then grounded and defatted or further hydrolyzed with proteases to test their antioxidative activity (AOA). Samples roasted for 60 min displayed the most remarkable AOA, determined by Ferric-thiocyanate method, on linoleic acid in emulsions prepared with Tween 20 or 80. In reducing power, the absorbance at 700 nm of enzymatic hydrolysates (1 mg/ml) prepared from a 60-min-roasted sample with Esperase (enzyme/substrate=1/200, 60°C, pH 8.0) and with Neutrase (enzyme/substrate=1/200, 50°C, pH 6.0) was 1.24 and 0.81, respectively. The scavenging activity of Esperase and Neutrase hydrolysates on DPPH (α, α′- diphenyl-β-picryldrazyl) radicals was 93 and 89%, respectively, while their chelating activity on Fe+2 was 69 and 52%, respectively. Besides, in vitro, Esperase hydrolysates (⩾100 μg/ml) exhibited the remarkable antioxidative effect on the oxidation of low-density lipoprotein (LDL) induced by copper by showing a lag time of longer than 6 h.
Peanut skin is a by-product of the peanut industry that has low economic value despite its high content of antioxidants such as phenolics. The effects of three skin removal methods (direct peeling, blanching, and roasting) and extraction solvents (water, ethanol, and methanol) on total phenolics and total antioxidant activities (TAA) of peanut skin extracts were studied, and the composition of extracts were determined by HPLC. Results show that both skin removal methods and extraction solvents had significant effects on total extractable phenolics and TAA, with the combination of roasting and ethanol extraction being the most efficient recovery method. One gram dry peanut skin contained 90–125 mg total phenolics. TAAs of water and ethanol extracts of peanut skin were 3.39 and 4.10 mM Trolox Equivalent/mM of total phenolics compared with 1.91 and 2.46, respectively, for green tea. Three classes of phenolics (phenolic acids, flavonoids, and stilbene) were found in peanut skin extracts.
Flavonoid content was quantified by high performance liquid chromatography (HPLC) and seed-coat colour was recorded from different legume seeds. Soybean seeds generally contained significantly higher amounts of daidzein (315–354 μg/g), genistein (438–458 μg/g), kaempferol (38–68 μg/g) and total measured flavonoids (892–917 μg/g), while cowpea and peanut seeds contained a significantly higher amount of quercetin (214–280 μg/g and 133–289 μg/g, respectively) than the other legumes tested. Significant variation for flavonoid content existed among and within legume species. Daidzein was significantly correlated with genistein and kaempferol (r = 0.92, P < 0.0001; r = 0.68, P < 0.0001), respectively. Genistein was also significantly correlated with kaempferol (r = 0.84, P < 0.0001). Due to differences in genetic background, no consistent relationship was observed between seed-coat colour and flavonoid content. Variation observed in flavonoid content and seed-coat colour would be useful for legume breeding programmes and consumer use.
The antioxidant effect of extracts from leaves, raw cortex, and roasted cortex of Du-zhong was evaluated using various lipid peroxidation models. The inhibitory activity of extracts of Du-zhong (200 μg/mL) on the peroxidation of linoleic acid measured by thiocyanate method followed the order leaves (99.9%) > roasted cortex (95.9%) > raw cortex (77.2%) at 60 h of incubation. The IC20 for leaves, roasted cortex, and raw cortex on the peroxidation of liposome, induced by Fe3+/H2O2/ascorbic acid, was <0.06, 0.24, and 0.81 mg/mL, respectively. The thiobarbituric acid reactive substances values for leaves, roasted cortex, and raw cortex were 0.12, 1.54, and 1.81 μmol of malondialdehyde/mg of protein in enzyme-mediated microsomal peroxidation and 0.08, 0.69, and 0.88 μmol of malondialdehyde/mg of protein in the nonenzyme-mediated microsomal peroxidation, respectively. The antioxidant activity of extracts of Du-zhong correlates to their polyphenol content. The results presented herein indicate that extracts of Du-zhong leaves may be useful in inhibiting membrane lipid peroxidation and preventing free radical-linked disease. Keywords: Du-zhong tea; water extracts; antioxidant activity; lipid peroxidation; free radical
The effect of varied maturity on the antioxidant activity of peanut hulls was investigated. Methanolic extracts of peanut hulls of varied maturity exhibited a similarly marked antioxidant activity, 92.9-94.8% inhibition of peroxidation of linoleic acid. The content of both luteolin and total phenolics increased significantly with maturity and seemed to show no correlation with antioxidant activity However, the antioxidant activity remained constant after 1.671 mg/g of hulls of total phenolic content was reached. Total phenolics (1.671 mg/g of hulls) in peanut hulls seemed to be an initial point of maximum antioxidant activity. High total phenolic content in peanut hulls of varied maturity is associated with a high antioxidant activity and with an important role in the stability of lipid oxidation.
ABSTRACTA crude mixture of catechins was isolated from Chinese green tea leaves using a hot water extraction. Individual catechins were then separated by chromatographic means using Sephadex LH-20 followed by semi-preparative HPLC. The antioxidant activity of crude and individual catechins was then determined in a β-carotene-linoleate model system. Results indicated that (−)-epicatechin-3-gallate (ECG) possessed the strongest antioxidative activity and (−)-epigallocatechin (EGC) showed the weakest effect. The antioxidative efficacy of (−)-epicatechin (EC) and (−)-epigallocatechin-3-gallate (EGCG) was similar and in between those of ECG and EGC. Furthermore, the antioxidant activity of a reconstituted catechin mixture in the proportions present in the crude extract was lower than that of the crude mixture itself, thus indicating that noncatechin components in the mixture possessed their own antioxidant activity or acted synergistically with the catechins.