7/27/2019 1-s2.0-S0023643813004878-main

1/6

Granola bars prepared with Agave tequilanaingredients: Chemicalcomposition and in vitrostarch hydrolysis

Victor M. Zamora-Gasga a,Luis A. Bello-Prez c, Rosa I. Ortz-Basurto a, Juscelino Tovar b,Sonia G. Syago-Ayerdi a,*a Instituto Tecnolgico de Tepic, Laboratorio Integral de Investigacin en Alimentos, Divisin de Estudios de Posgrado, Av Instituto Tecnolgico No 2595,

Col Lagos del Country, CP 63175 Tepic, Nayarit, Mexicob Functional Food Science Centre, Lund University, Medicon Village, Scheelevgen 2SE-223 81, Swedenc Centro de Desarrollo de Productos Biticos (CEPROBI) del Instituto Politcnico Nacional, Apartado Postal 24, CP 62731 Yautepec, Morelos, Mexico

a r t i c l e i n f o

Article history:

Received 19 July 2013Received in revised form29 November 2013Accepted 10 December 2013

Keywords:

Agave tequilana

FructansDietary berPredicted glycemic indexStarch hydrolysis

a b s t r a c t

The stem ofAgave tequilanais used to obtain: agave syrup (AS) and native agave fructans (NAF). Ground-agave-ber is the by-product from fructans production. These ingredients were used to design a foodingredient: agave dietary ber (ADF), containing NAF (30 g/100 g) as soluble dietary ber (DF) andground-agave-ber (70 g/100 g) as an insoluble DF. The objective of this work was to evaluate the effectof the incorporation ofA. tequilana ingredients (AS, NAF, ADF) on the proximate composition, in vitrostarch hydrolysis (HI) and predicted glycemic index (pGI) of oat-based granola bars. Total DF (82.03 g/100 g) was the main component in ADF, with 22.8 g/100 g soluble DF. Granola bars were prepared bysubstituting honey and wheat our by AS and ADF. A sensory test was used to select the level of sugarsubstitution by NAF, where 62 g NAF/100 g was the preferred one. The effect of each ingredient on thechemical composition was evaluated using a 231 fractional design. Soluble DF in a granola bar con-taining a combination of three agave ingredients (AS, NAF and ADF) was 23.35 g/100 g, with HI and pGIvalues of 74 and 72%, respectively, pointing this product as a moderate GI food.

2013 Elsevier Ltd. All rights reserved.

1. Introduction

Agave tequilanaWeber var.Azul, also known as blue agave, is aplant that grows in arid and semi-arid zones in Mexico. The stem,known as pineappleor head, is mainly used for production oftequila, a widely accepted alcoholic beverage (Narvez-Zapata &Snchez-Teyer, 2010). Currently, the demand of agave heads forTequila production is over one million tons annually but, due to lackof proper planning and control, agave yields are frequently greaterthan demand, resulting in annual losses over 200,000 ton of agave

heads (CRT, 2011). An alternative for the exploitation of this surplusis the use of different ingredients that can be obtained from thisplant. Agave head exhibits an average carbohydrate contentranging between 13 and 17 g/100 g (fresh basis), a fraction con-sisting of mainly fructans (vila-Fernandez et al., 2009).The headisthus used for preparing fructose syrup and agave fructans. Agavefructans are composed by simple sugars and a complex mixture of

fructooligosaccharides. Fructans show b-(2/1) and b-(2/6)linkages, with internal (neoseries fructans) and external (gra-minans fructans) glucose units (Mellado-Mojica & Lpez, 2012).These carbohydrates are considered as soluble dietary ber (DF),since they are resistant to hydrolysis by human digestive enzymesand can be fermented by colonic microbiota producing short chainfatty acids (Lpez, Mancilla-Margalli, & Mendoza-Diaz, 2003). Inaddition, agave fructans show prebiotic potential, increasing Bi-dobacteria and Lactobacilli populations in the large intestine(Gmez, Tuohy, Gibson, Klinder, & Costabile, 2009). Moreover,

agave fructose syrup (commonly known as agave syrup, AS) isobtained from the plant head by acidic hydrolysis of the Agave juiceand it has received attention as an alternative to traditionalsweeteners, such as table sugar (sucrose) and honey (Kango & Jain,2011). In the process of agave fructans extraction, the stem, with anaverage weight of 50 kg per plant, generates a by-product (about30 g/100 g) that is usually discarded despite its high insoluble DFcontent (Iiguez-Covarrubias, Lange, & Rowell, 2001) and potentialhealth benecial effects (Schieber, Stintzing, & Carle, 2001).Nowadays, the search and use of novel DF sources and food in-gredients is a trend especially in those populations where DF intakeis compromised. Hence, the aim of this study was to developed oat

* Corresponding author. Tel.: 52 311 211 94 00x328.E-mail addresses: sonia.sayago@gmail.com, soniagpesayago@yahoo.com.mx

(S.G. Syago-Ayerdi).

Contents lists available atScienceDirect

LWT - Food Science and Technology

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m/ l o c a t e / l w t

0023-6438/$e see front matter 2013 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.lwt.2013.12.016

LWT - Food Science and Technology 56 (2014) 309e314

mailto:sonia.sayago@gmail.commailto:soniagpesayago@yahoo.com.mxhttp://www.sciencedirect.com/science/journal/00236438http://www.elsevier.com/locate/lwthttp://dx.doi.org/10.1016/j.lwt.2013.12.016http://dx.doi.org/10.1016/j.lwt.2013.12.016http://dx.doi.org/10.1016/j.lwt.2013.12.016http://dx.doi.org/10.1016/j.lwt.2013.12.016http://dx.doi.org/10.1016/j.lwt.2013.12.016http://dx.doi.org/10.1016/j.lwt.2013.12.016http://www.elsevier.com/locate/lwthttp://www.sciencedirect.com/science/journal/00236438http://crossmark.crossref.org/dialog/?doi=10.1016/j.lwt.2013.12.016&domain=pdfmailto:soniagpesayago@yahoo.com.mxmailto:sonia.sayago@gmail.com

7/27/2019 1-s2.0-S0023643813004878-main

2/6

granola bars containing A. tequilana ingredients, and to evaluatetheir chemical composition and predicted glycemic index (pGI).

2. Materials and methods

2.1. Agave dietary ber preparation

A local company (Bioagaves de la Costa SA de CV, Tepic, Nayarit,Mexico) provided Agave syrup (AS) and the other agave ingredients(NAF and ground-agave-ber). The industrial process followed toobtain the ingredients can be briey described as follows: thestems fromA. tequilana plants were groundand suspended in waterto obtain a juice (18e22 Brix) that is ltered and claried in a lterpress. The juice is then spray-dried (LPG5 Model, Sinotek, S. A. de C.V. Guadalajara Jalisco, Mxico) with an outlet temperature of 80 C,atomizer speed at 30,000 rpm and 24 m/s air ow in one system, aprocess that yields 145 10 g/kg of a white crystalline powder(native agave fructans, NAF). As by-product, the remainingber inthe stem is used to obtain the ground-agave-ber by washing,drying and grounding the former residue in order to prepare a nepowder that is sieved through a 0.05 mm screen. For the purpose of

the present study, agave dietary ber (ADF) was prepared as a 1:3(g/g) mixture of NAF (soluble dietary ber) and ground-agave-ber(insoluble dietary ber). This mixture provides a SDF/IDF ratioresembling that recommended by international dietary guidelines(Block, 1991).

Chemical composition; Moisture content was determined by agravimetric method, heating 2 g of sample (60 C for 24 h). Ash,protein and fat in ADF were analyzed according toAOAC (1990)methods 923.03, 920.87 and 920.39 respectively. Also, DF wasassessed using the enzymaticegravimetric method described byProsky, Asp, Schweizer, DeVries, and Furda (1988), modied byMaas and Saura-Calixto (1995).

2.2. Granola bars formulation

The ingredients for granola bars were purchased in a local su-permarket, in Tepic, Nayarit State, Mexico. The basic formulationused for preparing oat-based granola bars was as follows: Oatakes, 49 g/100 g (Grupo Industrial Vida, Zapopan, Jalisco, Mxico);soy lecithin, 4 g/100 g (Grupo Pronat, Cd. Mxico, D.F., Mxico);wheat our, 4 g/100 g (Tres Estrellas, Toluca, Estado de Mxico,Mxico); sugar, 18 g/100 g (Tiendas Soriana, Cd. Mxico, D.F.,Mxico); vegetable oil, 14 g/100 g (Aceites, Grasas y Derivados Cd.Mxico, D.F., Mxico); vanilla essence, 1 g/100 g (Molina, ProductosUvavia, S.A. de C.V., Zapopan, Jalisco, Mxico); and honey, 10 g/100 g (VitaReal, Alimentos Naturistas Siglo XXI, S.A. de C.V., Cd.Mxico, D.F., Mxico).

Oat akes were previously roasted at 140

C and mixed withwhole-wheat our. Vegetable oil, honey and soy lecithin wereheated at 90 C in a pan for 2 min. Liquid ingredients were mixedwith the solid ingredients for 5 min. The bars were cut in a rect-angular mold and baked in an oven (Maytac, MER7662WS, USA), at150 C for 15 min. Once baked, granola bars were cooled down toroom temperature and stored in plastic containers with hermeticcaps, until the sensory analysis test were performed.

Control bars were prepared using AS instead of honey as mainsweetener. In the agave ber-containing granola preparations,honey andour were substituted by AS and ADF, respectively,usingthe same proportion prescribed in the basic original formula. Sugarwas substituted at ve different levels (50, 62.5, 75, 87.5 and 100 g/100 g, respectively) by NAF, and the granolas were evaluated in a

sensory test to obtain the optimal substitution level.

2.3. Sensory analysis: sweetness and preference test

Two sensory tests were performed. These tests were applied togranola bars prepared with different NAF contents (50, 62.5, 75,87.5 and 100 g NAF substitution/100 g sugar) with the purpose ofchoosing the best preparation for further analysis. For the sweet-ness test, 11 judges (3 men and 8 women, 23e27 years old) wereselected to determine differences in sweetness intensity betweensamples with ve different levels of sugar substitution with NAF. Aprevious training was conducted using a sequential analysis. Aconsumer panel untrained (n 24, 16 men and 8 women, ages 23e30 years) took part voluntarily in the preference test. The panel waschosen at random from students and personnel from Tepic Tech-nology Institute. Both groups of panelists ranked the samples in ascale from 1 to 5, where 1 was the minimum sweetness or pref-erence level and 5 was the maximum value. Twenty-ve grams ofeach sample, with a rectangular shape, were presented randomly.The tests were performed at 25 C. Data were analyzed with theFriedman Rank Sum Test, using a critical value equal to 21 (n 11)in the sweetness test and a critical value equal to 30 (n 24) in thepreference test. Statistical signicance was determined atp < 0.05(Pedrero & Pangborn, 1989).

2.4. Evaluation of physical properties in granola bars

A fractional factorial 232 design was used to evaluate the effectof including each agave ingredient on the physical properties andchemical composition of the selected granola bar formulation. Thephysical properties were evaluated as follows: samples wereweighed and thickness was measured with a thickness caliper. Acolorimeter (Minolta Chroma Meter CR-300 Series, Osaka, Japan)was used to determine the barssurface color. Color values wererecorded as L* lightness (where 0 black, 100 white), a*(a* redness and a* greenness) and b* (b* yellownessand b* blueness) and compared to a standard white calibrationplate (CR-A44) with a wide-area illumination (measuring area50 mm)/0 C viewing angle. Baking efciency was calculated as theweight loss (g/100 g) before and after baking in granola bars.

After the evaluation of physical properties, the samples weremilled (IKA M20, USA) and sieved using an 800 micron mesh, andplaced in bags with seal, for storage at 20 C until subsequentanalyses.

2.5. Chemical composition in granola bars added with agave

ingredients

Moisture content, ash, protein and fat were analyzed accordingto AOAC (1990) methods 925.10, 923.03, 920.87 and 920.39respectively. Potentially available starch was assessed following the

multienzymatic protocol ofHolm, Bjrck, Drews, and Asp (1986)using Termamyl (Novo A/S, Copenhagen, Denmark) and amylo-glucosidase (Boehringer, Mannheim, Germany).

Dietary ber was analyzed using the enzymaticegravimetricmethod described byProsky et al. (1988), modied byMaas andSaura-Calixto (1995). Total carbohydrates (non-starch poly-saccharides, NSP) in the soluble and insoluble DF fractions weremeasured by Englyst and Cummings (1988) and the remainingresidues were quantied as Klason lignin (KL). Insoluble DF wasquantied as NSP plus KL. Total DF was considered as the sum ofsoluble DF and insoluble DF.

The caloric value was calculated using the factors: protein17 kJ g1 (4 kcal g1), fat 37 kJ g1 (9 kcal g1), carbohydrate17 kJ g1 (4 kcal g1) (FAO/WHO/ONU, 2004) and 6.3 kJ g1

(1.5 kcal g

1

) for DF (Roberfroid, 1999).

V.M. Zamora-Gasga et al. / LWT - Food Science and Technology 56 (2014) 309e314310

7/27/2019 1-s2.0-S0023643813004878-main

3/6

2.6. Starch hydrolysis index in granola bars as eaten(chewing/

dialysis test)

The in vitro rate of starch hydrolysis was assessed with theprotocol developed byGranfeldt, Bjrck, Drews, and Tovar (1992).Samples containing 1 g potentially available starch from the controlgranola bar and granola bars substituted with the agave ingredients(AF, ADF, NAF) were analyzed. Six healthy subjects participated inthe chewing phase of the experiments, which consistedof 15 chewsin 15 s. The chewed material was carefully expectorated into a20 mL beaker containing 0.05 moL/L phosphate buffer adjusted topH 1.5 with HCl, and the mixture was incubated with bovine pepsin(P-7000, Sigma Aldrich, St Louis MO, USA) for 30 min (37 C),neutralized (pH 6.9) and incubated with porcine pancreatic a-amylase (A-6255, Sigma Aldrich) in a dialysis bag (D9652 e30.480 m avg., Sigma Aldrich). The reducing amylolysis productsappearing in the dialysate were measured colorimetrically andexpressed as maltose equivalents. Data were plotted as degree ofhydrolysis versus time curves, and the hydrolysis index (HI) wascalculated as the area under the curve (0e180 min) for the testproduct expressed as percentage of the corresponding area forcommercial white bread, chewed by the same person.

2.7. Statistical analysis

A completely random design with three replicates was used toanalyze the chemical composition and physical properties.Analytical data were expressed as the mean with standard devia-tion, and statistical signicance was determined atp < 0.05. Meanswere compared using Fishers LSD multiple comparisons proce-dure. Statistical analyses wereperformed using SAS version 9.1.3 forWindows (SAS Institute Inc., NC, USA). The average HI was calcu-lated from the six digestions replicates run for each sample, andmeans werecompared by Wilcoxon matched-pair signed-rank test,each person being his own control. The predicted glycemic index(pGI) was calculated from HI values using the empiric formula

proposed byGranfeldt (1994): pGI 0.862 HI 8.198 (r0.985,p < 0.005). The predicted glycemic load (pGL) was calculated bymultiplying pIG of granola bars by the content of available carbo-hydrate of 30 g of product, considered as a portion sized, divided by100 (Foster-Powell, Holt, & Brand-Miller, 2002). Statistical analyseswere performed using Statistic 8.0 Release for Windows (Stat Soft.Inc., Tulsa, OK, USA).

3. Results and discussion

3.1. Chemical composition of agave dietary ber (ADF)

DF was the main component in ADF (Table 1). Soluble DF rep-resented 28 g/100 g of the total DF. Agave fructans are a type of

soluble DF with recognized benecial health properties (Urias-

Silvas et al., 2008). However selective consumption of the solublecomponents; is inconvenient, as they are rapidly fermented in thecolon, leading to abdominal discomfort (Lunn & Buttriss, 2007). Inthis work, a mixture of soluble DF from agave fructans and insol-uble DF obtained from an agave processing by-product, i.e. ground-agave-ber, was used, which may result in betterin vivotolerance.Ground-agave-ber has been reported to consist mainly of non-starch polysaccharides, such as cellulose (42e49 g/100 g), andlignin (16e17 g/100 g) (Iiguez-Covarrubias, Acosta, Martnez, &Gonzlez, 2005; Iiguez-Covarrubias et al., 2001; Kestur et al.,2013). Moreover, the use of the by-product as a source of insol-uble DF could be an alternative to overcome the environmentalproblem that may represent its disposal. ADF shows a greater totalDF content than cereals such as wheat bran (36.5e52.4 g/100 g) andoat bran (18.1e25.2 g/100 g) (Vitaglione, Napolitano, & Fogliano,2008). Other proximate constituents determined in ADF were:ash content, which was lower than that reported for agave bagasseber obtained during production of tequila; protein content washigher than in other commercial bers such as oat (0.8 g/100 g) andwheat (0.4 g/100 g) (Valencia & Romn, 2006). Fat level was lowerthan those reported in cocoa by-products as cocoa husks (2.34 g/100 g), cocoa bean shell (2.02 g/100 g) and cocoa mucilage (1.92 g/

100 g) (Martnez et al., 2012). ADF exhibited low moisture content.All these features in ADF could represent technological advantagesin the development of new ber-rich food products.

3.2. Preference test: sensory analysis

It is well documented that DF plays an important role in diseaseprevention and enhanced health of consumers. Oneway to increaseDF intake is through its incorporation into food commodities, aprocedure that brings the challenge of maintaining adequate sen-sory acceptance. In this study, the granola sample with 100%replacement of sugar by NAF exhibited minimal sweetness (Table 2,

p < 0.05). However, no signicant difference was observed amongtherest of thesamples,despitethe use of a previously trained panel.

According to the preference test, the substitution of sugar withboth 50 and 62 g NAF/100 g resulted in granola bars with thehighest rank sum values (Table 2) with an equivalent level ofpreference (p > 0.05). These two NAF-substituted bars were sta-tistically different from the other samples (p < 0.05). NAF arecharacterized by a neutral and slightly sweet avor, and fructanswith low molecular weight show only 10% relative sweetness vs.sucrose (Yun, 1996). The preparation containing the NAF substitu-tion level of 62.5 g/100 g sugar was selected for subsequent ana-lyses. Thus the inclusion of 10 g NAF and 4 g ADF per 100 g ofgranola is reected in an increase of soluble DF content and a goodoverall perception, combining various sensory parameters, such asrmness, texture and crunchiness, that were not evaluated indi-vidually but are included in the preference test. According to

Foschia, Peressini, Sensidoni, and Brennan (2013), the impact of DFaddition on product quality and sensory acceptance of commoncereal products depends on several factors, such as the type of DFTable 1

Chemical composition of agave dietary ber (ADF) (g/100 g).a

Component

Moisture 2.70 0.04Ash 3.86 0.07Proteinb 2.10 0.16Fat 0.42 0.14Total dietary berc 82.03Soluble dietary ber 22.83 1.22Insoluble dietary ber 59.20 1.89

a Values are mean of three replicates standard deviation. Drymatter basis.

b N 6.25.c

Sum of soluble dietary

ber

insoluble dietary

ber.

Table 2

Sweetness and preference test of granola bars presented in a rectangular shape withweight of 24 g, at 25 C, containing native agave fructans (NAF) as sugar substitute.

Sweetness testc Preference testd

NAF Substitutionb

(g/100 g)50 62.5 75 87.5 100 5 0 62.5 7 5 87.5 1 00

Sum of ranksa 39a 40a 38a 34ab 14b 96a 92a 61b 58b 53b

a Different letters indicate signicant differences.b Substitution levels of sugar by NAF (p < 0.05).c Critical value 21, was taken for 11 judges and 5 samples (p < 0.05).d

Critical value

30, was taken for 24 judges and 5 samples (p 0.05) in the bars thickness,suggesting that the substitution did not affect the physical structureof the product. Regarding the color properties, the addition of ADFresulted in a signicant reduction (up to 7 g/100 g) in lightnessvalues (L*) whose were between 46 and 50 in the various bars. Sun-Waterhouse, Teoh, Massarotto, Wibisono, and Wadhwa (2010)re-ported similar lightness values (40e60) for snacks bars containingapple ber and inulin. Redness (a*) decreased (p < 0.05) in thegranola bar containing NAF. The use of reducing sugars would leadto non-enzymatic (Maillard) browning and/or caramelization re-

actions at elevated temperature (Damodaran,1996), which explainsthe a* value, and the lightly brown color detected in the barsubstituted with NAF. Finally, yellowness (b*) in the bars preparedwith ADF or the blend of the three agave ingredients (AS, ADF, NAF)were reduced up to 12 g/100 g in comparison to the AS-granola bar,this difference that could be due to the ground-agave-ber used inADF, which provided a darker color.

3.4. Chemical composition of granola bars

There were signicant differences in moisture level among thevarious granola products. The substitution by AS and ADF led to thelowest bar, while the bars substituted with NAF and with thecombined three agave ingredients (AS, ADF and NAF) had the

highest moisture values. These differences could be attributed to asynergistic effect of NAF, which are hydrophilic molecules with theability to bind water molecules and may, therefore, inuence waterretention during baking (Capriles, Soares, Pinto e Silva, & Aras,2009). The low water content may favor a longer shelf life ingranola bars, as in other similar products (Agama-Acevedo, Islas-

Hernndez, Pacheco-Vargas, Osorio-Daz, & Bello-Prez, 2012:Sun-Waterhouse et al., 2010; Utrilla-Coello, Agama-Acevedo,Osorio-Daz, Tovar, & Bello-Prez, 2011).

The substitution with agave ingredients did not produce anoticeable change in the ash content of the granola bars, reectingthe low mineral content in these ingredients. Wheat our substi-tution by ADF reduced fat and protein content in the bar products.Many dietary bers are fat and/or oil dispersible, and some of themalso bind oil. Oil binding is in part related to the ber chemicalcomposition, but it is more a function of the ber porous micro-structure than of the intrinsic afnity of the ber molecules for oil.During hydration, water occupies the ber pores, reducing signi-cantly oil-binding and reducing the total fat content in the nalproduct (Tungland & Meyer, 2002).

Protein contents in the granola bars were lower than in barsadded with different types of corn (7e11 g/100 g) (Utrilla-Coelloet al., 2011) or in cookies added with resistant starch (5 g/100 g)(Aparicio-Saguiln et al., 2007), but notably higher than that re-ported for bars added with inulin and apple dietary ber (2e3.5 g/100 g) (Sun-Waterhouse et al., 2010). Protein content in this type ofproduct depends on the formulation employed. Potentially avail-able starch content was higher in AS granola bar than in the othersamples; this may be due to the substitution of wheat our by ADFor the mixture of three agave ingredients.

Total DF content in the bars containing the combined agave in-gredients (AS, NAF and ADF) or NAF alone increased by 67 g/100 gcompared to the AS-and ADF-substituted bars. However, the DF con-tentin ADF bar did not differ(p> 0.05) from thatexhibited by the AS-

containing product. This might be consequence of the rather smallsubstitution (only 4 g/100 g) which might not have been sufcient toproduce a signicant effect. Soluble DF content in the two NAF-containing bars was higher (p < 0.05) than in the other samples (upto72 g/100 g). Thus, in a 30 g portion sizeof granola bar as eaten thecontent of soluble DF would be about 5 g,which allows the product tobeconsideredasahighberfood.Prebioticeffectshavebeenobservedwith an intake of 4e5 g of inulin and oligofructose/day (Roberfroid,2002) a supply that could be easily provided by the NAF-addedgranola bars. Thermal process is a key factor in the use ofber-richingredients by food industry. A study where cereal-based bars wereadded with inulin, either from chicory roots or Jerusalem artichoke(7.7ginulinin36gofbar),showeda97g/100gretentionofinulinafterbakingat 135Cfor18min (Kleessenetal.,2007),whichhighlightsthe

marked resistance of inulin/fructans to drastic processing conditions.

Table 3

Formulations of granola bars according to fractional factorial design (231),substituted with agave syrup (AS), native agave fructans (NAF), agave dietary ber(ADF) and a blend of the three ingredients (AS, NAF, ADF) (g/100 g sample).

Ingredients AS NAF ADF AS, NAF, ADF

Toasted oat akes 49 49 49 49Sugar 18 6.75 18 6.75Vegetal oil 14 14 14 14Soy lecithin 4 4 4 4Vanilla essence 1 1 1 1Wheat whole our 4 4 e eHoney e 10 10 eAS 10 e e 10ADF e e 4 4NAF e 11.25 e 11.25

Table 4

Physical properties of granola bars substituted with agave syrup (AS), native agavefructans (NAF), agavedietaryber(ADF)and blend of the three ingredients (AS, NAF,ADF).a

AS NAF ADF AS, NAF, ADF

Bakingefciency(g/100 g)b

94.97 0.34a 96.58 0.34b 96.58 0.92b 95.58 0.69ab

Thickness (cm) 1.55 0.07a 1.53 0.10a 1.55 0.07a 1.51 0.09aL* 50.46 1.04b 50.68 1.70b 46.83 1.08a 46.20 0.84aa* 5.02 0.55a 4.37 0.41b 5.07 0.49a 5.31 0.99ab* 25.20 1.38b 24.05 0.96b 22.16 0.98a 21.79 1.36a

a Values are mean of three replicates standard deviation, with three repeatedmeasurements. Means in rows marked with different letters are signicantlydifferent (p < 0.05).

b Baking efciency, considered as the weight loss(g/100 g) of the bar after baking.

V.M. Zamora-Gasga et al. / LWT - Food Science and Technology 56 (2014) 309e314312

7/27/2019 1-s2.0-S0023643813004878-main

5/6

In vitrofermentation of Jerusalem artichoke inulin showed improvedpotential prebiotic effect for samples pre-heated at elevated temper-atures (Bhm, Kleessen, & Henle, 2006), a phenomenon that can beexploitedwhendevelopingnovelfructan-basedfunctionalfoods,suchas theagave-containing bars studied here. Some authors attributethisto the D-fructose dianhydrides formed during heating of inulin and

fructooligosaccharides (Minamida et al., 2005; Orban, Patterson,Sutton, & Richards, 1997). The insoluble DF contents in the varioussamples were signicantly different (p

7/27/2019 1-s2.0-S0023643813004878-main

6/6

ber-ingredient prepared from common by-products from the in-dustrial processingofA. tequilana. The mixture shows a good balancebetween soluble and insoluble ber fractions. This study showed thefeasibility of incorporating agave ingredients in the formulation ofoat-based granola bars, reducing sugar the content to 10 g/100 ofproduct and preserving consumer preference. The agave ingredientaddition had marked effects on the physical properties, chemicalcomposition and DF content of the bars, placing them as a high berfood. Also, in addition to such reduced energy and increased solubleDF contents, the decreased predicted Glycemic Load features mayconfer added value to this common type of snack.

Acknowledgments

Zamora-Gasga, VM; acknowledge the fellowship to ConsejoNacional de Ciencia y Tecnologa (CONACYT e Registration number:253795) and Syago-Ayerdi, SG; would also like to acknowledge thenancial support to PROMEP eITTEP-PTC-003.

References

Agama-Acevedo, E., Islas-Hernndez, J. J., Pacheco-Vargas, G., Osorio-Daz, P., &

Bello-Prez, L. A. (2012). Starch digestibility and glycemic index of cookiespartially substituted with unripe banana our. LWTe Food Science and Tech-nology, 46(1), 177e182.

AOAC. (1990).Association of Ofcial Agricultural Chemists. Ofcial methods of analysis(15th ed.).

Aparicio-Saguiln, A., Syago-Ayerdi, S. G., Vargas-Torres, A., Tovar, J., Ascencio-Otero, T. E., & Bello-Prez, L. A. (2007). Slowly digestible cookies prepared fromresistant starch-rich lintnerized banana starch. Journal of Food Composition and

Analysis, 20(3e4), 175e181.vila-Fernndez

, A. N., Rendo

n-Poujol, X., Olvera, C., Gonza

lez, F., Capella, S., Penea-A

lvarez, A., et al. (2009). Enzymatic hydrolysis of fructans in the tequila pro-duction process.Journal of Agricultural and Food Chemistry, 57(12), 5578e5585.

Block, G. (1991). Dietary guidelines and the results of food consumption surveys.The American Journal of Clinical Nutrition, 53(1), 356Se357S.

Bhm, A., Kleessen, B., & Henle, T. (2006). Effect of dry heated inulin on selectedintestinal bacteria. European Food Research and Technology, 222(5), 737e740.

Brennan, M. A., Derbyshire, E., Tiwari, B. K., & Brennan, C. S. (2013). Ready-to-eat snackproducts: the role of extrusion technology in developing consumer acceptable andnutritious snacks. International Journal of FoodScience& Technology, 48(5),893e902.

Capriles, V. D., Soares, R. A. M., Pinto e Silva, M. E. M., & Aras, J. A. G. (2009). Effectof fructans-based fat replacer on chemical composition, starch digestibility andsensory acceptability of corn snacks. International Journal of Food Science &Technology, 44(10), 1895e1901.

Cereser-Camara, V., & Laux, D. (2010). Moisture content in honey determinationwith a shear ultrasonic reectometer.Journal of Food Engineering, 96(1), 93e96.

Clegg, M. E., Pratt, M., Markey, O., Shafat, A., & Henry, C. J. K. (2012). Addition ofdifferent fats to a carbohydrate food: impact on gastric emptying, glycaemicand satiety responses and comparison with in vitro digestion. Food ResearchInternational, 48(1), 91e97.

CRT. (2011). Consejo Regulador del Tequila. Anuario Estadstico del Sistema de Pro-duccin Agave-Tequila. Guadalajara, Jal. Mexico. Retrieved June 3, 2013. Availablehttp://www.crt.org.mx.

Damodaran, S. (1996). Amino acids, peptides and proteins. In O. R. Fennema (Ed.),Qumica de Alimentos(pp. 322e429). New York, USA: Marcel Dekker Inc.

Eelderink, C., Moerdijk-Poortvliet, T. C. W., Wang, H., Schepers, M., Preston, T., Boer, T.,etal. (2012).The glycemic response doesnot reecttheinvivostarchdigestibilityofber-rich wheat productsin healthymen. TheJournal ofNutrition,142(2),258e263.

Englyst, H. N., & Cummings, J. H. (1988). Improved method for the measurement ofdietary bre as nonstarch polysaccharide in plant foods. Association of Ofcial

Analytical Chemists, 71, 808e814.FAO/WHO/ONU. (20 04).Human energy requirement. Report of Joint FAO/WHO/ONU.

Expert Consultation. FAO Food and Nutrition Technical Report Series, Rome 17e24 October 2001.

Foschia, M., Peressini, D., Sensidoni, A., & Brennan, C. S. (2013). The effects of dietarybre addition on the quality of common cereal products. Journal of Cereal Sci-ence, 58(2), 216e227.

Foster-Powell, K., Holt, S. H., & Brand-Miller, J. C. (2002). International table ofglycemic index and glycemic load values: 2002. The American Journal of ClinicalNutrition, 76(1), 5e56.

Gmez, E., Tuohy, K. M., Gibson, G. R., Klinder, A., & Costabile, A. (2009). In vitroevaluation of the fermentation properties and potential prebiotic activity ofAgave fructans. Journal of Applied Microbiology, 108(6), 2114e2121.

Granfeldt, Y.(1994).Foodfactorsaffectingmetabolic responsesto cerealproducts(Doctoraldissertation). Dept. of Applied Nutrition and Food Chemistry, Lund University.

Granfeldt, Y., Bjrck, I., Drews, A., & Tovar, J. (1992). An in vitro method based onchewing to predict metabolic responses to starch in cereal and legumesproducts. European Journal of Clinical Nutrition, 46, 649e660.

Holm, J., Bjrck, I., Drews, A., & Asp, N. G. (1986). A rapid method for the analysis ofstarch.Starch e Strke, 38(7), 224e226.

Iiguez-Covarrubias, G., Acosta, T. N., Martnez, C. L., & Gonzlez, O. (2005). Utilizacinde subproductos e la industria tequilera. Part 7: Compostaje de bagazo de agave yvinzas tequileras. Revista Internacional de Contaminacin Ambiental, 21(2), 37e50.

Iiguez-Covarrubias, G., Lange,S. E., & Rowell, R.M. (2001). Utilization of byproductsfrom the tequila industry: part 1: agave bagasse as a raw material for animal

feeding andberboard production.Bioresource Technology, 77(1), 25e32.Kango, N., & Jain, S. C. (2011). Production and properties of microbial inulinases:

recent advances. Food Biotechnology, 25(3), 165e212.Kestur, G. S., Flores-Sahagun, T. H. S., Dos Santos, L. P., Dos Santos, J., Mazzaro, I., &

Mikowski, A. (2013). Characterization of blue agave bagasse bers of Mexico.Composites Part A: Applied Science and Manufacturing, 45(0), 153e161.

Kleessen, B., Schwarz, S., Boehm, A., Fuhrmann, H., Richter, A., Henle, T., et al.(2007). Jerusalem artichoke and chicory inulin in bakery products affect faecalmicrobiota of healthy volunteers. British Journal of Nutrition, 98, 540e549.

Lpez, M. G., Mancilla-Margalli, N. A., & Mendoza-Diaz, G. (2003). Molecularstructures of fructans from Agave tequilanaWeber var. Azul. Journal of Agricul-tural and Food Chemistry, 51(27), 7835e7840.

Lunn, J., & Buttriss, J. L. (2007). Carbohydrates and dietary bre.Nutrition Bulletin/BNF, 32, 21e64.

Maas, E., & Saura-Calixto, F. (1995). Dietary bre analysis: methodological errorsources. European Journal of Clinical Nutrition, 49(Suppl. 3), S158eS162.

Martnez, R., Torres, P., Meneses, M. A., Figueroa, J. G., Prez-lvarez, J. A., & Viuda-Martos, M. (2012). Chemical, technological and in vitro antioxidant properties ofcocoa (Theobroma cacaoL.) co-products. Food Research International, 49(1), 39e45.

Mellado-Mojica, E., & Lpez, M. G. (2012). Fructan metabolism inA. tequilanaWeberblue variety along its developmental cycle in the eld. Journal of Agriculturaland Food Chemistry, 60(47), 11704e11713.

Minamida, K., Shiga, K., Sujaya, I. N., Sone, T., Yokota, A., Hara, H., et al. (2005).Effects of difructose anhydride III (DFA III) administration on rat intestinalmicrobiota. Journal of Bioscience and Bioengineering, 99(3), 230e236.

Montaez-Soto, J., Venegas-Gonzlez, J., Bernardino-Nicanor, A., & Ramos-Ramrez, E. (2011). Enzymatic production of high fructose syrup from Agavetequilana fructans and its physicochemical characterization. African Journal ofBiotechnology, 10(82), 19137e19143.

Narvez-Zapata, J., & Snchez-Teyer, L. (2010). Agaves as a raw material: recenttechnologies and applications. Recent Patents on Biotechnology, 3(3), 185e191.

Orban, J., Patterson, J., Sutton, A., & Richards, G. (1997). Effect of sucrose thermaloligosaccharide caramel, dietary vitamin-mineral level, and brooding temper-ature on growth and intestinal bacterial populations of broiler chickens. PoultryScience, 76(3), 482e490.

Pedrero, D. F., & Pangborn, R. M. (1989). Evaluacin Sensorial de los Alimentos.Mtodos Analticos. Mxico, D. F.: Alambra.

Ponce, S. J. A., Macas, B. E. R., Soltero, A. J. F., Fernndez, E. V. V., Ziga, P. V., &Escalona, B. H. B. (2008). Physicalechemical and non-linear rheological prop-erties of aqueous solutions of agave fructans. e-Gnosis, 6, 1e23. Retrieved on

July 18, 2013. Availablehttp://www.redalyc.org/articulo.oa?id73011197008.Prosky, L.,Asp, N. G.,Schweizer, T.F., DeVries, J. W., & Furda, I. (1988). Determination of

insoluble,soluble,andtotaldietary berinfoodsandfoodproducts:interlaboratorystudy.Journal eAssociation of Ofcial Analytical Chemists, 71(5), 1017e1023.

Roberfroid, M. (1999). Caloric value of inulin and oligofructose. The Journal ofNutrition, 129(7), 1436Se1437S.

Roberfroid, M. (2002). Functional foods: concepts and application to inulin andoligofructose. British Journal of Nutrition, 87(Suppl. 2), S139eS143.

Schieber, A., Stintzing, F. C., & Carle, R. (2001). By-products of plant food processingas a source of functional compounds d recent developments. Trends in FoodScience & Technology, 12(11), 401e413.

Sun-Waterhouse, D., Teoh, A., Massarotto, C., Wibisono, R., & Wadhwa, S. (2010).Comparative analysis of fruit-based functional snack bars. Food Chemistry,119(4), 1369e1379.

Tungland, B., & Meyer, D. (2002). Nondigestible oligo-and polysaccharides (dietaryber): their physiology and role in human health and food. Comprehensive

Reviews in Food Science and Food Safety, 1(3), 90e109.Urias-Silvas, J. E., Cani, P. D., Delmee, E., Neyrinck, A., Lopez, M. G., & Delzenne, N. M.

(2008). Physiological effects of dietary fructans extracted from Agave tequilanaGto. and Dasylirion spp. [Research Support, Non-U.S. Govt]. British Journal ofNutrition, 99(2), 254e261.

Utrilla-Coello, R. G., Agama-Acevedo, E., Osorio-Daz, P., Tovar, J., & Bello-Prez, L. A.(2011). Composition and starch digestibility of whole grain bars containingmaize or unripe banana ours.Starche Strke, 63(7), 416e423.

Valencia, G. F. E., & Romn, M. M. O. (2006). Caracterizacion sicoqumica y fun-cional de tres concentrados comerciales de bra dietaria. Revista de la Facultadde Quimica Farmaceutica, Universidad de Anioquia, 13, 54e60.

Vitaglione, P., Napolitano, A., & Fogliano, V. (2008). Cereal dietary bre: a naturalfunctional ingredient to deliver phenolic compounds into the gut. Trends inFood Science & Technology, 19(9), 451e463.

Yun, J. W. (1996). Fructooligosaccharidesdoccurrence, preparation, and application.Enzyme and Microbial Technology, 19(2), 107e117.

V.M. Zamora-Gasga et al. / LWT - Food Science and Technology 56 (2014) 309e314314

http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref5http://refhub.elsevier.com/S0023-6438(13)00487-8/sref5http://refhub.elsevier.com/S0023-6438(13)00487-8/sref5http://refhub.elsevier.com/S0023-6438(13)00487-8/sref5http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://www.crt.org.mx/http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref19http://refhub.elsevier.com/S0023-6438(13)00487-8/sref19http://refhub.elsevier.com/S0023-6438(13)00487-8/sref19http://refhub.elsevier.com/S0023-6438(13)00487-8/sref19http://refhub.elsevier.com/S0023-6438(13)00487-8/sref19http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref36http://refhub.elsevier.com/S0023-6438(13)00487-8/sref36http://refhub.elsevier.com/S0023-6438(13)00487-8/sref36http://refhub.elsevier.com/S0023-6438(13)00487-8/sref36http://www.redalyc.org/articulo.oa?id=73011197008http://www.redalyc.org/articulo.oa?id=73011197008http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref48http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref47http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref46http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref45http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref44http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref43http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref42http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref41http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref40http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref39http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://refhub.elsevier.com/S0023-6438(13)00487-8/sref38http://www.redalyc.org/articulo.oa?id=73011197008http://www.redalyc.org/articulo.oa?id=73011197008http://refhub.elsevier.com/S0023-6438(13)00487-8/sref36http://refhub.elsevier.com/S0023-6438(13)00487-8/sref36http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref35http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref34http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref33http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref32http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref31http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref30http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref29http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref28http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref27http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref26http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref25http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref24http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref23http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref22http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref21http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref20http://refhub.elsevier.com/S0023-6438(13)00487-8/sref19http://refhub.elsevier.com/S0023-6438(13)00487-8/sref19http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref18http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref17http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref16http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref15http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref14http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref13http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://refhub.elsevier.com/S0023-6438(13)00487-8/sref12http://www.crt.org.mx/http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref10http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref9http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref8http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref7http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref6http://refhub.elsevier.com/S0023-6438(13)00487-8/sref5http://refhub.elsevier.com/S0023-6438(13)00487-8/sref5http://refhub.elsevier.com/S0023-6438(13)00487-8/sref5http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref4http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref3http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref2http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1http://refhub.elsevier.com/S0023-6438(13)00487-8/sref1