Journal of Food Engineering 105 (2011) 493–502

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Journal of Food Engineering

journal homepage: www.elsevier .com/ locate / j foodeng

The utilisation of barley middlings to add value and health benefits to white breads

Paul Sullivan a,b,⇑, John O’Flaherty a,b, Nigel Brunton a, Elke Arendt b, Eimear Gallagher a

a Ashtown Food Research Centre, Teagasc, Ashtown, Dublin 15, Irelandb University College Cork, Cork, Ireland

a r t i c l e i n f o a b s t r a c t

Article history:Received 5 September 2010Received in revised form 23 January 2011Accepted 11 March 2011Available online 16 March 2011

Keywords:b-GlucanFibreMiddlingsBarleyMillingBreadDough rheology

0260-8774/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.jfoodeng.2011.03.011

⇑ Corresponding author at: Ashtown Food ResearcDublin 15, Ireland.

E-mail address: paulie.sullivan@gmail.com (P. Sull

The beneficial health effects of b-glucan, a major non-starch polysaccharide in barley, have become thefocus of much attention in recent years, with the incorporation of barley fractions into baked productsbeing a growing area in the development of healthier food products. In this study, flour formulations,doughs and breads were produced using the ‘‘middling’’ fraction (M) of wholegrain (WM) and pearled(PM) barley in different ratios (15%, 30%, 45% and 60% middlings with wheat flour). A 100% wheat formu-lation was used as a control. The protein content differed significantly (P < 0.01) between formulations(i.e. the amount of barley middlings substituted for flour) but did not differ significantly between WMand PM formulations of the same inclusion level. Starch pasting properties were significantly affectedby the increased inclusion of barley middlings (BM) into the formulation. Fundamental dough rheologyof the samples also showed significant differences between doughs made from different BM levels, withdoughs containing BM having increased firmness, decreased resistance to extension and decreased elas-ticity. Bread quality was not significantly affected by the addition of up to 30% BM, the loaf volume andtextural properties in particular of breads up to 30% BM inclusion were of a suitable standard when com-pared to the control. Both fibre and b-glucan content of the breads was increased significantly with theinclusion of BM; inclusion of BM at a 30% level increased the fibre and b-glucan contents, respectively.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

In recent years, the awareness of the consumer towards thebenefits of high fibre diets has increased. As a result, researchand manufacturing has shifted towards the production of fibre en-riched products such as high fibre breads (Newman et al., 1998).

Dietary fibre has been defined by AACC International (2001) as‘‘the edible parts of plants or analogous carbohydrates that areresistant to digestion and absorption in the human small intestinewith complete or partial fermentation in the large intestine’’ andcan be either a soluble or insoluble.

Barley is a good source of dietary fibre. However, traditionallybarley has not been used in the production of baked goods dueto its lack of gluten proteins, which lead to products with poor bak-ing and sensory attributes (Bhatty, 1999). At present, approxi-mately 2% of all harvested barley is used as human food, withthe rest being used in animal feed and the brewing industry (Baikand Ullrich, 2008). However, in recent times many studies haveshown barley consumption to be associated with lower serum cho-lesterol levels (Bourdon et al., 1999), as well as leading to moderate

ll rights reserved.

h Centre, Teagasc, Ashtown,

ivan).

postprandial insulin responses and blood glucose levels (Behallet al., 2004; Cavallero et al., 2002).

These health benefits are attributed in part to the soluble fibre(1 ? 3)(1 ? 4)-b-D-glucan (hereafter referred to as b-glucan). b-Glucan is abundant in both oats and barley and is a major compo-nent of the cell walls of barley endosperm.

The present study focuses on barley middlings, produced frommilled wholegrain barley and pearled barley. The work presentedassessed the chemical characteristics of middlings from milledwholegrain barley (WM) and milled pearled barley (PM) as wellas the physical aspects of the flours and doughs produced fromthem. The suitability of barley middlings (BM) for bread making(when used as composites with wheat flour) was also analysed.

The ‘‘middlings’’ fraction produced from the milling of barley ismade up of particles that are too big to pass through sieves de-signed to allow flour through, but small enough to pass throughsieves designed to separate out bran. As a result the middlings frac-tion is composed of a number of different particle types, includinggerm, large endosperm particles and smaller particles of the peri-carp, aleurone and subaleurone. The middlings fraction is of inter-est in the production of barley-containing breads as a previousstudy by Sullivan et al. (2010a) found the barley middlings fractionto have a high fibre content and in particular, a high b-glucancontent.

494 P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502

Currently, barley middlings are not widely used in the produc-tion of foods for human consumption and are a waste product inthe production of barley flour. Middlings are therefore more com-monly used in the production of animal feeds and so their benefitsare perhaps somewhat undervalued. Therefore if barley middlingscan be incorporated into a bread product without having a detri-mental effect on the quality of the product, this may have bothhealth benefits to the consumer and economic benefits to the foodindustry.

2. Materials and methods

2.1. Wheat flour

A standard commercial wheat flour suitable for bread making(Odlum Group Ltd., Dublin, Ireland) was used in this study.

2.2. Barley milling

Wholegrain barley grain (Sebastien, Spring 2007) was shippedto the Ashtown Food Research Centre in 3 � 100 kg batches. Thegrain was cleaned using a sample cleaner (SLN3, A/s Rationel Korn-service, Denmark) to remove any impurities and conditioned to14% moisture content prior to milling. Milling of the wholegrainbarley was carried out in a roller mill (Bühler AG, Switzerland) atAshtown Food Research Centre, Dublin, and was milled to a millingdegree of 70% following the AACC Bühler method (AACC, 1988).The milling produced two fractions of flour (break flour and reduc-tion flour) a bran fraction and a middlings fraction. The middlingsfraction was bagged and stored in a cool, dry room until use.

2.3. Peeled and pearled barley

Peeling and pearling of the barley was carried out by Bühler inSwitzerland (Bühler AG, Switzerland). Peeling involved the re-moval of the outer layers of the barley grain (6.2% w/w) and wasfollowed by pearling, where the peeled grain was polished, thusremoving further layers of the grain (4.1% w/w). The peeled andpearled grain was packed into 30 kg bags and sent to AshtownFood Research Centre for milling as previously described.

Both wholegrain and pearled barley have been chosen for thestudy to assess whether there is any differences in quality betweenthe breads produced from the two types of grain.

2.4. Flour combinations and bread formulations

After a number of preliminary baking tests using a wide rangeof barley middlings levels, four combinations of each middlingstype with a wheat control were selected for further analysis (seeTable 1).

The baking recipe was: flour, 2 g salt 100 g�1 flour, 3 g shorten-ing 100 g�1 flour, and 2.5 g fresh yeast 100 g�1 flour as well aswater (as guided by the preliminary baking tests and the resultsof farinograph measurements).

Table 1Flour combinations for wholegrain and pearled barley middlings baking trials.

Combination code Wholegrain middlings (WM) Pearled middlings (PM)

A 100% wheat flour 100% wheat flourB 85% wheat flour, 15% WM 85% wheat flour, 15% PMC 70% wheat flour, 30% WM 70% wheat flour, 30% PMD 55% wheat flour, 45% WM 55% wheat flour, 45% PME 40% wheat flour, 60% WM 40% wheat flour, 60% PM

2.5. Flour analysis

2.5.1. Protein2.5.1.1. Protein content. The wheat flour and barley middlings com-binations were analysed for protein content using a Leco proteinanalyser (Leco FP-428, Nitrogen Analyzer, Leco Corporation, St.Joseph, MI, USA). Each analysis was performed in triplicate.

2.5.2. Starch pasting propertiesThe pasting properties of the flours were determined with a Ra-

pid ViscoAnalyser (RVA-4D, Newport Scientific, Sydney, NSW, Aus-tralia). The 13 min test profile has a starting temperature of 50 �C,which is held for 1 min, raised to 95 �C in 3.7 min, held for 2.5 min,cooled to 50 �C in 3.8 min, and held for 2 min. Stirring speed is960 rpm for 10 s (to ensure dispersion of the grist) and 160 rpmfor the remainder of the test period. Results obtained from the testwere as follows: peak viscosity (highest viscosity during heating);time to reach peak viscosity; trough (lowest viscosity after cool-ing); breakdown (peak viscosity minus trough); final viscosity(maximum viscosity after the temperature had returned to50 �C); and setback (final viscosity minus trough) (Zhou andMendham, 2005; Zhou et al., 1998). All RVA analyses wereperformed in triplicate.

2.6. Dough evaluation

2.6.1. Uniaxial extensionUniaxial extension (on the Kieffer dough and gluten extensibil-

ity rig (Stable Micro Systems, Surrey, UK) was carried out on allthe samples (A–E)) using a similar method to that described byDunnewind et al. (2004). A texture analyser (TA-XT2i, Stable MicroSystems, Surrey, UK) fitted with the Kieffer extensibility rig andequipped with a 5 kg load cell was used.

During the test, the maximum force in tension and the displace-ment of dough samples were recorded. Three dough samples wereused for each formulation and the results were averaged.

2.6.2. Fundamental rheologyRheological measurements were performed on a controlled

stress rheometer (Anton Paar GmbH, Graz, Austria) fitted with par-allel plates consisting of a 25 mm serrated probe and 25 mm ser-rated base plate. Dough samples (based on 300 g of flour) wereprepared as previously described but without yeast. The sampleswere placed onto the base plate, and the upper plate was broughtto a gap of 1.025 mm where excess was carefully trimmed. Theplate was then lowered to a test gap of 1 mm and testing began.The whole system was covered using a peltier hood, with a tem-perature setting of 30 �C. The dough was allowed to rest for5 min to allow relaxation of residual stresses.

A frequency sweep from 0.1 to 10 Hz was performed with a tar-get strain of 10�3 (0.1%). Preliminary tests (amplitude sweeps)indicated that the strain was within the linear visco-elastic region.Silicon oil was used to ensure the sample did not dry out duringtesting. Ten measuring points were recorded. The temperaturewas kept constant at 30 �C using a peltier hood. Each result is theaverage of four measurements.

2.7. Bread evaluation

2.7.1. Baking trialsLoaves (300 g dough pieces in a 454 g tin) were prepared using

the formulations described following a straight dough baking pro-cedure. The doughs were moulded by hand and placed in the tins.The tins were transferred to a proover (Koma SDCC 1P/W, KomaKoeltechnische Industrie B.V., The Netherlands) at 35 �C and 80%

Table 2Protein content of barley middlings (BM) and wheat flour combinations.

Formulationcode

Flour/flourcombination

Protein (%)*

WMProtein (%)PM

A 100% wheat flour 11.73a 11.74a

B 85% wheat flour, 15%BM

11.37a,b 11.23a,b

C 70% wheat flour, 30%BM

10.92b 10.69b

D 55% wheat flour, 45%BM

10.52b,c 10.35b,c

E 40% wheat flour, 60%BM

10.12c 9.98c

– 100% BM 9.17** 9.05**

Values with different superscripts in the same column are statistically significant(P < 0.05).

* N � 5.7 for wheat flour and 6.25 for barley containing formulations.** Data taken from Sullivan et al. (2010a,b).

P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502 495

relative humidity for 65 min. The loaves were baked at 220 �C for22 min in a deck oven (Tom Chandley Ltd., Manchester, UK).

Six loaves were produced per batch. The loaves were allowed tocool for 2 h and their loaf volume was tested using a volume mea-surer (BVML370, TexVol Instruments, Sweden). The loaves werethen stored in polyethylene bags (two loaves per bag) at roomtemperature.

After 24 h, the first bag was opened and the two loaves weretested for crumb structure was assessed using image analysis withthe C-Cell Bread Imaging System (Calibre Control InternationalLtd., UK), and crumb texture was measured using a Texture ProfileAnalysis (TPA) programme using a texture analyser (TA-XT2i, Sta-ble Micro Systems, Surrey, UK) on two loaves. Two slices per loaf(four slices in total) were used for image analysis and for crumbTPA and the results were averaged. The loaf volume results werethe average of six loaves per replicate; for the image analysis,TPA, and colour measurements the results were the average of fourmeasurements per replicate (two slices from each loaf). This pro-cess was then repeated on the second bag after 72 h and the thirdbag after 120 h.

2.7.2. FibreFibre analysis was carried out according to AOAC Method

991.43, adapted for use with Foss Fibertec Equipment. Duplicatesamples (pre-dried, de-sugared and defatted as required) wereenzymatically digested to remove protein and starch. After precip-itation of soluble dietary fibre with alcohol, the total residue wasdried and weighed. One duplicate was analysed for protein andthe other for ash. Total dietary fibre was calculated as the weightof residue minus the weight of protein plus ash in the sample.

2.7.3. b-GlucanQuantification of b-glucan was performed with an enzymatic

method (Approved Method 32-23, AACC 2000) using a Megazymekit BBG (Megazyme, Bray Business Park, Bray, Co., Wicklow, Ire-land). The quantification was performed in triplicate from breadslice extracts of each formulation.

2.7.4. Taste panelSensory analysis was conducted on the five bread samples at

24 h post baking by 20 tasters, as per the method used by Sullivanet al. (2010b). Panellists were asked to assess the breads for accept-ability, and to mark a 6 cm line (0 = unacceptable, 6 = very accept-able) in accordance with their opinion. Results were analysed(ANOVA) as 5 samples � 20 trained tasters.

2.8. Statistical analysis

ANOVA one way statistical analysis was carried out using Mini-tab (Minitab version 15.1.1.0, Minitab Ltd., UK) to determine signif-icant differences measured in the properties of the flours, doughsand breads. Pearson’s correlation analysis between the variousparameters was also carried out using Minitab (Minitab version15.1.1.0., Minitab Ltd., UK).

3. Results and discussion

3.1. Flour analysis

3.1.1. ProteinA prior study by Sullivan et al. (2010a) found whole barley mid-

dlings (WM) and pearled barley middlings (PM) to have proteincontents of 9.17% and 9.05%, respectively, which are significantlylower protein contents than that measured in the wheat flour sam-ple (�11.74%). A lower protein content generally points to a lower

baking quality, so this would suggest that barley middlings maysignificantly affect the quality of BM-containing breads.

There were no significant differences between WM and PM for-mulations at the same inclusion levels (Table 2). There were, how-ever, significant differences (P 6 0.01) between formulations atdifferent inclusion levels. Increasing the BM concentration lead toa significant decrease in the protein content of the combinations(P 6 0.01). Protein plays an important role in dough structuraldevelopment, so a decrease in the protein content would suggestthat increased BM inclusion levels in the formulations may pro-duce doughs and breads of a lower quality than those with lowerBM inclusion levels.

3.2. Starch pasting properties

Tables 3 and 4 show the pasting properties of starch pastes fromWM and wheat composites and PM and wheat composites, respec-tively. Rapid-visco analysis measures a number of attributes offlour formulations that can give an insight into the quality of aflour formulation for use in bread making.

The substitution of BM for wheat flour significantly affected thepasting properties of the pastes (P < 0.01), however the level ofaddition did not significantly affect the pasting properties.

When comparing the pasting attributes of the wheat flour to theformulations containing barley middlings, it is apparent that peakviscosity, breakdown, final viscosity and setback were increasedfollowing the addition of barley. Bhatty and Rossnagel (1998)found that an increased level of b-glucan in starch pastes leadto an increased peak viscosity and setback. A previous study bySullivan et al. (2010a) found both WM and PM to contain signifi-cantly lower level of total starch than wheat flour, but to havesimilar amylose:amylopectin ratios. This may go someway toexplaining why there was no significant difference in the pastingproperties of the four composite flours (i.e. 15–60% BM addition).High amylose starches can require higher temperatures in thepresence of water to gelatinise fully due to the linearity of amyloseallowing the molecules to line up more readily and therefore forma more extensive network of hydrogen bonds (van Amelswoort andWestrate, 1992). The amylose contents of both BM fractions arecomparable to that of the wheat flour, and so their addition inincreasing amounts would therefore have little effect on the past-ing properties.

The difference between the control and the composite floursmay be explained by the presence of b-glucan in the BM fractions.b-Glucan has a high affinity for water (Brennan and Cleary, 2007),and therefore during heating when the starch grain is taking on

Table 3Rapid-visco analysis of wholegrain middlings (WM) and wheat combinations.

Formulation code Combination Peak viscosity (cp) Breakdown (cp) Final viscosity (cp) Setback (cp) Peak time (min)

A 100% wheat 1796a 893a 1929a 1026a 5.78a

B 85% wheat, 15% WM 2153b 1074b 2187b 1108b 5.80a

C 70% wheat, 30% WM 2109b 1052b 2192b 1135b 5.73a

D 55% wheat, 45% WM 2031b 1034b 2097a,b 1100a,b 5.87a

E 40% wheat, 60% WM 2098b 1053b 2159b 1114b 5.80a

Columns with different superscripts are statistically significant (P 6 0.05).

Table 4Rapid-visco analysis of pearled middlings (PM) and wheat combinations.

Formulation code Formulation Peak viscosity (cp) Breakdown (cp) Final viscosity (cp) Setback (cp) Peak time (min)

A 100% wheat 1796a 893a 1929a 1026a 5.78a

B 85% wheat, 15% PM 2063b 1031b 2175b 1143b 5.87a

C 70% wheat, 30% PM 2074b 1025b 2165b 1116b 5.80a

D 55% wheat, 45% PM 2059b 1025b 2182b 1148b 5.73a

E 40% wheat, 60% PM 2065b 1027b 2174b 1136b 5.80a

Columns with different superscripts are statistically significant (P 6 0.05).

496 P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502

water, the presence of b-glucan may mean that there is less wateravailable to the starch grain during this period. Another possibleexplanation may be differing starch granule sizes between wheatflour and barley middlings. If the middlings fractions were to con-tain starch granules of different sizes to the wheat flour, this maylead to a physical difference in the pastes during gelation (vanAmelswoort and Westrate, 1992), meaning that the granules inthe pastes are more closely packed and will therefore allow forthe amylose molecules in the granules to bond more readily, andtherefore more energy would be required to gelatinise the starch.This would suggest that breads containing BM will not gelatiniseas readily as the control bread and will therefore retrograde morerapidly than the wheat control.

3.3. Dough analysis

3.3.1. Dough rheology3.3.1.1. Fundamental rheology. Dough rheology plays an importantrole in the quality of baking products (Bloksma, 1990). There area number of parameters which can be measured as part of thedough rheology evaluation, which have been shown to give insightinto the behaviour of the dough (Metzger, 2006). Storage modulusrefers to the deformation energy stored in the material after oscil-lation is removed, and gives an indication of the material’s elastic-ity. The higher this value is, the more elastic the material will be.The loss modulus refers to the energy lost from the sample duringoscillation. If energy is lost, the sample cannot go back to its origi-nal shape, giving a measurement of the material’s viscousbehaviour.

In the present study, all doughs had a higher storage modulus(G0) than loss modulus (G00), indicating that the doughs had a solid,elastic-like behaviour (Table 5). Significant differences were ob-served in the rheological properties of the doughs as the levels ofBM increased. The control (100% wheat) had the lowest values ofloss and storage modulus, with the increased addition of BM lead-ing to significant increases in both the storage and loss moduli ofthe doughs. A study by Izydorczyk et al. (2001) also found thatthe addition of b-glucans and non-starch polysaccharides to awheat flour dough increased the elastic modulus of the dough.The authors suggested that the increase in both the (G0) and (G00)of the doughs were likely due to b-glucans binding water at a fasterrate, but to a lesser extent than gluten, and so a portion of thewater, although bound to the b-glucan, remained in the liquidphase.

Skendi et al. (2008) studied the rheology of doughs from differ-ent wheat cultivars and the effect of the addition of b-glucan to thedoughs. The authors found that the inclusion of b-glucan increasedthe G0 values of flours with good bread making quality flourdoughs, whereas decreased the G0 of poor quality wheat cultivars.These results would agree with the present study, where goodquality wheat flour was used. The authors suggested that thechanges in the dough rheology may be due to b-glucans havingthe highest affinity for water uptake in the dough followed by glu-ten and starch. Consequently, the distribution of water in thedough structure would be altered by the presence of b-glucans.

The complex moduli of the WM and PM dough formulations areshown in Table 5. It is apparent from the results that the complexmoduli differ significantly between formulations (P < 0.05). Thecontrol dough (100% wheat flour) had a lower complex modulusthan those containing BM, with a higher BM content in the doughsleading to a significantly higher complex modulus value. This indi-cates that the addition of BM to the doughs increases resistance todeformation, producing a more firm dough. This increased firm-ness may be due to the BM causing a change in the gluten matrixof the dough. When the BM level is increased, as a consequence,the amount of gluten available in the dough will decrease and soa weaker gluten matrix may be formed. As well as a decrease inthe gluten concentration of the dough, the addition of BM will in-crease the level of b-glucan in the dough. b-Glucan has a high affin-ity for water (Brennan and Cleary, 2007) and so may furthercompromise the ability of the dough to form a gluten network.With a weaker gluten network, less aeration of the dough will oc-cur during mixing and this may have a knock on effect to make thedough firmer. Barley middlings contain a high level of insoluble fi-bres compared to soluble fibres (Sullivan et al., 2010a). Theincreasing moduli values in the barley containing doughs maytherefore be attributed to the reduction of lubrication by waterdue to the increased competition for water absorption betweengluten and the insoluble fibres (Izydorczyk et al., 2001; Wanget al., 2003). Another possible reason for the increased visco-elasticmoduli readings may be due to the insoluble fibres acting as fillerin the viscoelastic matrix (Uthayakumaran et al., 2002).

3.3.1.2. Uniaxial extension. An increase in barley concentration inthe doughs significantly decreased the length the dough could beextended before rupture, while increasing the barley middlingsconcentration in the composite flours decreased the force requiredto bring about their rupture (Figs. 1 and 2). This would suggest that

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1.99�

106

(±6.

43�

104)

8.58�

105

(±3.

02�

104)

1.46�

106

(±6.

06�

104)

2.11�

106

(±5.

99�

104)

E8.

79�

105

(±2.

57�

104)

1.53�

106

(±7.

64�

104)

2.15�

106

(±1.

00�

105)

9.13�

105

(±2.

22�

104)

1.60�

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02�

104)

2.21�

106

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54�

104)

P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502 497

the elasticity of the dough was decreased by the addition of thebarley middlings.

Significant differences (P < 0.01) were observed between WMand PM doughs, with WM doughs resisting a greater force beforerupturing than the PM doughs. This would suggest that the struc-tural differences between WM and PM, as a result of the removal oflayers from the kernel during peeling, may have an effect on thebread making ability of the breads produced from the two differentBM types.

Brennan and Cleary (2007) produced doughs containing b-glucan (in the form of Glucagel�) from a barley source and foundthat increasing the amount of b-glucan in the dough lead to asignificant increase in the resistance of extension of doughs and alsoa significant decrease in the extensibility of the doughs, which is inagreement with the present study. Skendi et al. (2010) showed thatthe inclusion of b-glucan into a dough system weakened the glutennetwork of the dough by disrupting intermolecular associations ofgluten proteins. Therefore doughs containing higher levels of b-glucan will require less force to disrupt and will also be less elastic.

Angioloni and Collar (2009) studied the enrichment of wheatdoughs with fibres, finding that increasing the fibre levels in thedoughs had a significant effect on dough rheology, leading to a de-crease in extension and resistance to fracture. The authors sug-gested that these effects were due to the inclusion of fibresleading to gluten dilution and a disruption to the starch-glutenmatrix, which would agree with the results of the present study.Skendi et al. (2010) studied the effects of wheat doughs fortifiedwith barley b-glucan isolates and found that increasing the inclu-sion of barley b-glucan into the doughs decreased the extensibilityof the doughs and suggested that high addition levels could resultin a reduction of gas retention capacity in the doughs and a possi-ble deterioration in the gluten network structure during proofing.

3.4. Bread analysis

3.4.1. Loaf volumeIncreasing the BM concentration in the bread formulations de-

creased the final bread volume significantly (P 6 0.001) (Fig. 3).This is to be expected, as the protein/gluten concentration of theflour formulations was decreased with increasing levels of barleymiddlings in the breads. This gluten dilution, coupled with lessretention of CO2 gas, would lead to a decrease in baking quality(Sharma and Chauhan, 2000).

In the present study, it was found that inclusions of up to 30%WM and 15% PM, did not significantly affect loaf volumes. There-fore a wheat flour formulation containing barley does have the po-tential to produce a viable product.

3.4.2. Crumb structure (digital image analysis)Crumb structure is an important characteristic when evaluating

a flour for its bread making suitability. A good bread making flourshould produce a crumb that consists of a large number of smallsized, thin walled cells. Two slices, 1 cm thick from the centre ofeach loaf were scanned and the images analysed using the C-Cellsoftware (Calibre, UK).

Typical images of the loaves and slices from the bread formula-tions can be seen in Figs. 4 and 5, respectively. It can be seen fromthe figures that increasing the BM levels in the bread formulationsproduced loaves with a decreased height and volume.

3.4.2.1. Number of cells. The number of cells in a bread slice gives anindication of the amount of CO2 bubbles captured during proofing.For a bread slice to be considered to be of good quality, usually alarge number of small sized cells are desirable. It should be notedthat the C-Cell software has a resolution limit near 0.1 mm2, sosome smaller dough bubbles may not grow sufficiently to be

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70Displacement (mm)

Forc

e (N

)

A B C D E

A

B

C

E

D

Fig. 1. Uniaxial extension of doughs made from wheat flour and wholegrain barley middlings. (A) 100% wheat flour; (B) 85% wheat flour, 15% WM; (C) 70% wheat flour, 30%WM; (D) 55% wheat flour, 45% WM; and (E) 40% wheat flour, 60% WM.

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70Displacement (mm)

Forc

e (N

)

A B C D E

D

BC

A

E

Fig. 2. Uniaxial extension of doughs made from wheat flour and pearled barley middlings. (A) 100% wheat flour; (B) 85% wheat flour, 15% PM; (C) 70% wheat flour, 30% PM;(D) 55% wheat flour, 45% PM; and (E) 40% wheat flour, 60% PM.

498 P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502

counted by the system. The number of cells was significantly(P < 0.05) affected by the increased inclusion of BM, but was not af-fected by the type of middlings used (i.e. WM or PM).

In both WM and PM, the number of cells decreased when thelevel of BM inclusion was increased. The 40% wheat, 60% BM for-mulation, had an average of 2656 cells compared to 3023 in thecontrol. Up to a 15% BM inclusion, there was no significant differ-ence in the number of cells. This can be partly explained by thelower loaf volumes associated with barley containing breads, butit is also an indication that the inclusion of BM into the bread for-mulation leads to a more coarse structure. The decreased numberof cells could also be due to more CO2 escaping during proofing,and therefore a decreased number of CO2 bubbles being trappedin the dough structure. This would suggest a disrupted gluten ma-trix in the dough and would agree with other results recorded such

as the decreased loaf volume and slice area in BM containingbreads.

3.4.2.2. Area of cells. It is a common perception that the cell area ofbread crumb (or crumb fineness) has a significant effect on itsphysical texture (Pyler, 1988). The area of cells in a bread slicegives an indication of the size of the CO2 bubbles captured duringproofing. The area of cells was significantly (P < 0.01) affected bythe increased inclusion of BM.

In both WM and PM, the area of cells decreased when the levelof BM inclusion was increased, this was particularly significant at a60% BM inclusion level. The 40% wheat, 60% BM formulation, hadan average area of 51.12 compared to 52.96. Up to the 60% inclu-sion level the difference in cell area was not found to be significant.

0

100

200

300

400

500

600

700

800

A B C D E

Formulation

Volu

me

(cm

3 )

Whole Pearleda

a

a,b

b

c

a a

b

c

d

Fig. 3. Loaf volumes of the breads: (A) 100% wheat flour; (B) 85% wheat flour, 15% BM; (C) 70% wheat flour, 30% BM; (D) 55% wheat flour, 45% barley BM; and (E) 40% wheatflour, 60% BM. Columns with different superscripts are statistically significant (P 6 0.05).

Fig. 4. Baked loaves (L–R) (A) 100% wheat flour; (B) 85% wheat flour, 15% BM; (C) 70% wheat flour, 30% BM; (D) 55% wheat flour, 45% BM; and (E) 40% wheat flour, 60% BM.

Fig. 5. C-Cell images of loaf slices (L–R) (A) 100% wheat flour; (B) 85% wheat flour, 15% BM; (C) 70% wheat flour, 30% BM; (D) 55% wheat flour, 45% BM; and (E) 40% wheatflour, 60% BM.

P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502 499

The decreased area of the cells compared to the control wouldsuggest that the crumb structure of the BM containing breadswas more closed and therefore this could lead to a more ‘‘dense’’mouthfeel.

3.4.3. Texture profile analysisCrumb textural properties of the slices using TPA software on a

TA-XT2i texture analyser at 24, 72 and 120 h after baking. Two waystatistical analysis (ANOVA) revealed significant differences(P 6 0.001) among the formulations for hardness, resilience,chewiness, cohesiveness, springiness and adhesiveness. Of theproperties tested above, differences in the formulations are mostaccurately described when considering their hardness properties.

3.4.3.1. Hardness. Crumb hardness of bread slices containingwholegrain barley middlings (WM) and pearled barley middlings(PM) are shown in Figs. 6 and 7, respectively. It can be seen thatthe control (100% wheat) breads had the softest crumb, and

increasing the levels of barley in the formulations lead to a signif-icant increase (P 6 0.001) in the crumb hardness.

In both the WM and PM bread slices, hardness is particularly in-creased above the 30% level of inclusion. Therefore to produce asatisfactory bread product, this level of barley substitution shouldnot be exceeded.

The hardness associated with breads containing higher barleyinclusion levels may be related to the differing viscoelastic charac-teristics of the b-glucan present in these breads (Vaikousi et al.,2004) increasing the mechanical stress required to disrupt thebread’s structure.

Intrinsic hardness was calculated for each bread by relating thedensity of the bread to the hardness value measured by TPA. Cor-recting the crumb hardness for the density of the material showedthe same trend as had been found from the original TPA (data notshown), and indicated that the hardening effect exerted by theaddition of barley flour was not only due to higher density and in-creased porosity of the slices (Pareyt et al., 2008).

0

1000

2000

3000

4000

5000

6000

7000

A B C D E

Formulation

Har

dn

ess

(g)

Day 1 Day 3 Day 5

Fig. 6. Crumb hardness of breads containing wholegrain middlings (WM). (A) 100% wheat flour; (B) 85% wheat flour, 15% WM; (C) 70% wheat flour, 30% WM; (D) 55% wheatflour, 45% WM; and (E) 40% wheat flour, 60% WM. F-test: treatment (T) (P 6 0.001; sed 497.7), time (t) (P 6 0.001; sed 131.3), interaction (T � t) (P > 0.05; sed 552.4).

500 P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502

The hardness associated with breads containing higher barleyinclusion levels may be related to the differing viscoelastic charac-teristics of the b-glucan present in these breads (Vaikousi et al.,2004), suggesting that the increasing molar mass associated withthe b-glucans would increase the mechanical stress required todisrupt the bread’s structure.

Barley-containing formulations have also shown to be moresusceptible to starch retrogradation than the control, with theinclusion of barley being shown to produce a higher setback thanthe control in starch pastes (Sullivan et al., 2010b). This may ex-plain the increased hardness of barley-containing breads, particu-larly over a longer storage period, where the starch in the breadswill be more likely to retrograde. The increased barley content ofthe breads lead to an increased b-glucan content. Increasing b-glu-can will therefore reduce the availability of water, which wouldhave an effect of increasing the rate of staling in the breads.Stojceska and Ainsworth (2008) studied the effect of the additionof fibres, in the form of Brewer’s Spent Grain (BSG), to bread formu-lations and found fibre addition significantly increased crumbfirmness in samples containing high levels of BSG (20% and 30%),while no significant difference was found with a lower level(10%) addition. The authors suggested that the difference in firm-ness may be due to an increased presence of arabinoxylans inthe bread due to the addition of fibre.

0

1000

2000

3000

4000

5000

6000

7000

A B

Fo

Har

dn

ess

(g)

Day 1 Day 3 Day 5

Fig. 7. Crumb hardness of breads containing pearled barley middlings. (A) 100% wheat fl45% PM; and (E) 40% wheat flour, 60% PM. F-test: treatment (T) (P 6 0.001; sed 134.3),

3.4.4. Fibre analysis3.4.4.1. Total fibre. The fibre content of the breads increased signif-icantly (P < 0.001) with increasing levels of BM addition (Fig. 8). Aprevious study by the authors on the fibre content of barley mid-dlings found that barley middlings had a significantly higher fibrecontent than wheat (Sullivan et al., 2010a), and so this result is tobe expected.

When comparing the WM and the PM breads, it is apparent thatthe WM breads had a higher fibre content than the PM breads,although this difference is only significant (P < 0.05) at a 60% inclu-sion level. This difference may be due to small fibrous fragmentsfrom the outer layers of the barley being present in WM sampleswhich would otherwise be removed during peeling and pearling,and would therefore not be present in the PM fraction.

The FDA (2010) recommends a total dietary fibre intakes ofapproximately 25 g daily per day, of which �25% (�6 g) shouldbe soluble fibre. Therefore the increased fibre content of the BMcontaining breads (in which the inclusion of 30% BM more thandoubles the fibre content of the bread) would make this moreachievable to the consumer.

3.4.4.2. b-Glucan analysis. b-Glucan concentrations in the bakedloaves were significantly affected by the presence of barley mid-dlings (Fig. 8). There was no significant difference between the

C D E

rmulation

our; (B) 85% wheat flour, 15% PM; (C) 70% wheat flour, 30% PM; (D) 55% wheat flour,time (t) (P 6 0.001; sed 67.7), interaction (T � t) (P 6 0.001; sed 182.5).

0.00

1.00

2.00

3.00

4.00

5.00

6.00

A B C D E

Formulation

(%)

WM Fibre PM Fibre WM beta-glucan PM beta-glucan

a a

b b

c c

d

e

d

e

a a b b

c c d d

e e

Fig. 8. Total dietary fibre and b-glucan contents of breads containing differing BM levels. (A) 100% wheat flour; (B) 85% wheat flour, 15% BM; (C) 70% wheat flour, 30% BM; (D)55% wheat flour, 45% BM; and (E) 40% wheat flour, 60% BM. Columns with different superscripts are statistically significant (P < 0.05).

P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502 501

levels of b-glucan in WM breads and PM breads. Increasing theBM levels in the formulations lead to a significant increase in theb-glucan levels of the breads. Cavallero et al. (2002) and Dhingraand Jood (2001) also found that the substitution of barley into awheat flour formulation produced bread with a significantly higherb-glucan concentration than the wheat control.

According to the recommendation of the United States FDA(2005), food that contains barley must provide at least 0.75 g ofsoluble b-glucan per serving to qualify for the health claims statingthat the product reduces the risk of coronary heart disease. Giventhat the 30% BM breads contained approximately 1% b-glucan, itwas calculated that a serving size of 75 g would be required tomeet the claim. This equates to two slices of bread from a standard800 g loaf, which is a reasonable serving. This would suggest thatbreads containing 30% BM and above would be sufficient to qualifyfor this health claim.

3.4.5. Taste panelNo significant difference was found in the acceptability of WM

and PM breads (Fig. 9). Up to a BM inclusion level of 30%, there

0.00

1.00

2.00

3.00

4.00

5.00

6.00

A B

Com

Sco

re

Wholegrain Pearled

a a

a a

a

Fig. 9. Taste panel scores of breads containing differing levels of BM. (A) 100% wheat flo45% BM; and (E) 40% wheat flour, 60% BM. Columns with different superscripts are stat

were no significant differences in the acceptance of the breads,above 30% however the acceptability of the breads was shown todecrease significantly. Therefore it can be elucidated that a low le-vel BM inclusion level does not have an adverse effect on the con-sumer’s perception of the bread product, which would suggest,coupled with the b-glucan results, that a bread containing 30%BM has the potential to be commercialised.

3.5. Data correlation

There were strong correlations between various characteristicsmeasured in this study (Table 6). The phase angle of the compositeflours was found to correlate with a number of bread characteris-tics, in particular, the phase angle at 10 Hz was found to stronglycorrelate with specific volume (R2 = 0.986). There were also strongcorrelations between the phase angle of the composite flours and anumber of bread structural characteristics, in particular, the phaseangle at 10 Hz was found to strongly correlate with the number ofcells in the crumb (R2 = 0.908), identifying that a dough with anincreased phase angle was likely to yield a bread with a greater

C D E

bination

a

b b

c c

ur; (B) 85% wheat flour, 15% BM; (C) 70% wheat flour, 30% BM; (D) 55% wheat flour,istically significant (P < 0.05).

Table 6Correlations of BM containing flour, dough and bread characteristics.

Characteristic x Characteristic y R2 value

Phase angle Number of cells 0.908Phase angle Specific volume 0.986Peak viscosity Force of rupture (uniaxial) 0.979Breakdown Distance to rupture (uniaxial) 0.960Protein content Distance to rupture (uniaxial) 0.947Protein content Breakdown 0.913Protein content Specific volume 0.974Protein content Hardness 0.745Protein content Slice area 0.924Protein content Sensory scores 0.913b-Glucan content Setback 0.833b-Glucan content Final viscosity 0.895b-Glucan content Breakdown 0.994b-Glucan content Peak viscosity 0.937

502 P. Sullivan et al. / Journal of Food Engineering 105 (2011) 493–502

number of cells, and thus a more desirable final product. Thereforethere is potential for rheological tests to be used as a helpful pre-dictive tool in the development of quality bread products.

The b-glucan and protein contents of the flour formulationswere also found to correlate strongly with a number of doughand bread characteristics. Protein content and bread specific vol-ume of the resulting breads (R2 = 0.974), as was protein contentwith hardness (R2 = 0.745), slice area (R2 = 0.924) and with tastepanel results (R2 = 0.913).

4. Conclusions

The results of the study revealed that increasing the BM contentabove 30% lead to a significant decrease in the quality attributes ofthe resulting breads. However at a 30% inclusion level bread qual-ity was not significantly different than that of the wheat bread con-trol, yet the b-glucan and fibre contents of the breads weresignificantly improved. The breads at this level of inclusion wouldmeet the FDA recommendation of 0.75 g b-glucan per serving andso have the potential for commercialisation.

Acknowledgements

This project is funded by the Department of Agriculture, Fisher-ies and Food under the Food Institutional Research Measure.

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