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Even though carotenoid content in wheat grain is not very high,

wheat could provide signicant amounts of carotenoids as wheat is

readily found in most daily diets.   b-Carotene, zeaxanthin, cryp-

toxanthin and lutein are the major carotenoids and lutein is the

primary xanthophyll found in wheat (Khan & Shewry, 2009). Moore

et al. (2005)  reported that total carotenoid contents in eight soft

wheat varieties grown in Maryland ranged from 1.30 to 1.68  mg/g

and lutein was the most abundant carotenoid, 0.82e1.14 mg/g, fol-

lowed by zeaxanthin and  b-carotene. In another study lutein was

also found to be the predominant carotenoid, 0.97e2.43  mg/g, in

hard red winter wheat. Signicant amounts of zeaxanthin,   b-

cryptoxanthin and b-carotene were detected in wheat samples as

well (Zhou, Yin, & Yu, 2005). Carotenoid content of bran and germ

mixture was shown to be almost two-fold higher than that of the

wheat endosperm (Adom et al., 2005).

Information on organic acid content in wheat grain is limited.

Malic, aconitic and citric acids are the major organic acids in wheat

(Nelson & Hasselbring,1931). Seven varieties of two and four week-

old wheat grain samples were examined for their organic acid

content (Burke, Hilliard, Watkins, Russ, & Scott, 1985). Succinic,

malic, aconitic and citric acids were detected in the two weeks old

wheat while no succinic acid was detected in the four weeks old

samples indicating that compositional changes occur during graindevelopment.

Abrasive decortication or dehulling is a relatively inexpensive

process that has been used to separate bran and abraded grain in

small scale production facilities. Although bran fraction from

abrasive dehulling operation is expected to be rich in health

benecial phytochemicals, its potential for utilization in functional

foods has not been examined. Interest in plant extracts as rich

sources of health benecial bioactive compounds and antioxidants

continue to grow. Plant extracts are very complex mixtures of a

number of compounds that may interact synergistically. An un-

derstanding of the correlations between chemical composition and

antioxidant capacity of wheat grain fractions is critical for

designing ef cient separation techniques to produce antioxidant

rich products. Furthermore, formulation of nutraceutical productsfor specic health conditions entails the knowledge of relationship

between chemical composition and the function and effectiveness

of the product ingredients.

In a previous study we have reported that tangential abrasive

dehulling is an effective technique to obtain wheat grain fractions

with enhanced antioxidant properties (Chen, Dunford, & Goad,

2013a). Wheat grain fractions obtained by using a tangential

abrasive dehulling device (TADD) were characterized for their

proximate composition and antioxidant capacity. Phytosterol and

policosanols contents of the TADD fractions have also been re-

ported elsewhere (Chen, Dunford, & Goad, 2013b) The objective of 

this study is to characterize the phytochemical content and

composition (phenolic compounds, tocols and organic acids) of 

aqueous ethanol extracts of TADD fractions. Correlations betweenantioxidant capacity and the chemical compositions of the wheat

bran fractions are also developed.

2. Materials and methods

 2.1. Sample preparation

Intrada wheat was collected from Oklahoma State University

(OSU) variety testing program plots at Balko (100070W, 36060N),

Goodwell (101060W, 36060N), and Alva (36480700N, 983905700W)

in Oklahoma. Plots had eight 15 cmwide and 12m long rows. Seeds

were sown into a Ulysses silt loam (ne-silty, mixed, superactive,

mesic Aridic Haplustolls) at Balko; into a Richeld silt loam (ne,

smectitic, mesic Aridic Argiustolls) at Goodwell; and into a Grant

silt loam at Alva. All   elds were managed under   “grain only”practices. Detailed information on plant growth conditions were

reported elsewhere (Chen, 2011). Whole wheat grain samples were

collected after normal harvest. All the Intrada samples from

different locations were mixed prior to the experiments. A com-

mercial aleurone sample from Cargill Co. (Wayzata, MN, U.S.A.) was

included as a reference. Samples were stored in paper bags and

kept in a freezer at  20   C after being received in our laboratory

until the testing began within six months.

 2.2. Grain milling and extraction

Wheat grain fractions obtained by using a quadrumat senior

mill (C.W. Brabender Instrument, INC, South Hackensack, NJ,

USA) and a sieve tester (Gilson Company, Inc, Lewis Center, OH,

USA) (particle size over 500 mm) have been referred to as   “bran”in this study. Grain dehulling by TADD was described in detail

elsewhere (Chen et al., 2013a). Dehulling experiments were car-

ried out at 1, 3 and 5 min abrasion time and three grain moisture

levels, 15, 20 and 11% (the original wheat moisture level) by using

a TADD (Venables Tangential Abrasive Dehulling Device, Model

no. 4E-10/220, Venables Machine Works, Ltd, Saskatoon, SK,Canada). The distance between the abrasive plate (Coarse disc,

Type 4, Perten Instruments, Huddinge, Sweden) and the bottom

edge of the sample cups was set at 0.042 inch. Bran fractions

obtained from TADD processing were referred to as   “TADD

samples”   throughout this paper. Whole grain sample was pre-

pared by grinding the wheat kernels using a coffee grinder (Black

& Decker CBG5, Miami, FL, USA) at medium speed 3 times in 30 s

intervals.

The antioxidant extraction method used in this study was

adapted from literature (Adom & Liu, 2002;   Naczka & Shahidi,

2004). Ten grams of TADD, bran, aleurone, and whole wheat sam-

ples were extracted separately with 100 mL of ethanol at 80%, v/v,

in water for 16 h in the dark and under nitrogen at room temper-

ature (22   C). Extraction was repeated twice and extracts were

combined. Extract concentration was determined by evaporating

the solvent from 25 mL of extract under vacuum (35   C, 210e

240 mbar) and reported as mg solvent free extract/mL solvent. The

protocols used for ORAC, TPC and DPPH measurements were dis-

cussed in detail elsewhere (Chen et al., 2013a).

 2.3. Analytical tests

 2.3.1. Tocopherol and tocotrienols

Tocopherol and tocotrienol contents of the samples were

analyzed by using an HPLC system (Alliance 2690, Waters Corp.,

Milford, MA, USA) which consisted of a separations module (Model

2695) and a Photodiode Array Detector (PDA) (Model 2996, Wa-

ters). Two microliter of sample was injected into a normal phaseHPLC column, Zorbax RX-SIL (5  mm particle size, 4.6     250 mm,

Agilent Technologies, Santa Clara, CA, USA) and separation was

achieved by using a mobile phase consisting of hexane (HPLC

Grade, Fisher Scientist, Fairlawn, NJ, USA) and isopropanol (HPLC

grade, Pharmco Co., Brookeld, CT, USA) at a ratio of 99:1 (v/v).

Isocratic ow rate was 1.3 mL/min. Column temperature was set at

35  C (Katsanidis & Addis, 1999). Seven individual tocol standards,

a-tocopherol (a-T),   b-tocopherol (b-T),   d-tocopherol (d-T),   g-

tocopherol (g-T), a-tocotrienol (a-T3), b-tocotrienol (b-T3), d-toco-

trienol (d-T3) and g-tocotrienol (g-T3) were purchased from Sigma

(SigmaeAldrich Corporation, St. Louis, MO, USA) and used for peak

identication. The data collection and analysis were managed using

Waters Pro Empower software (Version 5.00.00.00, Waters Corp.)

running on a PC (DELL, XP-Professional, Round Rock, TX, USA).

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 2.3.2. Phenolic compounds

Phenolic acids in samples were analyzed by a Waters 2695 series

HPLC (Alliance 2690, Waters Corp.) equipped with a PDA (Model

2996, Waters Corp.) and a SunFire C18 (250 4.60 mm, 5 mm, Phe-

nomenex, Torrance, CA, USA) column. After   ltered through a

0.45  mm syringe  lter, 10 mL of sample was injected to the HPLC. A

mobile phase consisting of acetonitrile (solvent A) (HPLC grade,

VWR, West Chester, PA, USA) and 2 mL acetic acid in 100 mL water

(solvent B)was usedat a owrateof1.0mL/minforatotalruntimeof 

70 min. The solventgradient programwas as follows: 100 mL/100mL 

Bto85mL/100mLBin30min,85mL/100mLBto50mL/100mLBin

20min,50mL/100mLBto0mL/100mLBin5minand0mL/100mLB

to 100 mL/100 mL B in 15 min. Benzoic and cinnamic acids were

monitored at wavelengths, 280 and 320 nm, respectively. Gallic,

benzoic, vanillic, caffeic, syringic, p-coumaric and ferulic acids from

Sigma were used as standards. Data signals were acquired and pro-

cessed on a PC running the Waters Pro Empower software.

 2.3.3. Carotenoids

The carotenoid analysis was conducted by using a Waters HPLC

system equipped with a Waters 2487 dual-wavelength absorbance

detector, a Waters 600S controller, a Waters 616 pump, an inline

degasser, and a Waters 717 autosampler (Waters Corp.). Mobilephase consisted of HPLC grade methanol (Fisher Scientic, Pitts-

burgh, PA, USA) and deionized water from a Millipore water puri-

cation system (Millipore Corporation, Molsheim, France) at a ratio

of 95:5 (v/v) as solvent A and HPLC grade Methyl tert-butyl ether

(MTBE) (Mallinckrodt Baker, Inc. Phillipsburg, NJ, USA) as solvent B.

Isocratic elution was achieved with 75 mL/100 mL solvent A and

25% solvent B. Sample (10 mL) was injected to YMC Carotenoid S-3

column (250 4.6 mm, 3 mm column, Waters Corp.)at a owrate of 

1.9 mL/min. Column temperature was set at 35   C. The individual

carotenoid standards, lutein, zeaxanthin and   b-carotene from

Sigma were detected at 450 nm. Data signals were acquired and

processed on a PC (running the Waters Empower2 software

(Version 6.20.00.00, Waters Corp.)).

 2.3.4. Organic acids

The organic acids analysis was performed by using an Agilent

1200 Series HPLC system. The mobile phase, 0.005 M sulfuric acid,

was degassed by a Degasser (G1322A, Agilent, Santa Clara, CA, USA)

by using a Quad Pump (G1311A, Agilent). A Bio-rad Aminex HPX-

87H column (30    7.8 mm, Bio-rad, Hercules, CA, USA) equipped

with a guard column (30     4.6 mm, Bio-rad) were used for the

analysis. Sample, 5   mL, was injected by an autosampler (ASL,

G1329A, Agilent). Flow rate was 0.6 mL/min. Column temperature

was 35   C. A dual-wavelength absorbance detector (G1315D, Agi-

lent) was used to measure the absorbance of organic acids at

210 nm. Citric, ascorbic, malic, succinic, lactic and fumaric acids

from SigmaeAldrich were used as standards. Data signals were

acquired and processed on a PC running the ChemStation for LC 3Dsoftware (Rev. B.04.0x. Agilent).

3. Experimental design and statistical analysis

For TADD experiments a 3 3 factorial (1, 3 and 5 min abrasion

time and 15, 20 and 11 g/100 g moisture levels) design was used.

Three references (aleurone, Intrada bran, and whole wheat) were

also analyzed. The antioxidant capacity of TADD samples were

compared to the aleurone sample by using Dunnett’s multiple

comparisons method. Samples having signicantly higher or similar

antioxidant capacity as the aleurone were further analyzed for their

bioactive compounds. All the milling tests were carried out at least

in duplicate and in randomized order with the mean values being

reported. Analytical tests were performed in triplicate. The means

were compared using Tukey’s adjustment. Experimental data were

assessed for non-normality and heterogeneity of variances. Appro-

priate linear and generalized linear mixed models were analyzed

using version 9 SAS/GLM, SAS/MIXED and SAS/GLIMMIX procedures

(Software Version 9.2. SAS Institute Inc., Cary, NC).All statistical tests

were performed at the 0.05 level of signicance.

4. Results and discussion

The bran fractions obtained by using a TADD at various grain

moisture contents and abrasion times were labeled as follows:

TADD   e   Moisture content of the sample   e   abrasion time. For

example   “TADD-20-3” refers to the TADD sample obtained at 20 g/

100 g grain moisture content and 3 min TADD abrasion time. A

statistical analysis of the results obtained from three antioxidant

capacity tests, TPC, DPPH and ORAC, indicated that TADD-11-1,

TADD-15-1, TADD-15-3, TADD-20-3 and TADD-20-5 had higher

antioxidant capacity than the other TADD samples (Chen et al.,

2013a). Therefore, these samples were further analyzed for their

chemical composition focusing on the health benecial bioactive

compounds with antioxidant properties.

Although the same amounts of sample and solvent were used to

obtain all the extracts there were signicant differences in the

extract concentrations. Commercial aleurone resulted in the high-

est extract concentration and consequently highest extract amount

(Table 1). This is due to the very low starch content in the aleurone

sample and very low amount of aqueous ethanol soluble com-

pounds present in starch. Hence, extract yield varied with starch,

bran and oil content of the samples (Chen et al., 2013a). There were

signicant differences among the ORAC, TPC and DPPH of the ex-

tracts (Table 1). Although aleurone gave the highest extract yield,

the extract did not result in the highest ORAC value indicating that

the extract contained more material that did not possess oxygen

radical absorbance capacity than that in the TADD-11-1 and TADD-

20-5 extracts. Hence, phytochemical content and composition of 

the extracts were examined to evaluate the effect of extract

composition on antioxidant capacity as measured by differentmethods, ORAC, TPC and DPPH.

4.1. Tocopherols and tocotrienols

Whole wheat had the lowest tocols content, 3.02  mg/g sample

(Table 2). Aleurone (12.20   mg/g sample), TADD-20-3 (11.02   mg/g

sample), and TADD-15-1 (10.47mg/g sample) containedsignicantly

 Table 1

ORAC, TPC, DPPH and concentration of wheat extracts.

Samplea Extract

concentration

(mg/mL)

ORAC (mmol TE/g

of extract,

dry basis)

TPC (GE mg/g

extract,

dry basis)

DPPH (%

inhibition)

TADD-11-1 10.1 0.04B 478.7 21.8A 22.8 0.3B 42.6 0.4A

TADD-15-1 10.3 0.5B 256.6 11.7E 22.1 0.9B 41.2 0.4AB

T ADD -1 5-3 8 .4 0.4D 276.6 12.8D 26.4 1.1A 40.8 0.3B

T ADD -2 0-3 9 .2 0.2C 472.7 22.0B 23.0 0.8B 33.0 0.4C

T ADD -2 0-5 7 .7 0.03E 276.8 13.8D 26.2 1.1A 13.0 0.2E

Bran 10.1 0.1B 205.4 9.6F 19.7 0.5C 30.0 0.3D

Whole wheat 5.3 0.3F 159.3 7.7G 19.7 1.0C 9.8 0.1F

Ale urone 11.3 0.1A 411.6 20.9C 22.1 1.1B 42.4 0.2A

ABCDEFSample means within a column that have the same letter are not signicantly

different (a ¼ 0.05).

The data is reported as   “mean standard deviation”.a For TADD samples: TADD  e  moisture content  e  abrasion time, i.e. TADD-11-1

refers to bran obtained by using TADD at 11% (original) moisture level, 1 min

abrasion time. Whole wheat refers to the whole Intrada wheat sample. Bran and

aleurone refer to the bran from quadrumat mill and commercial samples,

respectively.

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content (free  þ  bound  þ conjugated) of the samples examined in

this study would be much higher than the amounts wereport here.

4.4. Organic acids

Whole grain had the lowest organic acid content (29.79 mmol/g

sample). TADD-15-1 (82.50 mmol/g sample) and bran (76.64 mmol/g

sample) had higher amount of organic acids than other samples(Table 5). Higher organic acid content in all TADD samples than the

aleurone indicates that organic acids are concentrated in the bran

fractions. Effect of grain moisture content and abrasion time

interaction on total organic acid content of the samples was sig-

nicant ( p < 0.0001,  F ¼ 226.86).

HPLC method used to analyze organic acids could not separate

ascorbic and malic acids. Hence results were reported as

ascorbic   þ   malic acids. Citric, ascorbic   þ   malic, succinic, and

fumaric acids were found in all the samples (Table 5). Succinic,

citric, and fumaric acids were the most abundant organic acids in

the samples. In aleurone, the succinic acid comprised approxi-

mately 73% of the total organic acids. Literature on organic acids

contents and compositions of wheat components are limited. Most

of the studies on organic acids were carried out on wheat leaves

(Burke et al., 1985; Clark, 1969). It has been reported that wheat

kernel had much greater organic acids contents than those found

in wheat leaves (Lohaus, Blos, & Rudiger, 1983). Malic, citric, suc-

cinic and fumaric acids were the major organic acids found in

wheat grain. The latter study reported higher amounts of organic

acids in wheat as compared to our study possibly due to the

different extraction method used.

4.5. Correlations between chemical composition and antioxidant 

capacity of the samples

Correlations between ORAC-DPPH [r  ¼ 0.48288, where r  refers

to Pearson Correlation (Coef cient)], ORAC-TPC (r  ¼ 0.45253) and

TPC-DPPH (r   ¼   0.71478) were all signicant ( p   <   0.0001) andpositive. The strongest correlation was found between TPC and

DPPH,   r  ¼   0.71478. Similar   ndings have been reported by other

research groups (Zhou, Su, & Yu, 2004; Zhou & Yu, 2004).

A positive and signicant correlation was found between DPPH

and total tocols (r  ¼   0.62777), phenolic acids (r  ¼  0.685000), ca-

rotenoids (r ¼ 0.52381) and organic acids (r ¼ 0.38060). DPPH has

been widely used to evaluate radical scavenging ability of phenolic

compounds which are strong quenchers of the DPPH radicals

(Fauconneau et al., 1997;   Villaño, Fernández-Pachón, Moyá,

Troncoso, & García-Parrilla, 2007). Phenolic acids have bothhydrogen donating and electron transfer ability (Rice-Evans, Miller,

& Paganga, 1996, 1997). DPPH radicals react with phenolic com-

pounds via two different mechanisms, hydrogen atom transfer

(HAT) or the single electron transfer (ET). In these reactions solvent

type plays a key role. The HAT mechanism is dominant when the

reaction takes place in apolar solvent while polar solvents such as

methanol or ethanol leads to ET mechanism (Foti, Daquino, &

Geraci, 2004). In our study, ET mechanism is expected to be

dominant since aqueous ethanol was used for the extraction and

DPPH tests. Tocols, carotenoids, and phenolic acids were shown to

have a signicant positive correlation with DPPH assay (Prior, Wu,

& Schaich, 2005). Tocols and carotenoids can stop oxidation by

donating a hydrogen atom to a free radical (Gurney et al., 1996;

Niki, Saito, Kawakami, & Kamiya, 1984; Terao, 1989).Contribution of individual compounds to antioxidant capacity

was calculated by using   r 2 selection method. Ferulic acid

(r 2 ¼  0.5497) was the strongest contributor to DPPH radical inhi-

bition properties of the extracts (Table 6).

As expected phenolic acid content was positively correlated

with TPC (r   ¼   0.83516,   r   <   0.0001). Caffeic acid was the most

important compound affecting the TPC result (r 2 ¼   0.8750)

(Table 6).

Benzoic, vanilic, syringic and coumaric acids also had signicant

and positive contributions to TPC.

Strong correlation between ORAC and tocols content of the

samples (r  ¼  0.75793,  p  <  0.0001) (Table 6) supports the peroxyl

radical scavenger properties of the wheat bran extracts. Total

phenolic acid (r ¼ 0.65813) and carotenoid (r ¼ 0.42861) contentsalso had positive and signicant correlation with ORAC. Phenolic

 Table 4

Phenolic acids content and compositions of wheat samples a (mg/g sample, dry basis).

Sample Benzoic acid Vanillic acid Caffeic acid Syringic acid   p-coumaric acid Ferulic acid Total phenolic acids content

TADD-11-1 6.1 0.2CD 5.8 0.1D 4.4 0.1B 4.7 0.2C 5.2 0.2ABCD 15.0 0.6A 41.2 0.9BC

TADD-15-1 6.2 0.09CD 5.8 0.08D 4.6 0.05B 4.4 0.03C 4.5 0.03D 8.6 0.3C 34.2 0.3D

TADD-15-3 7.8 0.2A 8.3 0.2B 5.0 0.08AB 7.6 0.3A 5.8 0.2AB 10.5 0.3BC 45.0 1.0AB

TADD-20-3 7.2 0.2AB 10.3 0.2A 4.9 0.1AB 7.1 0.1AB 6.1 0.1A 11.5 0.3B 47.2 0.6A

TADD-20-5 6.5 0.1BC 6.9 0.2C 4.8 0.1AB 5.0 0.1C 5.6 0.2ABC 8.7 0.3C 37.5 0.8CD

Bran 5.6 0.2D

6.2 0.1CD

4.8 0.09AB

7.2 0.1AB

4.8 0.1BCD

10.8 0.5B

39.5 0.7C

Who le wheat 3.4 0.01E 3.3 0.02E n.d.b 2.5 0.04D 2.4 0.1E 4.8 0.2D 16.3 0.1E

Aleurone 6.4 0.08BCD 9.6 0.3AB 5.4 0.2A 6.2 0.2B 4.7 0.2CD 12.9 0.2AB 45.1 0.9AB

ABCDSample means within a column that have the same letter are not signicantly different (a ¼ 0.05).a Refer to Table 1 for sample abbreviations.b n.d.: Not detected.

 Table 5

Organic acids content and compositions of wheat samples a (mmol/g sample, dry basis).

Sample Citric acid Ascorbic acid þ malic acid Succinic acid Fumaric acid Total organic acids content

TADD-11-1 17.9 0.2B 1.5 0.03A 25.0 0.7D 11.0 0.2D 55.3 0.9C

TADD-15-1 25.2 0.3A 1.5 0.04A 37.7 0.7A 18.1 0.2B 82.5 0.9A

TADD-15-3 22.7 0.4A 1.4 0.05A 21.2 0.8E 10.8 0.2D 56.0 1.0BC

TADD-20-3 24.4 0.4A 1.1 0.04B 19.8 0.6E 10.9 0.2D 56.2 0.8BC

TADD-20-5 18.3 0.4B 1.0 0.03C 28.8 0.5CD 14.0 0.2C 61.9 0.7B

Bran 23.2 0.3A 0.6 0.01D 32.0 0.4BC 20.9 0.3A 76.6 0.5A

Whole wheat 10.4 0.2C 0.3 0.005F 13.1 0.3F 6.1 0.06E 29.8 0.4E

Aleurone 1.1 0.03D 0.4 0.01E 34.1 0.5AB 11.0 0.2D 46.6 0.6D

ABCDSample means within a column that have the same letter are not signicantly different (a ¼ 0.05).a

Refer to Table 1 for sample abbreviations.

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acids are effective peroxyl radical scavengers because of their

hydrogen atom donation ability (Yeh & Yen, 2003). Correlation

between total organic acid content and ORAC was not signicant

( p  ¼   0.7312). Both ferulic acid-ORAC and  a-tocopherol  þ  a-toco-trienol-ORAC correlations were positive. Among the bioactive

compounds, ferulic acid was the highest contributor to the ORAC

values (r 2 ¼ 0.6282). Ferulic acid is a potent antioxidant due to its

phenolic nucleus and unsaturated side chain (Castelluccio, Bolwell,

Gerrish, & Rice-Evans, 1996). The   eCOOH substitution on the

phenol ring makes it easier for the ferulic acid to donate its

hydrogen atom (Nenadis, Zhang, & Tsimidou, 2003).

5. Conclusions

This study demonstrated that TADD was more effective than

quadrumat senior mill to obtain wheat bran fractions enriched in

health benecial phytochemicals. Effect of grain moisture content

and abrasion time on chemical composition of TADD samples wassignicant ( p   <   0.001). Considering that abrasive dehulling is a

relatively inexpensive technique and not dif cult to operate, it can

be suitable for small scale local production of specialty products.

TADD bran fractions can be utilized as ingredients in functional

food formulations. Extraction of TADD products with aqueous

ethanol would further concentrate phytochemicals with antioxi-

dant properties in the   nal product. These extracts could be

formulated into functional foods and nutraceuticals. The correla-

tions between chemical composition and antioxidant properties of 

TADD bran extracts developed in this study are helpful to formulate

products with desired ef cacy.

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 Table 6

Contribution of bioactive compounds to ORAC, DPPH and TPC assay as determined

by R-square selection method.

Compounds ORAC DPPH TPC

Ferulic acid 0.6282 0.5497 0.3800

a-Tocopherol þ a-tocotrienol 0.5904 0.2402   e

Vanillic acid 0.3673 0.2156 0.4197

 p-Coumaric acid 0.2693 0.2136 0.5851

Benzoic acid 0.2533 0.3540 0.7008Caffeic acid 0.2369 0.4293 0.8750

g-Tocopherol þ g-tocotrienol 0.2342 0.2402   e

Lutein 0.1857 0.2718   e

Zeaxanthin 0.1635 0.2986   e

b-Tocopherol 0.1615 0.0995   e

d-Tocopherol 0.1573 0.1000   e

Ascorbic acid þ malic acid 0.1269 0.2874   e

Syringic acid 0.0866 0.2513 0.3404

Fumaric acid 0.0397 0.0602   e

Citric acid 0.0177 0.0161   e

Succinic acid 0.0167 0.2093   e

Y. Chen et al. / LWT - Food Science and Technology 54 (2013) 353e 359358

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