Dough Conditioners in Wheat-Soy-Gluten Breads

The obiectives of this study were to develop soy flour­supplemented breads with satisfactory loaf characteristics and anexceJlent rating as a somce of dietary protein. Vital gluten anda variety of emulsifiers were used to compensate for thedeleterious effect of 10-25% soy f1our. Viscosity of the hot pasteflour slurries, mixograph curves of the dough, crumb and loafcharacteristics, and specífic volume were used as measures ofbread quality. In order to obtain a bread which contained at least13.5% protein, a wheat-soy-gluten blend in the ratio of 80:15:5was required. Sodium stearoyl-2 lactylate (SSL) (2.0g/100g)and l.Og SSL. + 0.5g Tween 6O/100g gave loaf characteristicsequivalent to or superior to the wheat f10ur control.

Materials and MethodsWheat flour and protein supplements

The wheat flour used in the present study was anuntreated baker's straight flour, commercially l11illedfrol11 hard red spring wheat. Proximate analyses bythe standard AACC (1968) methods demonstrated thatthe soy flour was higher than the wheat products inash and erude fiber (Table 1). While the protein con­tents of wheat flours are commonly estimated by the

51

S. E. Fleming and F. W. SosulskiDepartment of Crop Scíence

University of SaskatchewanSaskatoon, Sask.

protein content (45%, N X 5.7) and their ability toraise the PER for the wheat-soy flour blend to about2.0 (Campbell, 1960). In order to produce a bread witha protein rating over 40, a 13.5% protein blend whichcontained 80% wheat flour and 20% soy flour wouldbe required.

Defatted soy flours have been incorporated intobreads at the 5 - 7% levels with only moderatedeterioration in loaf characteristics (Ofelt et (1,7.,1954). Breads containing up to 11% soy flour(frequently formulated as 12g soy flour per 100g wheatflour) have been rendered acceptable by the incorpora­tion of natural and synthetic emulsifiers at lowconcentrations. Natural products such as lecithin 01'

plant gums may be used in foods, but most emulsifiersare synthetic esters of polyalcohols with fatty acids 01'

fats (Nash and Brinkman, 1972). Sorne functionprimarily as bread softeners and antistaling agentswhile others act predominantly as strong dough con­ditioners which permit greater tolerance in doughformulation and handling. Emulsifiers which havebeen effective as dough conditioners inelude theglycerol esters of mono- and diglycerides (Jongh, 1961 ;Jongh et al., 1968), sucroglyceride esters (Pomeranzet al., 1969, a, b) polyoxyethylene sorbitan esters(Langhans and Thalheimer, 1971) and lactylate esters(Tenney et al., 1968; Tsen et al., 1971), as well asmodified plant gums (Glicksman, 1969). When soyflour supplementaüon exceeded 11% (100:12:0), thephysical characteristics of the bread were too pOOl' foruseful improvement with dough conditioners (Tsen etal, 1971).

The objectives of the present investigation were todevelop soy flour-supplemented breads with satisfac­tor.y loaf characteristics and an excellent rating fürprotein quality. Gluten was added to the wheat-soyflour blends to partially compensate for the adverseeffects of the soy flours. In addition, several doughconditioners were utilized to improve the dough andloaf characteristics of the high protein breads.Viscosity of the flour slurries, mixograph curves of thedough, loaf volume, crumb characteristics and specificvolume were used as criteria of bread quality. Thenutritional evaluation of these wheat-soy-gluten breadswill be reportea in a separate papel'.

Résumé

Abstract

Introduction

. C~tte étu~e avait pour obj~ctifs de mettre ~u point des painsennchIs de farme de soya, possedant des caracteristiques de michsatiisfaisantes et une excellente cote comme source de protéinealimentaire. Du gluten "Vital" et une variété d'émulsifiants furentemployés pour corriger I'effet défavorable de la présence de1O-25~ .d<: farine, le~ courbes "mixographiques" de la pate, lescaractensbques de mlettes et de miche et les volumes spécifiquessont les parametres utilisés pour évaluer la qualité du pain. Ona di! employer un mélange blé-soya-gluten en rapport 80:15:5,pour obtenir un pain contenant au moins 13.5% de protéine. Lestearoyl-2 lactylate (SSL) (2.0g/100g) et le mélange 1.0g SSLavec 0.5g Tween 60/100g ont donné des caractéristiques demiche équivalentes ou supérieures a celles du témoin prépar- ala farine de blé.

Can. Inst. Food Sel. Technol. J. Vol. 7. No. 1. 1974

To satisfy the dietary protein requirements of anexpan~ing.",orld population, the protein quality andquantJty 111 cereal-based foods must be improved.Breads and other products made from wheat doughsare consumed widely in protein deficient areas andfortification with lysine-rich proteins from plant anda.nin~aI sources has been advocated by many nutri­tlOlllStS. Soybean proteins have an excellent distribu­tion of e~sential amino acids for correctinO' theimbalances in wheat gluten (Woodhal11, 1969).Unfortnnately, there are few nutritional guidelineswhich estimate the optimul11 level of soy flour in breaddoughs.

For l' e g u 1a t o l' y purposes, Campbell (1960)proposed a protein rating for foods based on thequantity and quality of protein in a reasonable dailyintake of food. Using the protein efficiency ratio(PER) as the measure of biological value, the "proteinrating" of bread was defined as the product of thePER and the gral11s of protein in 150g (5 slices). Forexample a white bread with a protein content of 8.4%and a PER of 1.0 had a protein rating of 9.6, while agluten-supplel11ented bread (protein = 16.9%, PER =0.9) gave a rating of 23. On Campbell's scale, a proteinrating (jf at least 20 was designated as a good dietarysource of protein and ratings above 40 were termedexeellent dietary sources of protein.

Soy flours are a better supplement for bread thangluten because of their low cost, moderately high

Table 1. Proximate eomposition of the wheat and soy flours andthe vital gluten (dry basis).

Table 2. Effeets of soy f10ur and vital gluten supplementationson protein eontent and loaf eharaeteristics of bread.

% soy f10ur % vital gluten in blendin blend O 5 10 15 20 25

Protein eontent of the bread (N x 5.7)O 10.6 12.9 14.6 15.9 18.2 20.15 11.4 13.3 15.5 17.2 19.2 20.3

10 12.3 14.6 16.3 18.2 20.1 21.815 13.3 15.4 17.4 19.2 21.2 22.020 14.4 16.4 18.2 20.5 22.1 23.825 15.5 17.4 19.0 20.9 23.0 24.5

Loaf volume of the bread (ce)O 885 920 D80 1100 1120 11505 830 905 965 1030 1100 1005

10 740 780 880 940 970 92015 650 700 720 725 795 85020 600 645 690 730 800 81525 550 575 630 680 615 700

Crumb grain rating (0-5)O 5.0 2.5 2.0 1.5 1.0 0.55 4.0 3.5 2.5 2.0 1.0 0.5

10 3.5 3.5 3.0 3.0 2.5 1.515 2.0 2.5 2.5 2.5 2.0 1.520 2.0 2.0 2.5 2.0 1.5 1.525 1.0 1.0 1.5 1.0 1.0 1.0

Crumb cOll1pressibility was measured with aBloom gelometer using a 4mll1 plunger and four one­inch slices cut froll1 the crown section of each loaf.Viscosity tests

The viscosity of 14.1% flour-water slurries weredetermined in a Brabender viscoall1ylograph by heatingfrom 30°C to 97.5°C and holding the slurry at thattell1perature for 15 min (AACC, 1968).

The desired absorption for the mixograph test(AACC, 1968) was considered to be the same as thebaking absorption.

Results and DiscussionSoy and gluten supplementation

In the absence of supplementary gluten, the addi­tion of soy flour to the wheat flour caused proportionaldecreases in loaf volume and crumb grain (Table 2).Nearly 20% soy flour in the blend was necessary toraise the protein content of tbe bread aboye 13.5%.However, blends with more than 11% soy flour(100 :12:0) rendered the loaf size and crull1b structureunacceptable by North American standards of breadquality (Tsen et al., 1971).

J. Inst. Can. Sel. TechnoJ. Aliment. Vol. 7. No 1, 1974

Gluten provides the structural frall1ework wbichdetermines the volume characteristics of the loaf. Thisframework is weakened by dilution with soy flour asevidenced by loaf volull1e depression (Ofelt et al., 1954;Pomeranz et al., 1969, a, b). The addition of vitalwheat gluten to the wheat and wheat-soy blendsresulted in improved loaf volumes up to the maximull1level of 25% replacell1ent of wheat flour (Table 2).However, the vital gluten contributed a eoarse andporous texture to the erumb in proportion to thequantity ineorporated into the flour blend.

Beeause of its high protein eontent (Table 1), thevital gluten had a marked influenee on the proteineontent of the breads (Table 2). However, the vitalgluten was by far the most expensive and had thelowest protein quality of the three protein sourees.

1.41.82.1

0.32.70.6

Bread Crude protein Ash Crude fiber Crude fatIngredients (Nx5.7)% % % %

12.3 0.546.1 6.481.5 0.9

Wheat f10urSoy flourVital gluten

nitrogen to protein factor of 5.7, recent studies byTkachuk (1969) and Sosulski and Sarwar (1973) haveshown that the same factor shGuld also be applied tosoybean and most vegetable proteins. Utilizing thisconversion factor, the soy flou!' and vital gluten con­tained 46.1 and 81.5% protein, respectively. The floursand gluten were reground to pass through a 100 meshTyler screen before blending.

Dough conditionersThe maximum limits of emulsifiers used in bread

products are regulated by Federal statutes and theirusage is eommonly within the range of 0.25 and 0.50%of the flour weight (Nash and Brinkman, 1972). Inthe present study, each dough conditioner was addedat three 01' four levels over the range reported to beeffective for that emulsifier.

The dough conditioners obtained in the powderedform - sodium carboxymethyl ceIlulose (C M C),methylceIlulose (MC), glyceryl.monostearate (GMS),and sodium and calcium stearoyl-2 lactylate (SSL andCSL) - were combined with tbe wheat flour and vitalgluten prior to mixing. Those in liquid form - sucrosemonolaurate (SML), and polyoxyetbylene sorbitanmonostearate (Tween 60) and monolaurate (Tween20) - were diluted 1:5 (w/v) with distilled water andincorporated at the dough stage. Combinations of solidand liquid emulsifiers were added separately at thestages described above.Breadmaking

Tbe breadmaking formula included 100g flour(14% mb), 4g NFDM, 3g shortening, 3g yeast, 5gsucrose, 1.75g saIt, O.lg llmmoniull1 phosphate mono­basic, 20 ppm potassiull1 bromate, 0.3g malt syrup,and water as needed. Where supplementary proteinwas added to the formula, the wheat flour was replacedwitb soy flour, 01' witb soy flour and vital gluten sothat the total blend was 100g. The proportions of eachconstituent were desiv,nated in the foIlowing order ­wheat flour: soy flour: vital gluten.

The dough was mixeu for 2 min by the straight­dough procedure (AACC, 1968) using a 3 hr fermenta­tion at 30°C and 80% rh. Baking time was 25 min at220°C in an experimental rotary oven. Loaf volumes ofbaked breads were determined by rapeseed displace·mento Weights and volumes of loaves were determined1 hr after the bread was taken from the oven. Whencool, the loaves were cut and the crust and crumbcolor, texture, and loaf shape were estimated using anumerical rating of O to 5 (optimum = 5, very pOOl'= O). Specific volumes were determined frOll1 theweight and volume data. Baking tests were replicatedat least twice and the average results are reported inthe foIlowing tables.

52

Table 3. Influen~e of dough conditioners on loaf characteristics and flour viscosity.

Loaf volume, cc.Blend andconditioner

Loaf characteristics at optimal Viscoamylograph curve at theLevel of conditioner, g/100g flour level of conditioner (") optimallevel of conditioner (")

O 0.25 0.50 1.0 2.0 Loaf Crust Crumb Specific Gelometer Time Peak Viscosityshape color grain volume reading to peak viscosity after 12min0-5 0-5 0-5 cc/g g min BU BU

515

490395

575

570430

52

5147

84

110115

5.0 5.0 5.0 6.3 104 46 690 5552.0 2.5 2.5 4.7 170 44 365 250

645" 580 2.0 3.0 1.0 4.2 184 44 365 255750 760" 3.0 4.0 2.0 4.8 141 43 620 380

740 740 745" 740 2.5 2.5 2.5 4.9 113 44 345 255770 810 835" 840 4.0 3.0 3.5 5.7 90 43 485 280790 800" 785 3.5 3.5 3.0 5.3 130 45 425 300800 800" 830 3.0 3.5 3.0 5.5 128 45 440 315

750 790 850" 3.5 3.0 4.0 5.8765 815 900" 4.0 3.0 4.5 6.0

760 800 820" 800 4.0 3.5 3.0 5.5850 3.5 4.0 2.5 5.6

915 4.5 4.0 3.5 6.1945 4.5 3.5 4.5 6.3

855700

100:0:080:15:580:15:5 + CMC80:15:5 + MC

+GMS+SML+ Tween60+ Tween20+CSL+ SSL+ GMS + Tween 60a+ SSL + Tween 60b

+ SSL + Tween 60b

+ SSL + Tween (JOb

The incorporation of the glycolipids, GMS andSML, into the wheat-soy-gluten blends had a morepositive effect on baking characteristics than the plantgums (Table 3). In particular, the SML treatment atthe 1.0g/100g flour blend gave nearly normal loaf sizeand shape although the crumb grain was relativelycoarse (Fig. 1) when compared to the control(100 :0 :0). Although the specific volume was slightIyless than the control, the crumb was actually softer bythe gelometer measurement. The viscosity tests on theflours demonstrated that the starch granule swellingand water absorption characteristics of GMS-and SML­treated slurries were still inferior to normal wheatfIours. The gluten development curves for theseglycolipid-treated fIours were not as strong as theUl~treaterl blend but compared favourably with thecurve for the wheat fIour. The present results support

a Tween 60 addcd to the indicated level of GMS in a 3:2 ratio.b 0.5g Tween 60 added to indicated levels of SSL.

Since the minimum protein level of 13.5% wasexceeded with the 83 :10:3 blend, this combination wasselected as the lowest cost formula for achieving theexcellent protein rating on Campbell's (1960) scale.However, the ratio of soy protein to wheat protein wastoo low to achieve the required PER 'Üf 2.0 :md the nexthighest combination of SO :15:3 was selected forfurther study in the present investigation. In futureexperiments, the proportion of gluten was decreasedto minimize the cost of additives in the bread formulaand adjust the protein to about 14.0%. At 13.4%protein, the SO :15:5 blend was lS3cc lower inloaf volume than the unsupplemented wheat fIour, andthe crumb grain was rated as average, 2.5 (Table 3).Therefore, studies on the infIuence of dough improverson the flour slurry, dough and loaf characteristics ofthis wheat-soy-gluten blend were initiated.Dough conditioners

Additional measurements on the control (100:0 :0)and SO :13:5 blend showed that the supplementedbreads were inferior in loaf shape and color (Fig. 1),specific volume and crumb softness; and the flourslurries were low in hot paste viscosity (Table 3).However, the infIuence of the 5% gluten was evident inthe strong mixograph curve for the supplementeddough (Fig. 2).

CMC was combined with the 80 :15:5 blend at 1.0,2.0 and 3.0g/100g flour. Each increment caused aprogressive deterioration in baking characteristics(Table 3). At the 1.0g level, the loaf, slurry and mixo­graph data were similar to the untreated blend. Thebeneficial effects of CMC on gluten development andhot paste viscosity reported by Glicksman (1969) andKim and de Ruiter (1968) were not observed in thepresent study. However, the unmodified plant gum,~fC, improved the loaf volume, shape, crust colour,crumb compressibility and the viscoamylograph curve(Table 3) but crumb grain (Fig. 1) and specific volumewere still pOOl'. A specific volume of at least 6.00 cc/gis required for an acceptable, marketable bread (Tsenet al., 1971). Further studies on the utilization of IJVICas a dough conditioner are warranted.

Fig. 1. Influence of dough conditioners on loaf characteristicsof an 80: 15:5 wheat-soy-gluten blend. On the left side, thecontrol (100:0:0) is shown over the 80:15:5 loaf. Fromleft to right in groups of three are the SSL, SML, Tween60; Tween 20, GMS + Tween 60, GMS; SSL + Tween

60, CMC and MC treatments.

Can. Inst. Food SeL Teehnol. J. Vol. 7, No. 1, 197453

the reports by Pomeranz et al. (1969, a, b) and J onghet al. (1968) that loaf volumes and crumb softness ofsoy-supplemented wheat flour and gluten-free starchbreads were improved by glycolipidso However, thecrumb grain remained relatively open and coarse.

Conditioning the doughs with the polyoxyethylenesorbitan esters - Tween 60 and 20 - were similar toS:M:L in their favourable influence on bread andviscosity characteristics of the wheat-soy-gluten blend(Table 3). However, none of the parameters were fullyequal in quality to the unsupplemented flour,especially in the high gelometer and the low hot pasteviscosity readings. The loaf characteristics of Tween20 supplemented doughs were similar to those treatedwith Tween 60 but Tween 20 adversely affected loafshape (Table 3) and the mixograph curve (Fig. 2).

The lactylate esters - CSL and SSL - weremarkedly superior to the other dough conditioners asimprovers of the soy-supplemented breads (Table 3).The characteristics -of loaves treated with SSL weresuperior to those with CSL (Table 3). This supportsthe results of other workers (Finney and Shogren,1971; Tsen et alo) 1971) oAt the high level of 200gj100gflour, the SSL-treated loaves were significantlygreater in loaf volume than the control (100:0 :0) anddemonstrated a desirable loaf shape and crumb texture(Fig. 1). While the crust color was relatively light, thespecific volume and crumb sofhiess of the SSL-treateclwheat-soy-gluten breads were almost identical to theunsupplemented control. The characteristics of thedscoamylograph curve for the SSL-treated blend weregenerally better than the other conditioners but onlythe gel stability after 12 min approached the controlvalue of 555 BU. The SSL-treated blend showed verystrong gluten strength and stability in the mixographtest (Fig. 2).

Finney and Shogren (1971) and Tsen et al. (1971)have demonstrated that CSL and SSL are excellentdough conditioners for wheat-soy blends. Tsen et ctlo(1971) incorporated 0.5% SSL into 11% soy flour(100 :12 :0) and obtained breads with specific volumesof 600. Tenney and Schmidt (1968) found that levels of005 to 1.0% SSL were optimum for wheat-soy blends.Because of the higher level of soy supplementation,2.0% (200gj100g flour) SSL was found to be optimumin the present study.

The dough conditieners used in the present studyhad differential effects on the wheat-soy-gluten blends,therefore, better overall improvement in baking qualitycould be achieved by combining certain improvers. Forexample, Langhans and Thalheimer (1971) found thata 3:2 combination of G:M:S and Tween 60 (Polysorbate60) was effective in improving bread quality becauseG:M:S softened the crumb while Tween 60 improvedloaf volumeo The same effects were demonstrated inthe present study, with the G:M:S and Tween 60­supplementecl breads showing the good characteristicsof the separate treatments (Table 3).

Several vther combinations were investigated andthe acldition of 1.0g SSL and 0.5g Tween 60j100g ofwheat-soy-gluten blend appeared to give the best over-

54

Fig. 2 Mixograph curveso

an flour and bread characteristics ('l'able 3). Theblend supplemented with 200g SSL and Tween 60 wassuperior tú the lower levels of SSL in crumb grain butgave excessively high loaf volumeso The 1.0g SSL andTween 60 gave good agreement with the control involume and specific volume characteristics. The lowcrumb compressibility rating for the 200g SSL andTween 60j100g blend would be increased with lowerlevels of SSL and would approach that of the control.The loaf volume was markedly superior to the controlbread and some reduction in the gluten content of theblend should be possible. This would perhaps permit[i. lower level of SSL and Tween 60 to produce a breadequal to the control. The loaf shape and crumb grainwere given high ratings but these would also beimproved by including less gluten in the blend. Thehot paste viscosity of the slurry was inferior to theunsupplemented control flour but other studies haveshown that this deficiency was due to the high level ofsoy flour in the blend (Matthews et ctl., 1970). The1.0g SSL and Tween 60-supplemented doughs gave astrong mixograph curve with long stability (Fig. 2)which was better than the 2.0g SSL and Tween 60clough characteristics.

ConclusionsA wheat-soy-gluten blend in the ratio of 80 :15:5

producecl a bread containing 15.4% protein whichshould qualify as an excellent source of dietaryprotein. While most dough conditioners improved someof the flour slurry, dough and bread characteristics,SSL in the concentration of 200gj100g blend and thecombination of 100g SSL and 0.5g Tween 60 gave loaveswhich were equivalent to the unsupplemented control.A reduction in the proportion of gluten in the blendwould be advisable in order to allow a further decreasein the level of dough conditioners and lower the overallcost of the high protein producto

AcknowledgementThe research project was supported by grants

from the Hantelman Agricultural Research Fund andthe National Research Council of Canada. The authorsare indebted to Mrs. D. Knapp for technical assistancein conducting the investigation.

J. Inst. Can. Sel. TeehnoJ. Aliment. Vol. 7, No 1, 1974

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Received Feb. 1, 1973.

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