Eur Food Res Technol (2010) 230:437445DOI 10.1007/s00217-009-1184-zORIGINAL PAPER

Baking properties and microstructure of pseudocereal Xours in gluten-free bread formulations

Laura Alvarez-Jubete Mark Auty Elke K. Arendt Eimear Gallagher

Received: 30 June 2009 / Revised: 22 September 2009 / Accepted: 3 November 2009 / Published online: 25 November 2009 Springer-Verlag 2009

Abstract In the present study, the baking properties ofthe pseudocereals amaranth, quinoa and buckwheat aspotential healthy and high-quality ingredients in gluten-freebreads were investigated. Scanning electron micrographswere taken of each of the Xours. The pasting properties ofthese Xours were assessed using a rapid visco analyser.Standard baking tests and texture proWle analysis wereperformed on the gluten-free control and pseudocereal-containing gluten-free breads. Confocal laser scanningmicroscopy (CLSM) images were also obtained from thebaked breads and digital image analysis was conducted onthe bread slices. Bread volumes were found to signiWcantlyincrease for the buckwheat and quinoa breads in compari-son with the control. In addition, the pseudocereal-contain-ing breads were characterised by a signiWcantly softercrumb texture eVect that was attributed to the presence ofnatural emulsiWers in the pseudocereal Xours and conWrmedby the confocal images. No signiWcant diVerences wereobtained in the acceptability of the pseudocereal-containinggluten-free breads in comparison with the control.

Keywords Pseudocereals Gluten free Bread Microscopy Baking properties Pasting properties

Introduction

To date, the only treatment available for celiac disease is astrict lifelong adhesion to a gluten-free diet [1]. Therefore,celiac patients must avoid the consumption of gluten-con-taining foods. However, this may prove a diYcult and over-whelming task for the celiac patients as the majority of thecereal-based foods available in the market (such as pasta,baked products, snacks and breakfast cereals) are preparedwith gluten-containing grains, such as wheat [2]. Althoughgluten-free alternatives are readily available, Wnding good-quality gluten-free products has been reported as a majorissue for celiac patients who are trying to adhere to a glu-ten-free diet [3, 4].

Despite recent advances in the formulation of high-quality gluten-free products, the replacement of gluten incereal-based products, such as bread, biscuit, cake andpasta, still represents a signiWcant technological challenge[5]. The formulation of gluten-free breads possibly repre-sents the greatest challenge, due to the fundamental roleof gluten in breadmaking [6]. Gluten is an essential struc-ture-building protein that provides viscoelasticity to thedough, good gas-holding ability and good crumb structureof the resulting baked product [5]. Some of the mostimportant approaches developed to date to mimic theproperties of gluten in gluten-free bakery productsinvolve the use of gums, hydrocolloids and protein-basedingredients [6].

Considerably, fewer studies have been dedicated toimproving the nutritional quality of gluten-free products.Gluten-free cereal foods are frequently made using reWnedgluten-free Xour or starch and are generally not enriched orfortiWed [7]. As a result, many gluten-free cereal foods donot contain the same levels of B-vitamins, iron and Wbre astheir gluten-containing counterparts [7, 8]. A need to

L. Alvarez-Jubete E. Gallagher (&)Ashtown Food Research Centre, Teagasc, Ashtown, Dublin 15, Irelande-mail: Eimear.Gallagher@teagasc.ie

L. Alvarez-Jubete E. K. ArendtDepartment of Food and Nutritional Sciences, National University of Ireland, Cork, Ireland

M. AutyNational Food Imaging Centre, Moorepark Food Research Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland123

438 Eur Food Res Technol (2010) 230:437445improve their nutritional quality has been raised by manymedical and nutritional experts [2, 9].

Several gluten-free grains exist, such as the pseudocere-als amaranth, quinoa and buckwheat. These seeds are alsocharacterised by an excellent nutrient proWle. Besides beingimportant energy sources due to their starch content, ama-ranth, quinoa and buckwheat provide good-quality protein,dietary Wbre and lipids rich in unsaturated fats [10]. More-over, they contain adequate levels of important micronutri-ents, such as minerals and vitamins and signiWcant amountsof other bioactive components, such as saponins, phytoster-ols, squalene, fagopyritols and polyphenols [1114]. A recenttrend by researchers has focused on their use in the formu-lation of high-quality healthy gluten-free products, such asbread and pasta.

In a series of recent studies, the nutritional propertiesand baking characteristics of amaranth, quinoa and buck-wheat have been assessed [10, 12, 15]. The authors foundthat the replacement of potato starch with a pseudocerealXour resulted in gluten-free breads with an increased con-tent of important nutrients, such as protein, Wbre, calcium,iron and vitamin E. The resulting breads also had a signiW-cantly higher content of polyphenol compounds and theirin vitro antioxidant activity was increased.

In the present study, technological aspects (i.e. batter/dough and baking properties) related to the application ofthe pseudocereals as ingredients in the production of glu-ten-free breads were evaluated.

Materials and methods

Bread ingredients

Amaranth Xour (Ziegler & Co., Wunsiedel, Germany), qui-noa Xour (Ziegler & Co., Wunsiedel, Germany), rice Xour(S&B Herba, Orpington, Kent, UK), potato starch (HealyChemicals Ltd, Dublin, Ireland), wheat Xour (OdlumGroup, Dublin, Ireland), sunXower oil (Flora, Liverpool,UK), xanthan gum (All In All Ingredients, Dublin, Ireland),fresh yeast (Yeast Product, Dublin, Ireland), salt (ImeosEnterprises, Runcorn, Cheshire, UK) and caster cane sugar(Tate & Lyle, London, UK) were the materials used in thestudy.

Preparation of breads

The diVerent bread formulations are presented in Table 1.The amount of water used in the control and in each of

the pseudocereal-containing breads was kept the same; theonly diVerence in the formulation of the breads was thetype of Xour used as a composite with rice Xour. The glu-ten-free batter was prepared as follows: dry ingredients

were mixed together for 1 min using an A120 Hobart mixer(Hobart Food Equipment, Sydney, Australia) at speed 1,yeast was dissolved in the water and added to the dry ingre-dients together with the oil and the batter formed wasmixed for a further minute. After scraping the base of thebowl, the batter was further mixed for 2 min at speed 2. Thebatter was then scaled into baking tins (400 g) and placed ina proofer (Koma, Roermond, The Netherlands) for 30 minat 35 C and 80% relative humidity. The loaves were bakedin a deck oven (Tom Chandley Ovens, Manchester, UK) at220225 C for 25 min. They were then cooled to roomtemperature and stored in polyethylene bags. Six loaveswere produced per bake and the preparation of the breadswas done in triplicate (i.e. 3 bakes per each type of bread).

Flour pasting properties

The pasting properties of the Xours and starches were eval-uated using a Rapid Visco Analyser (RVA, Newport Scien-tiWc Pty. Ltd, Warriewood, Australia). The method usedwas the RVA General Pasting Method (Newport ScientiWcPty. Ltd, 1998).

Bread evaluation

Loaf volume was measured using a volume meter (TexVolBVM-L370, Sweden). Loaf weight was recorded and loafspeciWc volume (ml/g) calculated. Bake loss deWned as theamount of water and organic material (sugars fermentedand released as CO2) lost during baking was also calculated([weight of the loaf before baking weight of the loaf afterbaking and cooling]/[weight of the loaf before baking] 100).Moisture was measured following a procedure based on theICC method 110.1 [16] using a Brabender moisture oven(Brabender, Duisberg, Germany).

Table 1 Bread formulations

Ingredient (% Xour/starch base)

Gluten-free control (GFC)

Amaranth (A)

Quinoa (Q)

Buckwheat (B)

Rice Xour 50 50 50 50Potato starch 50 Amaranth Xour 50 Quinoa Xour 50 Buckwheat Xour 50Yeast 3 3 3 3Sugar 3 3 3 3Salt 2 2 2 2Xanthan gum 0.5 0.5 0.5 0.5SunXower oil 6 6 6 6Water 87 87 87 87123

Eur Food Res Technol (2010) 230:437445 439Crust and crumb colour were measured using a MinoltaChromameter (Minolta CR-100, Osaka, Japan) and resultswere expressed using the L*, a*, b* colour scale. Crumbstructure of the loaves was evaluated using the C-CellBread Imaging System (Calibre Control International Ltd.,UK). The procedure followed in this study consists of thestandardised procedure described by the C-Cell BreadImaging System manufacturer (Calibre Control Interna-tional Ltd., UK). Crumb texture was assessed by conduct-ing a texture proWle analysis (TPA) using a texture analyser(TA-XT2i, Stable Micro Systems, Surrey, UK) equippedwith a 25 Kg load cell and a 36 mm aluminium cylindricalprobe. Pre-test, test and post-test speed were 2, 1 and 5 mm/s, respectively, and compression was set at 40%. All breadevaluation analysis were conducted 24 h after baking (day1) and moisture and TPA analysis were repeated 72 and120 h after baking (days 3 and 5, respectively).

Scanning electron microscopy (SEM)

Flour samples were sprinkled onto double-sided carbontape Wxed to an aluminium specimen stub and examinedunder high vacuum in a Zeiss Aupra 40VP Weld emissionscanning electron microscope (Carl Zeiss SMT, Cam-bridge, UK). Secondary electron images were acquired atan accelerating voltage of 1 kV.

Confocal laser scanning microscopy (CLSM)

Bread samples approximately 5 5 3 mm thick were cutwith a razor blade, placed on a microscope slide and 50 mlof aqueous Nile Blue (0.1% w/w) added to the surface.A coverslip was placed on top and the samples wereimaged in a Lecia SP5 confocal scanning laser microscope.Dual channel images were acquired with a 63 (1.4 NA)objective, using 488 nm argon ion laser excitation to imagefat (pseuodocoloured green) and 633 nm helium neon laserexcitation to reveal protein (pseudocoloured bright red) andgelatinised starch (pseudocoloured dull red). Images,512 512 pixels, 8 bit depth were acquired.

Sensory analysis

Sensory analysis was conducted on all the breads tested bya panel consisting in 17 non-celiac consumers. Panellistswere asked to assess the breads for acceptability, and tomark a 6 cm line (0 = unacceptable, 6 = very acceptable) inaccordance with their opinion.

Statistical analysis

Results were analysed using the statistics toolbox ofthe software Matlab 7.6 R2008a (Mathworks, Natick,

Massachusetts, US). Data were analysed using analysis ofvariance (ANOVA) and the mean were separated by theTukeyKramer test. DiVerences of p < 0.05 were consid-ered signiWcant.

Results

Scanning electron microscopy of the Xours

SigniWcant diVerences can be observed in the scanningelectron micrographs of the pseudocereal Xours, rice Xour,wheat Xour and potato starch (Fig. 1). In particular, the sizeof the Xour particles seems to diVer considerably among theXours under study. Smallest particle size can be observed inpotato starch and wheat Xour, followed by rice, buckwheat,amaranth and quinoa Xours. Also, considerable diVerencescan be observed in the size and shape of the starch granules.The size of the starch granules in amaranth and quinoaXours is signiWcantly smaller ( buckwheat > quinoa > amaranth. Breakdown was sig-niWcantly lower for the pseudocereal Xours compared withrice Xour, which suggests an increased ability of the pseud-ocereals to withstand heating and shear stress. Highest Wnalviscosity was observed for the rice and buckwheat Xours, fol-lowed by amaranth and quinoa (p < 0.05). Similarly, setbackwas highest for rice Xour followed by buckwheat, amaranthand quinoa Xours (p < 0.05). Final viscosity is an importantindicator of the strength of the gel formed upon cooling, andrepresents an important quality parameter. These Wndings arein agreement with previously published studies [1820].

The pasting proWles obtained in the present study for thepseudocereal Xours are consistent with previously reported123

440 Eur Food Res Technol (2010) 230:437445levels of amylose in these Xours, and with the small size oftheir starch granules (see previous section). The amylosecontent of amaranth and quinoa starch is much lower thanthat found in other cereals [21]. In the case of quinoa starch,considerable variability exists within the literature, with

values ranging from 3.5 to 19.6% for quinoa starch [18, 19,22]. The amylose content in amaranth seeds has beenreported to be lower than 8% [19, 23]. Contrarily, the con-tent of buckwheat has been reported to be as high as 47%[20], although similar values to those found in other com-mon cereals (2526%) have also been reported [24].

Bread evaluation

Loaf volume, bake loss and crust/crumb colour

The results for the loaf volume, bake loss (%) and colour ofthe baked breads are presented in Table 3. The replacementof potato starch by each of the pseudocereal Xours had avariable eVect on loaf volume. Loaf volumes wereincreased (p < 0.05) for buckwheat (1.63 ml/g) and quinoa(1.4 ml/g) breads in comparison with the control (1.3 ml/g).However, no diVerence in volume was found between thecontrol breads and those containing amaranth. Bake lossdiVered slightly between the gluten-free control and thepseudocereal-containing gluten-free breads; however, thediVerences were not signiWcant.

In relation to the crust colour of the baked breads, thepseudocereal-containing gluten-free breads were signiW-cantly darker (lower L* values) compared with the gluten-free control. The darkening of the crust colour brought

Fig. 1 Scanning electron micrographs of amaranth, quinoa, buckwheat and rice Xour, potato starch, and wheat Xour. Scale bars row a 100 m;b 20 m; c 2 m

Fig. 2 Pasting proWle of amaranth, quinoa, buckwheat and rice Xour,and potato starch

Table 2 Pasting properties of amaranth, quinoa, buckwheat and rice Xour, and potato starch

PV peak viscosity, TV trough viscosity, BD breakdown (PV TV), FV Wnal viscosity, SB setback (FV TV), Ptime (min), peak time

PV TV BD FV SB Ptime (min)

Amaranth 273.0 2.3 a 225.5 1.7 a 47.5 0.6 a 321.6 2.5 a 96.0 0.8 a 5.7 0.0 aQuinoa 288.0 1.9 b 293.4 1.2 b 5.4 0.7 b 191.8 1.8 b 101.6 0.5 b 7.0 0.0 bBuckwheat 341.4 10.6 c 321.0 6.9 c 19.9 3.2 c 606.5 5.7 c 285.1 1.6 c 6.4 0.1 cRice Xour 429.6 0.1 d 303.1 0.6 d 126.5 0.4 d 599.0 4.6 c 298 2.1 d 5.5 0.0 dPotato starch 479.2 1.8 e 174.9 0.2 e 304.2 1.5 e 201.7 1.2 d 26.7 1.0 e 3.4 0.0 e123

Eur Food Res Technol (2010) 230:437445 441about by the replacement of potato starch by a pseudocerealXour is desirable as gluten-free breads tend to have a lightercrust colour than white wheat breads which sometimesappear artiWcial [25].

Crumb colour (L*/b*) (white/yellow ratio) was alsoinXuenced and the pseudocereal-containing gluten-freebreads were characterised by a signiWcantly darker crumbcolour in comparison with the control.

Digital image analysis

The results for the crumb grain analysis of the baked breadsare summarised in Table 4, and the images obtained arepresented in Fig. 3.

Crumb structure diVered signiWcantly in terms of num-ber of cells, cell volume and wall thickness. Crumb grainrepresents an important attribute when deWning bread qual-ity [26]. In the present study, largest number of cells was

for buckwheat bread followed by quinoa, GFC and ama-ranth breads. Smallest cell volume was found in gluten-freecontrol bread, followed by quinoa, amaranth and buck-wheat breads. Cell wall was thinnest in quinoa bread andincreased subsequently in the order quinoa < gluten-freecontrol < buckwheat < amaranth.

Texture proWle analysis (TPA) of bread crumb

The results for the TPA analysis of the baked breads, aswell as their moisture content, are presented in Fig. 4.

All the pseudocereal-containing gluten-free breads had asofter crumb in comparison with the gluten-free control,with amaranth bread having the softest crumb (p < 0.05)over the entire testing period. Overall, a similar trend wasfound in crumb cohesiveness, where all of the pseudoce-real-containing gluten-free breads had a more cohesivecrumb in comparison with the control (p < 0.05). Again,most cohesive crumb was detected in amaranth bread(p < 0.05). Also, all the pseudocereal-containing gluten-free breads had signiWcantly higher crumb springiness incomparison with the control (p < 0.05). Despite the diVer-ences observed in crumb texture, no signiWcant diVerenceswere recorded in the moisture content of the bread samples.No studies could be found in the literature to with comparethe TPA results obtained in the present study. Previouslypublished studies on the baking properties of the pseudoce-reals focused on their impact on bread volume and sensoryanalysis when added at diVerent levels as composites with

Table 3 SpeciWc volume (ml/g), bake loss (%), crust L* and crumb L*/b* of the baked breads

Mean value of three replicates SD. Mean values followed by the same letter are not statistically diVerent (p < 0.05)

Bread SpeciWc volume (ml/g) Bake loss (%) Crust L* Crumb L*/b*

Amaranth 1.31 0.03 a 9.0 0.5 a 56.0 1.4 a 3.9 0.1 aQuinoa 1.40 0.02 b 9.1 0.4 a 52.7 2.7 a 4.1 0.1 aBuckwheat 1.63 0.05 c 9.0 0.3 a 51.4 0.9 a 5.6 0.3 bGluten-free C 1.29 0.03 a 9.4 0.4 a 69.7 1.4 b 6.4 0.4 c

Fig. 3 Raw (a) and cell (b) images of amaranth, quinoa, buckwheat and gluten-free control breads

Table 4 Crumb structure (digital image analysis) of amaranth, qui-noa, buckwheat and gluten-free control breads

Bread Number of cells Wall thickness Cell volume

Amaranth 2,589 145 a 0.46 0.01 a 21.2 1.5 aQuinoa 3,176 334 b, c 0.42 0.02 b 18.7 2.7 a, cBuckwheat 3,340 87 b 0.44 0.00 b 22.9 0.7 bGluten-free

control2,992 128 c 0.43 0.01 b 17.9 2.0 c123

442 Eur Food Res Technol (2010) 230:437445wheat Xour, and did not measure their impact on the textureproWle of the resulting breads [2730].

The eVect of storage time (120 h) on crumb structurewas also investigated (Fig. 4). Overall, crumb hardnessincreased with storage time. In the case of gluten-free con-trol, amaranth and quinoa breads, the increase in crumbhardness with storage time was not signiWcant. For buck-wheat bread, the increase in crumb hardness was only sig-niWcant after 120 h. In addition, crumb cohesiveness wasfound to decrease with storage time for all bread samplesapart from those containing amaranth. A similar trend wasidentiWed for crumb springiness and, although values forthis parameter were found to decrease with storage time,these diVerences were only signiWcant in the gluten-freecontrol and quinoa breads. Also no signiWcant diVerenceswere recorded in the moisture content of the pseudocereal-containing gluten-free breads during the storage period,with the exception of buckwheat bread, the moisture con-tent of which decreased signiWcantly after 120 h. Theseresults suggest that the pseudocereal-containing gluten-freeproducts may be used in the production of gluten-freebreads with a softer crumb structure. This is a desirablecharacteristic as gluten-free breads are often characterisedby a hard texture [6]. Also the increased cohesiveness andspringiness found in the pseudocereal-containing gluten-free breads can be considered beneWcial, as gluten-freebreads are often characterised by a crumbly, brittle texture[31].

Confocal laser scanning microscopy (CLSM)

The images obtained by confocal laser scanning micros-copy of the bread samples are presented in Fig. 5. Asexpected, signiWcant variation was observed between thediVerent breads. Starch gelatinisation appears to haveoccurred to a greater degree in the gluten-free control breadcompared with the pseudocereal-containing gluten-freebreads, with starch granules fusing together and losing theiroriginal structure. Partial gelatinisation seems to haveoccurred in the pseudocereal-containing gluten-free breads,and as a result, a greater number of starch granules haveretained their integrity. A more homogenous structure isapparent for the pseudocereal-containing gluten-freebreads, with less gas voids and a more even distribution offat, protein and starch. Also, the images reveal the impor-tance of the fat globules in forming complexes with starchgranules and/or stabilising gas cells. This eVect appearsparticularly more predominant in the pseudocereal-contain-ing gluten-free breads in comparison with the gluten-freecontrol.

Sensory analysis

The acceptability scores of the baked breads as determinedby the taste panellists are displayed in Fig. 6. No signiWcantdiVerences were observed in the acceptability of the bakedbreads, showing that pseudocereal Xours may be introduced

Fig. 4 Moisture and TPA proWle of the breads after 24, 72 and 120 h post-baking: (a) crumb hardness; (b) crumb cohesiveness; (c) crumb spring-iness; (d) moisture (%). Mean value of three replicates SD

a

0

1000

2000

3000

4000

5000

6000

Amaranth Quinoa Buckwheat GFC

Crum

b ha

rdne

ss (g

)

24 h72 h120 h

b

00.050.1

0.150.2

0.250.3

0.350.4

0.45

Amaranth Quinoa Buckwheat GFC

Crum

b co

hesi

vene

ss

24 h72 h120 h

c

00.10.20.30.40.50.60.70.80.9

1

Amaranth Quinoa Buckwheat GFC

Crum

b sp

ringi

ness

24 h72 h120 h

d

45

45.5

46

46.5

47

47.5

48

48.5

Amaranth Quinoa Buckwheat GFCM

oist

ure

(%)

24 h72 h120 h123

Eur Food Res Technol (2010) 230:437445 443into a gluten-free bread formulation to enhance crumb soft-ness and cohesiveness and without adversely aVecting thesensory properties of the loaves.

Discussion

Some of the more important properties when assessing thequality of baked breads are loaf volume and crumb texture.This study showed how bread volume can be signiWcantlyincreased following the incorporation of pseudocerealXours, such as quinoa and buckwheat. The volume of bread

depends on a number of factors, such as viscosity of thebatters, amylose/amylopectin ratio, the presence ofsurface-active components and/or the occurrence of proteinaggregation upon heating [32]. In gluten-free breads, theviscosity of the batters prior to starch gelatinisation is cru-cial to prevent the Xour particles from settling and gas cellsfrom rising and thus, maintain a homogenous system dur-ing prooWng and baking until starch gelatinisation [32].Therefore, factors, such as peak viscosity of the battersseem to have implications in relation to the Wnal quality ofthe resultant baked bread. In the present study, bread vol-ume of the pseudocereal-containing gluten-free breads wasfound to increase accordingly with peak viscosity of thepseudocereal Xour as measured by the rapid visco analyser.Also, the amylose/amylopectin ratio is a crucial factordetermining bread volume and crumb structure as amylosecontributes signiWcantly to crumb setting due to its quickretrogradation rate [32]. As discussed in the previous sec-tion, the amylose content in amaranth and quinoa Xours islower than in wheat, whereas buckwheat has higher levelsof amylose than those found in cereals. These Wndings areconsistent with the obtained results in this study: bread vol-umes and crumb structure were found to improve accordingto the previously reported amylose contents of the pseud-ocereal Xours.

The lipid content and composition in amaranth, quinoaand buckwheat seeds may also have implications in relationwith functionality during bread making. It has been shownthat polar lipids naturally present in cereals may contribute

Fig. 5 Confocal laser scanning micrographs of gluten-free control, amaranth, quinoa and buckwheat breads. Scale bars row a 0250 m; b 0250 m; c 050 m

Fig. 6 Acceptability scores of baked breads

0

1

2

3

4

5

6

Amaranth Quinoa Buckwheat GFC123

444 Eur Food Res Technol (2010) 230:437445towards the stabilisation of gas bubbles during bread mak-ing [32, 33]. The confocal laser scanning micrographs ofthe baked breads obtained in the present study show thatlipids in amaranth, quinoa and buckwheat may act as sur-face-active agents and thus contribute to gas cell stabilisa-tion prior to starch gelatinisation. This eVect wasparticularly relevant in quinoa breads. However, no sucheVect was observed in the gluten-free control bread. Lipidcontent in amaranth and quinoa seeds has been reported asbeing 23 times higher than that in buckwheat or in com-mon cereals, such as wheat [10]. The content of polar lipidsin quinoa seeds is very high and represents approximately25% of total lipids [34]. The polar lipid content in amaranthseeds has been reported to be approximately 10% of totallipids [35], whereas in buckwheat it ranges between 13.5and 15.5% total lipids [36]. Thus, the high level of polarlipids in pseudocereal seeds, and in particular in quinoaseeds, may have functionality as gas cell stabilising agentsduring bread making.

Also, the high levels of fats present in amaranth and qui-noa Xours may have implications in relation with bothcrumb structure and crumb texture. The use of emulsiWersin baking has been shown to have a softening eVect onbread crumb [37]. Fatty acids from lipid, such as monogly-cerides can form complexes with amylose, thus limitingstarch swelling during baking and leaching of amylose intosolution [37, 38]. As a result, fewer entanglements betweenstarch granules and amylose in solution take place, leadingto breads with a softer crumb structure [32]. Monoglyce-rides in amaranth Xour have been reported to be in therange 3.03.8% total lipid content [35]. In quinoa seedsmonoglyceride levels are lower (approximately 2%) but thelevels of free fatty acids are high (19% total lipid content)[34]. As previously seen, the confocal laser scanningmicrographs of the pseudocereal-containing baked breadsshowed fat molecules surrounding starch compounds andpossibly, forming complexes with starch molecules. ThiseVect thus, supports the hypothesis that the emulsiWers nat-urally present in the pseudocereal Xours may have a posi-tive eVect, resulting in breads with a softer crumb.However, as previously discussed, amylose is necessary forgood crumb structure, and the presence of emulsiWers maythus have a weakening eVect on crumb structure. The lowlevels of amylose in amaranth and quinoa Xour, as well asthe high fat content characteristic of these Xours may beresponsible for their soft texture, but also for their relativelyweak crumb structure when processed into breads, in com-parison with buckwheat Xour.

Other aspects in relation to the functionality of theseXours in gluten-free systems remain to be investigated, suchas the application of hydrocolloids other than xanthan gum.For example, hydroxypropylmethylcellulose (HPMC) is ahydrocolloid with surface-active properties, thus its use in

the formulation of pseudocereal-containing gluten-freebreads may result in breads with improved crumb structureand volume. Also, the pseudocereal-containing breads maybeneWt from higher water levels, especially in the case ofbuckwheat and quinoa breads, due to the higher water bind-ing capacity upon heating of buckwheat and quinoa Xours,as seen in their respective pasting proWles. In addition, ama-ranth and quinoa breads may beneWt from the presence ascomposites of gluten-free Xours with high amylose content,such as buckwheat Xour, to compensate for their intrinsiclow amylose content. Finally, the role of natural emulsiWerspresent in the pseudocereal Xours may have potential in theproduction of gluten-free breads characterised by animproved crumb texture.

The production of high-quality gluten-free breads con-taining pseudocereal Xours would represent a signiWcantstep towards ensuring an adequate intake of nutrients inpeople with celiac disease.

Conclusions

The gluten-free breads containing buckwheat or quinoa Xourhad a signiWcantly higher volume in comparison with the glu-ten-free control. All the pseudocereal-containing gluten-freebreads were characterised by a signiWcantly softer crumb.This eVect was attributed to the presence of natural emulsiW-ers in the pseudocereal Xours and was conWrmed by confocallaser scanning microscopy. Results from the sensory panelshowed that pseudocereal Xours may be introduced into agluten-free bread formulation without adversely aVecting thesensory properties of the loaves. The pseudocereal Xours rep-resent feasible ingredients in the manufacture of good-qual-ity, healthy gluten-free breads.

Acknowledgment The present study is Wnancially supported byEnterprise Ireland.

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Baking properties and microstructure of pseudocereal Xours in gluten-free bread formulationsAbstractIntroductionMaterials and methodsBread ingredientsPreparation of breadsFlour pasting propertiesBread evaluationScanning electron microscopy (SEM)Confocal laser scanning microscopy (CLSM)Sensory analysisStatistical analysis

ResultsScanning electron microscopy of the XoursPasting properties of the XoursBread evaluationLoaf volume, bake loss and crust/crumb colourDigital image analysisTexture proWle analysis (TPA) of bread crumb

Confocal laser scanning microscopy (CLSM)Sensory analysis

DiscussionConclusionsReferences

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