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Food Hydrocolloids 39 (2014) 280e285

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Food Hydrocolloids

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Relationship between hydroxycinnamic profile with gelation capacityand rheological properties of arabinoxylans extracted from differentmaize fiber sources

Fabiola E. Ayala-Soto, Sergio O. Serna-Saldívar*, Esther Pérez-Carrillo, Silverio García-LaraCentro de Biotecnología-FEMSA, Escuela de Biotecnología y Alimentos, Tecnológico de Monterrey, Av. Eugenio Garza Sada 2501 Sur, C.P. 64849 Monterrey,N. L., Mexico

a r t i c l e i n f o

Article history:Received 10 September 2013Accepted 21 January 2014

Keywords:Arabinoxylans (AX)Maize fiber (MF)Nejayote (NE)Hydroxycinnamic acidsGelationRheological properties

* Corresponding author. Tel.: þ52 81 83284322; faE-mail address: sserna@itesm.mx (S.O. Serna-Sald

0268-005X/$ e see front matter � 2014 Elsevier Ltd.http://dx.doi.org/10.1016/j.foodhyd.2014.01.017

a b s t r a c t

The rheological properties and gelation capacity of arabinoxylans extracted from maize fiber (MFAX),resistant pericarp (RPAX), susceptible pericarp (SPAX) and nejayote (NEAX) were studied. The sugar andhydroxycinnamic acids profile of these extracts were previously characterized by Ayala-Soto, Serna-Saldívar, García-Lara, and Pérez-Carrillo (2014). A linear regression was established to study the rela-tionship between hydroxycinnamic profile of arabinoxylans (AX) and their gel properties. Swelling ca-pacity and Tan d were directly proportional with the amount of ferulic acid (FA), and inverselyproportional with dehydrotriferulic acid (tri-FA). For complex viscosity (h*) the relationship was inversedbecause higher values of complex viscosities (h*) were observed in gels containing higher and loweramounts of tri-FA and FA, respectively. According to these results, the percentage of tri-FA was the mostimportant in AX gelation. For this reason, the MFAX gels with the higher percentage of tri-FA showed themost elastic behavior followed by RPAX, SPAX and NEAX gels.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Arabinoxylans (AX) are non-starchy polysaccharides mainlylocalized in the endosperm cell walls, aleurone layer and thepericarp of cereal grains, their composition and degree of branchingdepend on their source. They are constituted of a linear b-(1,4)-D-xylopyranose backbone and L-arabinofuranose residues as sidechains on O-2 and/or O-3. This polymer can present some of thearabinose residues ester-linked to ferulic acid on O-5 positions (3-methoxy, 4 hidroxycinnamic acid) (Carvajal-Millán et al., 2007).Ferulic acid is important for the biology of the cell wall and itsstructure, because it can potentially cross-link polysaccharidechains through a dimerization reaction to form dehydrodimer (5-50,8-O-40, 8-50 and 8-80) and dehydrotrimer isomers (8-O-4/8-O-4, 8-8/8-O-4) (Funk, Ralph, Steinhart, & Bunzel, 2005; Saulnier &Thibault, 1999). Covalent bridges and physical interactions be-tween these structures are relevant in the gelation process and thefinal properties of AX gels, which are formed under oxidativecoupled cross-linking catalyzed by different enzymes such as lac-case and peroxidase (Berlanga-Reyes, Carvajal-Millán, Lizardi-Mendoza, Islas-Rubio, & Rascón-Chu, 2011; Niño-Medina,

x: þ52 81 83284262.ívar).

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Carvajal-Millán, Rascón-Chu, & Márquez-Escalante, 2010; Niño-Medina et al., 2009). Some studies have previously described theinteresting technological applications of AX gels mainly in the foodand pharmaceutical industries (Berlanga-Reyes et al., 2009;Carvajal-Millán, Landillon, Morel, Rouau, & Micard, 2005a; Kale,Pai, Hamaker, & Campanella, 2010). AX and their gels haveneutral taste and odor, high water absorption capacity (100 g ofwater/g AX) and absence of pH or electrolyte susceptibility, and alsoare stable under heating conditions. Furthermore, they do notsuffer syneresis after long time storage (Niño-Medina et al., 2010).Due to these properties, AX can be used as adhesive, thickener,stabilizer, emulsifier, controlled release matrix and film former(Carvajal-Millán et al., 2007; Hernández-Espinoza, Piñón-Muñiz,Rascón-Chu, Santana-Rodriguez, & Carvajal-Millán, 2012; Saeed,Pasha, Anjum, & Sultan, 2011; Yadav, Moreau, & Hicks, 2007; ).

The processing behavior of a product formulation can beconsidered as a direct manifestation of its rheological properties.The evaluation of these properties is significant to assess the impactof AX on the sensory quality of the final product (Kale et al., 2010),as well as in terms of their behavior as agents for the delivery ofbiomolecules. Some studies (Berlanga-Reyes et al., 2009;Hernández-Espinoza et al., 2012) demonstrated that the mixtureof insulin, b-lactoglobulin and lycopene with maize bran AX gel didnot affect the rheological gel behavior and importantly controlled

F.E. Ayala-Soto et al. / Food Hydrocolloids 39 (2014) 280e285 281

the release of the compounds at a rate dependent of the poly-saccharide concentration.

Due to potential technological applications of AX gels, isimportant a better understanding of the relationship between thepolymer structure and its gel forming properties. According to Kaleet al., (2010), a higher average molecular weight and size is asso-ciated with higher solution viscosity and extensional viscosity ofdoughs containing corn bran AX. Furthermore, these authorsobserved that at higher degree of AX branching was positivelyrelated to a higher resistance to extension. However, the hydrox-ycinnamic acids also play an important role in AX gelation. For thisreason it is necessary to establish a relationship between the con-centration of these compounds in the polymers and the viscoelasticbehavior of their gels. Determining the chemical structure of AXextracts with respect to the viscoelastic behavior of their gels couldbe an important factor to select the fiber source or to establish thecondition process to extract AX with the desired characteristics.The present study was undertaken to investigate the gelation ca-pacity and rheological properties of gels formed from AX extractedfrom different maize fiber sources, as well as the relationship be-tween these properties and the hydroxycinnamic profile of theextracts that were characterized in a preceding study by Ayala-Sotoet al., (2014).

2. Materials and methods

2.1. Plant materials

The four different maize fiber sources were the same as used inour previous study (Ayala-Soto et al., 2014). The first fiber (MF) wasobtained from commercial white maize through a wet-millingprocess and ground to pass the 0.5 mm sieve. This was providedfromMexstarch Industry Sapi de C.V. (Sinaloa, Mexico). The secondand third sources represent pericarps manually dissected from twocontrasting maize varieties, POB84C3 (insect-resistance) andCWL244X346 (insect-susceptible). Both pericarps were ground topass a 1.19 mmholed screen, and theywere named as resistant (RP)and susceptible (SP) pericarps, respectively. Finally, the fourthsource was nejayote (NE) obtained after nixtamalization of sus-ceptible white maize (variety Asgrow 773). Each source of fiber wasprepared in triplicates and stored at �20 �C until use.

The enzyme Laccase, extracted from Pycnoporus sanguineus(cinnabarinus), was generously provided from the EnvironmentalBioprocess chair of the Water Center for Latin America and theCaribbean from Tecnológico de Monterrey.

2.2. Arabinoxylans extraction

AX extraction protocol was previously described by Ayala-Sotoet al., (2014). Briefly, 3 g of the MF, RP and SP samples were sus-pended in 45 mL of sodium hydroxide (NaOH) 0.5 N at 25 �C andagitated on a rotatory shaker (100 rpm) during 8 h. The alkalinetreated solution was centrifuged (IEC Central MP4R NeedhamHeights, Ma) at 17,000� g and 20 �C during 15 min. The pellet waswashed with distilled water (20 mL) and centrifuged again(17,000� g at 20 �C, 15 min). The supernatant and wash water ofeach sample were mixed and acidified to pH 4 with 3 N hydro-chloric acid. The acidified supernatants were centrifuged(17,000� g, 15 min at 20 �C), filtered through 2.7 mm paper(Whatman), and then the filtrate precipitated with 65% (v/v)ethanol overnight at 4 �C. The precipitate was recovered bycentrifugation (16,000� g at 4 �C, 15 min) and air-dried (50 �C) for1 h to eliminate the ethanol. The maize fiber (MFAX), resistantpericarp (RPAX) and susceptible pericarp arabinoxylans (SPAX)were resuspended in water and freeze-dried (Virtis FM 25 EL 85,

Gardiner, NY). Each of these samples was stored at 4 �C. Theextraction of AX from 40 mL of nejayote (NEAX) was according tothe protocol described by Carvajal-Millán, Rascón-Chu, andMárquez-Escalante (2005b) with some modifications.

The AX extractions from fiber samples were performed intriplicates.

2.3. Detection and quantification of p-coumaric (p-CA), ferulic (FA),dehydrodiferulic (di-FA) and dehydrotriferulic (tri-FA) acids

Hydroxycinnamic acids were quantified in triplicates as previ-ously described Ayala-Soto et al., (2014). Hydroxycinnamic acidswere quantified by HPLCePDA (Agilent 1100 Santa Clara, CA)equipped with a Zorbax SB-Aq, 4.6 mm ID � 150 mm (3.5 mm)reverse column. The sample preparation first consisted in thealkaline treatment (2 N NaOH at 35 �C for 2 h), followed by acidi-fication to pH 2 with 4 N hydrochloric acid. Phenolics wereextracted twice with diethyl ether (500 mL). Ethyl ether phaseswere evaporated under nitrogen. Dried extracts were resuspendedwith 500 mL methanol 50% (HPLC grade). Each sample was filtered0.45 mm (syringe) and then injected (5 mL) into the column of theHPLC equipped with a PDA detector. Linear gradient elution wasperformed by HPLCewater acidified with trifluoroacetic acid (pH 2)and acetonitrile, at a flow rate of 0.6 mL/min at 25 �C (Chemstationfor LC Copyright � Agilent Technologies, 1990e2003). Peak iden-tification of ferulic and p-coumaric acids was based on retentiontime of authentic standards. The identification of di-FA and tri-FApeaks was performed in an HPLCeTOF-MS (mass spectrometry)at the conditions described above for HPLCePDA.

2.4. Swelling capability of the arabinoxylans gels

The swelling capability of the AX gels was determined accordingto the method described by Carvajal-Millán et al., (2005), withsome modifications. AX solutions (4% dry w/v) in pH 5 0.05 Mcitrate phosphate buffer were mixed with laccase (0.1 laccase U/mgof dried AX) and immediately transferred to a 5 mL tip-cut-off sy-ringe to allow gelation for 2 h at 25 �C. After the gelation process,every gel was weighed and placed in a glass vial with 5 mL of 0.02%sodium azide solution to swell during 6 h at 25 �C. The sodiumazide was employed to prevent microbial contamination.

The swelling ratio was calculated as: q ¼ (Ws �Wd)/Wd.Where, Wswas theweight of swollen gels andWd theweight of

polysaccharide in the gel.The increase of volumewas also calculated in a 5mL syringe, the

initial gel volume was measured after the 2 h of gelation and thefinal volume after 6 h of swelling, the volume increase was calcu-lated as: volume increase ¼ final volume� initial volume.

All the measurements were performed in triplicates.

2.5. Rheological properties

The viscoelastic behavior of AX gels was studied through a timesweep for 2 h using a rheometer (Anton Paar) working in theoscillatory mode. Solutions of 4% (w/v) MFAX, RPAX, SPAX andNEAX in citrate phosphate buffer (pH 5) were mixed with laccase(0.1 laccase U/mg of dried AX) and immediately placed in the coneeplate geometry (50 mm of diameter, 1� of angle) at 25 �C with a %deformation (ɣ) and frequency selected previously through anamplitude and frequency sweep. The amplitude sweep of AX wascarried out after 2 h of gelation (performed as previously described)at 1.59 Hz of frequency, 25 �C from 0.01 to 100% ɣ. The grade ofdeformation was selected according to the graphics of % ɣ againststorage modulus (G0) and loss modulus (G00), in which both moduliwere into the linear viscoelastic region (point without breakdown

F.E. Ayala-Soto et al. / Food Hydrocolloids 39 (2014) 280e285282

of the gel structure). The mechanical spectra was obtained by afrequency sweep from 0.1 to 10 Hz at 25 �C based on the % ɣselected. In the same way, at the chosen frequency, the gels shouldnot reached the ‘breaking point’ (where bothmoduli G0 and G00 werenot intersected) to avoid a viscous and promote an elastic (G00 > G0)behaviors and obtain measurements without affecting the gelstructure. All measurements of time sweep were carried out intriplicates at 25 �C with a frequency of 0.25 Hz and 5% strain.

2.6. Statistical analysis

All analyses were done in triplicates and the results wereexpressed as mean � standard deviations. Statistical analyses wereconducted by one-way ANOVA, and differences among meanscompared using Tukeys tests with a level of significance of p< 0.05.Linear regressions were performed to determine the relationshipsbetween gel properties and the hydroxycinnamic profile of AXextracts.

3. Results and discussion

3.1. Relation of hydroxycinnamic acid concentration of AX extractswith their gels properties

The hydroxycinnamic acids profile and concentrations of AXextracts were previously reported and discussed by Ayala-Sotoet al., (2014). In this research, we analyzed the percentage of FA,p-CA, di-FA and tri-FA with respect to the total of hydroxycinnamicacids (Table 1). All AX extracts had the higher percentage ofhydroxycinnamic acids in FA, especially those extracted from sus-ceptible maize varieties, SPAX and NEAX. This demonstrated thatthese molecules associated to cell-walls are less branched as pre-viously described by García-Lara et al., (2004). The compound withthe second highest abundance was di-FA except for the MFAX, inwhich p-CA was the second highest. A comparison between SPAXand NEAX indicated that the relative distribution of hydroxycin-namic acids was different, especially in terms of tri-FA that wasalmost the half in the NEAX extract (Table 1). Previous in-vestigations have documented that the combined effect of alkalineand thermal processing during lime-cooking or nixtamalizationenhances the hydrolysis of fiber components associated with cellwalls liberating ferulic moieties to the cooking-liquor commonlyknown as nejayote (González, Reguera, Mendoza, Figueroa, &Sánchez-Sinencio, 2004; Gutiérrez-Uribe, Rojas-García, García-Lara, & Serna-Saldívar, 2010; Mora-Rochin et al., 2010). In accor-dance with our results, tri-FA was the hydroxycinnamic acid withthe highest susceptibility to hydrolysis during nixtamalization. Thepercentage of tri-FA was higher in RPAX than MFAX because of theeffect of maize genotype. It is known that the insect-resistantmechanism is highly correlated with hydroxycinnamic acid con-centrations in the maize pericarp (García-Lara et al., 2004).

Table 1Amounts of p-coumaric acid (p-CA), ferulic acid (FA), dehydrodiferulic (di-FA) and dehydro(mg/mg AX dry extract) of the arabinoxylans extracted from different maize fiber source

Maize fiberarabinoxylans (MFAX)

Resistant parabinoxyl

Total of hydroxycinnamicacidsa

0.90 � 0.07 c 1.89 � 0

FA 57.78% � 8.44% c 63.33% � 1p-CA 14.44% � 1.11% a 11.64% � 0di-FA 13.33% � 1.11% b 15.34% � 0tri-FA 12.22% � 1.44% a 10.05% � 0

Values are means of triplicates. Values in each row with no letter in common are signifia Results are expressed in mg/mg dry AX extract. (Adapted from Ayala-Soto et al., 201

3.2. Swelling capacity

Water absorption or swelling capacity (q) values of AX gels aredepicted in Table 2. SPAX gels had the highest values followed byRPAX and MFAX gels, which were statistically similar (P > 0.05)despite the higher total concentration of hydroxycinnamic acids inthe RPAX extract (Table 2). On the other hand, the measurement ofq was not possible in the NEAX gels because of its weak structure,failure to swell and higher degree of solubilization.

Swelling capability is a measurement inversely proportional tothe strength of AX gels, where higher q values represent a weakpolymeric gel structure with high water absorption (Berlanga-Reyes et al., 2011). Recent studies have demonstrated (Berlanga-Reyes et al., 2011; Hernández-Espinoza et al., 2012) that the gela-tion capacities of AX are related to the cross-linking structuresbetween di-FA and tri-FA, as well as their molecular conformationsand interactions. In other words, a higher ferulic acid concentrationproduces stronger AX gels. In accordance to q values, the SPAX gelhad a comparatively weaker structure compared to MFAX andRPAX counterparts. The fitted equations and R2 of q versus thepercentage of each hydroxycinnamic acid showed a linear rela-tionship between q and FA concentration with the followingequation q ¼ 0.838 (FA) þ 1.9139 and R2 ¼ 0.941. This means thathigher FA concentrations resulted in higher swelling capacity. Onthe other hand, the inversed effect was observed with p-CA or tri-FA. At higher concentrations of these compounds showed lowerswelling capacities. The equations were q ¼ �1.9057 (p-CA) þ 77.612, R2 ¼ 0.899 and q ¼ �2.4436 (tri-FA) þ 79.998,R2 ¼ 0.904.

3.3. Rheological properties

The amplitude sweeps of the AX gels with the exception of theNEAX sample are depicted in Fig.1. The NEAX samples formedweakgels that were susceptible to amplitude changes resulting inirregular G0 values. Furthermore, the G00 mudulus dominated overthe G0 modulus thus showing a fluid behavior. Thus, the relativelyhigh frequency (1.59 Hz) used during the tests negatively affectedthe structure of the NEAX gels. The linear viscoelastic range of gelswas demonstrated through the amplitude sweep, in which bothstorage (G0) and loss (G00) moduli were constants and the gelstructures were not broken at a determined percentage of defor-mation (%ɣ) (Núñez-Santiago, Méndez-Montealvo, & Solorza-Feria,2001). The G0 is related with the elastic behavior whereas G00 withthe viscous resistance. When the value of G0 decreases and G00 in-creases, the peak resistance or gel ‘breaking point’ is reached. The‘breaking point’ of MFAX and RPAX gels was at 10 %ɣ whereas forthe SPAX gel at 20 %ɣ. Thus, the SPAX gels were the weakest withthe lowest G0 values (Fig. 1). However, these gels were more flexibleand resistant at the different grades of deformation. The strain

trifeulic acids (tri-FA) with respect to the total hydroxycinnamic acids concentrations.

ericarpan (RPAX)

Susceptible pericarparabinoxylans (SPAX)

Nejayotearabinoxylans (NEAX)

.01 a 1.21 � 0.05 b 1.04 � 0.05 c

.06% b 71.90% � 2.23% a 72.12% � 2.88% a

.69% b 8.26% � 0.41% c 10.38% � 0.48% b

.79% a 12.40% � 0.74% b 14.42% � 0.87% a

.32% b 7.44% � 0.41% c 3.85% � 0.29% d

cant different (P < 0.05).4).

Table 2Swelling capability (after 6 h at 25 �C in 5mL of 0.02% sodium azide solution) and rheological parameters (h* and tan d resulted from the sweep time for 2 h at 5% ɣ, 0.25 Hz and25 �C in oscillatory mode using a cone-plate geometry) of gels formed with 4% (w/v) of arabinoxylans extracted from different maize fiber sources under the action of laccaseenzyme (0.1 laccase U/mg of dried AX).

Gel q h* (Pa s) tan d (G00/G0)

t: 0 min t: 80 min t: 120 min t: 0 min t: 80 min t: 120 min

MFAX 51.39 � 2.31 b 0.648 � 0.006 b 47.600 � 0.001 a 50.067 � 0.057 a 0.794 � 0.001 c 0.008 � 0.000 d 0.009 � 0.000 dRPAX 53.25 � 2.72 b 0.204 � 0.000 b 23.400 � 0.002 b 29.767 � 0.153 b 1.680 � 0.005 b 0.021 � 0.001 c 0.019 � 0.000 cSPAX 61.83 � 2.72 a 0.129 � 0.001 b 10.200 � 0.005 c 12.167 � 0.058 c 2.630 � 0.000 a 0.067 � 0.000 b 0.059 � 0.001 bNEAX Without value 4.860 � 0.000 a 5.290 � 0.001 d 5.900 � 0.000 d 0.667 � 0.003 d 0.389 � 0.002 a 0.368 � 0.002 a

Values are means of triplicates. Values in each column with no letter in common are significant different (P < 0.05).q: Swelling ratio.h*: Complex viscosity.

F.E. Ayala-Soto et al. / Food Hydrocolloids 39 (2014) 280e285 283

value to performmechanical spectrumwas 5% because at this pointnone of the AX gels, including NEAX, reached the ‘breaking point’.

Frequency sweep is an oscillatory test where the rheologicalsample behaviors are obtained at different frequency changes inorder to obtain the mechanical spectrum (Fig. 2). The G0 modulusof NEAX gels appeared from 0.1 to 2.5 Hz. At higher frequencies(>than 3 Hz) the samples did not show G0 values (graphic notreported). Interestingly, the NEAX gels showed a fluid-likebehavior. All other samples behaved like a solid-like materialwith a characteristic gel behavior, in which the linear elasticmodulus (G0) was independent of frequency and the loss modulus(G00) was lower and dependent of frequency. Previous in-vestigations (Berlanga-Reyes et al., 2009; Hernández-Espinozaet al., 2012; Martínez-López et al., 2011; ) have reported similarmechanical spectrums.

Fig. 1. Amplitude sweep of 4% (w/v) AX solutions gelled for 2 h at 25 �C under the action ofmodulus), G00 (loss modulus).

The time sweep was carried out to study the evolution of G0 andG00 moduli during the oxidative gelation of AX extracts under theaction of laccase enzyme for 2 h (Fig. 3). All the AX gels showed atypical development of both moduli, where the G0 modulus had agradual increase followed by a plateau region and the G00 moduluswas constant. This means that the selected values of strain andfrequency selected to time sweep did not affect the gelation ofNEAX. Previous investigations have reported similar AX gel behav-iors (Berlanga-Reyes et al., 2009; Carvajal-Millán, Landillon, et al.,2005; Hernández-Espinoza et al., 2012). The MFAX gel had thehighest G0 modulus values at the plateau region with 50.07 Pa, fol-lowed by the RPAX (29.8 Pa), SPAX (12.2 Pa) and NEAX (5.9 Pa) gels.With respect to G00 modulus values, an inverse order was observedbeing first the NEAX gels (3.22 Pa), followed by the SPAX (1.12 Pa),RPAX (0.89 Pa) andMFAX (0.47 Pa) gels. Thus, theMFAXgels showed

laccase enzyme (0.1 laccase U/mg of dried AX). a) MFAX. b) RPAX. c) SPAX. G0 (storage

Fig. 2. Frequency sweep of AX gels at 5% ɣ and 25 �C. a) MFAX. b) RPAX. c) SPAX.. G0 (storage modulus), G00 (loss modulus). The gels were formed from 4% (w/v) AX solutions at 25 �Cduring 2 h under the action of laccase enzyme (0.1 laccase U/mg of dried AX).

F.E. Ayala-Soto et al. / Food Hydrocolloids 39 (2014) 280e285284

the most elastic and least viscous behaviors. Contrarily, the NEAXgels showed themost viscous and least elastic behaviors supportingthe results of swelling capacity mentioned before.

Table 2 shows the values of complex viscosity and Tan d (G00/G0) ofthe different AX gels. Values of complex viscosity (h*) are the totalresistance to deformation of viscoelastic liquids or solids, because itconsiders bothmoduli (Núñez-Santiago et al., 2001). The parameter

Fig. 3. Viscoelastic behavior of AX gel formation through time at 5% ɣ and 0.25 Hz a) MFAX. bstarted after the addition of laccase enzyme (0.1 laccase U/mg of dried AX) in 4% (w/v) AX

Tan d represents a relationship betweenmoduliG00 andG0.When thevalue is higher than 1, the material behaves like a viscoelastic liquidandwhen lower than 1 like a viscoelastic solid (Dap�cevi�c-HadnaCev,HadnaCev, & Torbica, 2009). All samples showed an increase in h*during the gelation process indicating the increase of cross-linkedstructures. After 2 h of gelation, the MFAX gels had the highest h*value followed by the RPAX, SPAX and NEAX samples (Table 2). On

) RPAX. c) SPAX. d). NAX. G0 (storage modulus), G00 (loss modulus). The gelation processsolutions.

F.E. Ayala-Soto et al. / Food Hydrocolloids 39 (2014) 280e285 285

the other hand, the value of tan d decreased in all the AX gelsindicating the formation of a more elastic material. MFAX gelsshowed the highest elasticity with the lowest ratio between G00 andG0, followed by RPAX, SPAX and NEAX (Table 2). Despite their low h*and G0 values, an elastic material with high sensibility to amplitudeand frequency changes was obtained from NEAX.

The gel rheological properties (Tan d and h*) were affected bythe FA, p-CA and tri-FA concentrations. Concerning complex vis-cosities, the fitted equations were h* ¼ �2.804 (FA) þ 210.3 withR2 ¼ 0.975, h* ¼ 5.18 (tri-FA) e 18.881 with R2 ¼ 0.893 for, andh* ¼ 6.999 (p-CA) þ 62.001 with R2 ¼ 0.789. It means that at lowerconcentration of FA and higher concentrations of p-CA and tri-FAproduced more elastic gels with higher G0 values, indicating thespecial relevance of tri-FA in the gelation process. A significantlogarithm relationship was observed for Tan d and amounts ofhydroxycinnamic acids. For this reason, it was necessary to plot thelog Tan d in order to generate a lineal regression. This relationshipresulted positive with FA (log Tan d ¼ 0.0904 (FA) - 7.3538,R2 ¼ 0.792), and inversed with tri-FA (log Tan d ¼ �0.195 (tri-FA)þ 0.279, R2¼ 0.996). In other words, at higher concentrations ofFA the gel behaved as a liquid whereas at higher tri-FA concentra-tions like a solid viscoelastic material.

Intriguingly, the MFAX contained a tri-FA concentration lowerthan RPAX when values were expressed as mg of FA equivalents/mgAXdryextract (Ayala-Soto et al., 2014).Whenvalueswere expressedas percentage of tri-FA with respect to the total hydroxycinnamicacid concentration, an inverse order was observed. This demon-strated that the relative percent distribution of the hydroxycin-namic acids was more important in the gelation capacity than theconcentration of each type of chemical compound. Furthermore,previous studies have reported that oxidative gelation of AXextractsnot only depends on the covalent cross-linked structures of di-FAand tri-FA but other covalent or no covalent crosslinked structures(Carvajal-Millán et al., 2007; Lapierre, Pollet, Christine, Ralet, &Saulnier, 2001; Niño-Medina et al., 2009). This might explain thestrongest gel structure observed in the MFAX. The concentration ofother structures present, including lignin, may be higher in MFAXthan the rest of AX extracts. Unlike the MFAX, the RPAX and SPAXsamples were extracted frommanually dissected pericarps withoutcontamination from other kernel components. The NEAX extractswere obtained from stronger extraction conditions (thermal lime-cooking or nixtamalization) that notably affected the crosslinkingstructures decreasing the gelation capacity. This agrees withLapierre et al., (2001), who demonstrated that AX extracts withlignin concentrations lower than 0.1% were unable to gel. Furtherstudies of how lignin concentrations in AX extracts and gels affectgelation capacity are required.

4. Conclusions

The gel rheological properties of AX extracts varied among thefour types of maize sources because of their differences inhydroxycinnamic acid profiles. In this research, we demonstratedconsistently through regression analyses the great relevance of tri-FA (expressed as a percentage of total hydroxycinnamic acid con-centration) in the AX gelation capacity and viscoelastic behavior. Athigher percentages of this compound the gel behaved more elastic.Also an inverse relationship was observed between the gel strengthand the amounts of FA. The values of G0 moduli were related to thehardness of the gel structure. The MFAX gels were the strongestfollowed by RPAX, SPAX and NEAX counterparts. NEAX gels had theweakest structure because the nixtamalization process and condi-tions enhanced the hydrolysis of fiber components mainly tri-FA.

Results presented herein indicated that the maize fiber obtainedfrom the wet-milling process was the best source of AX, because it

yielded the highest amount of gel (Ayala-Soto et al., 2014) andformed the more elastic gel structure.

Acknowledgments

The authors wish to acknowledge the financial support of Tec-nológico de Monterrey, Biotechnology research chair (CAT-005)and CONACYT. They also acknowledge to Environmental Bioprocesschair, Water Center for Latin America and the Caribbean fromTecnológico deMonterrey for providing samples of laccase enzyme.

References

Ayala-Soto, F. E., Serna-Saldívar, S. O., García-Lara, S., & Pérez-Carrillo, E. (2014).Hydroxycinnamic acids, sugar composition and antioxidant capacity of arabinox-ylans fromdifferentmaizefiber sources. Journal of FoodHydrocolloids, 35, 471e475.

Berlanga-Reyes, C. M., Carvajal-Millán, E., Lizardi-Mendoza, J., Islas-Rubio, A., &Rascón-Chu, A. (2011). Enzymatic cross-linking of alkali extracted arabinox-ylans: gel rheological and structural characteristics. International Journal ofMolecular Sciences, 12, 5853e5861.

Berlanga-Reyes, C. M., Carvajal-Millán, E., Lizardi-Mendoza, J., Rascón-Chu, A.,Marquez-Escalante, J. A., & Martínez-López, A. L. (2009). Maize arabinoxylangels as protein delivery matrices. Molecules, 14, 1475e1482.

Carvajal-Millán, E., Landillon, V., Morel, M. H., Rouau, X., & Micard, V. (2005a).Arabinoxylan gels: impact of the ferulation degree on their structure andproperties. Biomacromolecules, 6, 309e317.

Carvajal-Millán, E., Rascón-Chu A., & Márquez-Escalante, J. (2005b). Mexican PatentPA/a/2005/008124. Método para la obtención de goma de maíz a partir dellíquido residual de la nixtamalización del grano de maíz.

Carvajal-Millán, E., Rascón-Chu, A., Márquez-Escalante, J., Micard, V., Ponce deLeón, N., & Gardea, A. (2007). Maize extraction gum: characterization andfunctional properties. Carbohydrate Polymers, 69, 280e285.

Dap�cevi�c-HadnaCev, T. R., HadnaCev, M. S., & Torbica, A. M. (2009). Utilization ofdynamic measurements for agar threshold gel concentration and gel strengthdetermination. Food Processing, Quality and Safety, 38, 69e73.

Funk, C., Ralph, J., Steinhart, H., & Bunzel, M. (2005). Isolation and structuralcharacterisation of 8-O-4/8-O-4 and 8-8/8-O-4-coupled dehydrotriferulic acidsfrom maize bran. Phytochemistry, 66, 363e371.

García-Lara, S., Bergvinson, D. J., Burt, A. J., Ramputh, A. L., Díaz-Pontones, D. M., &Arnason, J. T. (2004). The role of pericarp cell wall components in maize weevilresistance. Crop Science, 44, 1546e1552.

González, R., Reguera, E., Mendoza, L., Figueroa, J. M., & Sánchez-Sinencio, F. (2004).Physicochemical changes in the hull of corn grains during their alkaline cook-ing. Journal of Agricultural and Food Chemistry, 52, 3831e3837.

Gutiérrez-Uribe, J., Rojas-García, C., García-Lara, S., & Serna-Saldívar, S. O. (2010).Phytochemical analysis of wastewater (nejayote) obtained after lime-cooking ofdifferent types of maize kernels processed into masa for tortillas. Journal ofCereal Science, 52, 410e416.

Hernández-Espinoza, A., Piñón-Muñiz, M., Rascón-Chu, A., Santana-Rodriguez, V., &Carvajal-Millán, E. (2012). Lycopene/arabinoxylan gels: rheological andcontrolled release characteristics. Molecules, 17, 2428e2436.

Kale, M. S., Pai, D. A., Hamaker, B. R., & Campanella, O. H. (2010). Structure-functionrelationships for corn bran arabinoxylans. Journal of Cereal Science, 52, 368e372.

Lapierre, C., Pollet, B., Christine, M., Ralet, M., & Saulnier, L. (2001). The phenolicfraction of maize bran: evidence for lignin-heteroxylan association. Phyto-chemistry, 57, 765e772.

Martínez-López, A. L., Carvajal-Millán, E., Lizardi-Mendoza, J., López-Franco, Y.,Rascón-Chu, A., Salas-Muñoz, E., et al. (2011). The peroxidase/H2O2 system as afree radical-generating agent for gelling maize bran arabinoxylans: rheologicaland structural Properties. Molecules, 16, 8410e8418.

Mora-Rochin, S., Gutiérrez-Uribe, J. A., Serna-Saldívar, S. O., Sánchez-Peña, P., Reyes-Moreno, C., & Milán-Carrillo, J. (2010). Phenolic content and antioxidant activityof tortillas produced from pigmented maize processed by conventional nix-tamalization or extrusion cooking. Journal of Cereal Science, 52, 502e508.

Niño-Medina, G., Carvajal-Millán, E., Lizardi, J., Rascón-Chu, A., Márquez-Escalante, J.,Gardea, A., et al. (2009). Maize processing wastewater arabinoxylans: gellingcapability and crosslinking content. Food Chemistry, 115, 1286e1290.

Niño-Medina, G., Carvajal-Millán, E., Rascón-Chu, A., & Márquez-Escalante, J. (2010).Ferulated arabinoxylans and arabinoxylans gels: structure, sources and appli-cations. Phytochemistry Reviews, 9, 111e120.

Núñez-Santiago, M. C., Méndez-Montealvo, M. G. C., & Solorza-Feria, J. (2001).Introducción a la reología (1st ed.) (pp. 88e92). D.F: Instituto Politécnico Nacional.

Saeed, F., Pasha, I., Anjum, F. M., & Sultan, M. T. (2011). Arabinoxylans and arabinoga-lactans: a comprehensive treatise. Journal of Food ScienceandNutrition, 51, 467e476.

Saulnier, L., & Thibault, J. F. (1999). Ferulic acid and diferulic acids as components ofsugar-beet pectins as maize bran components of sugar-beet pectins a maizebran heteroxylans. Journal of the Science of Food and Agriculture, 79, 396e402.

Yadav, M. P., Moreau, R. A., & Hicks, K. (2007). Phenolic acids, lipids, and proteinsassociated with purified corn fiber arabinoxylans. Journal of Agricultural andFood Chemistry, 55, 943e947.