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Evaluation of wheat quality for the baking of Syrian-type two-layered flat breads
Journal of Cereal Science7 (1988) 195-207
Evaluation of Wheat Quality for the Baking of Syrian-type Two-layered Flat Breads P. C. WILLIAMS*, FOUAD JABY EL-HARAMEINt, and JIT P. SRIVASTAVAt
w. NELSONt
* Grain ResearchLaboratory, CanadianGrain Commission,1404-303Main Street, Winnipeg, Manitoba, Canada R3C 3GB and t ICARDA, P.O. Box 5466, Aleppo, Syria Received21 April 1987 A procedureis presentedfor the evaluationof wheatquality by the bakingof Syriantype, two-layeredflat breads.A detailedsystemof scoringthe breadsis discussed.T he scoring systemis basedon dough-handlingpropertiesat dividing and sheeting,the crumb colour and texture, the eatingtexture,flavour and aroma,and the regularity in appearanceof the final product. The resultsof replicatebaking of flours of weak, mediumand high strengthshowedthat the precisionof the test wassatisfactory.The procedurewas further illustratedby the baking of flours of severaladvancedlines of wheat,using a Syrian local commercialbaker'sflour as a control. The study verified that flours of medium strength tend to produce the best type of two-layeredflat breads.
Introduction During the past10 years,severaltypesof flat breadhavereceivedthe attentionof cereal scientists.The factors involved with baking Egyptian baladi breadl - 6 and Iranian and other Arabic type breads7 have beendiscussed. Arabic, two-layered,flat (2LF) breadsor 'khobz' differ from conventional raised breadsin their very characteristicshapeand texture,andfrom single-layeredbreads,of which many versionsexist. The procedurefrom mixing to baking is essentiallysimilar to that of raisedbreadsexceptfor the productionof the final flat dough piecesand the high oven temperatureat baking, which is in part responsiblefor the formation of the two layers. During primary fermentationthe dough fermentsand developsto give the familiar spongyappearance,texture and smell. The short relaxationperiod, or interproofbetweendividing and roundingandsheetingis importantsinceit hasa significant effect on the crumb texture of the final bread. When the dough enters the oven at 450 DC, the millions of minute gas bubblesthat have re-formedafter sheetingexpand very rapidly, causing the dough to inflate to a balloon-like appearance.W hen the 'balloon' burstsunderthe pressureof the expandinggasesinside,the top half collapses onto the bottom half to give the familiar two layers. In traditional Egyptian baladi Abbreviations used: 2LF = 2-layered flat (bread): ICARDA Researchin the Dry Areas. 0733-5210/88/020195 + 13 $03.00/0
= International Center for
Agricultural
© 1988 AcademicPressLimited
196
P. C. WILLIAMS ET AL.
bread, which is baked from high moisture (75-90% water absorption)doughs, the formation of steamalso contributesto the separationin the oven. Single-layeredflat breadsdiffer in several ways:they are bakedmainly from very high (up to 100 %) extraction flours, they are usually either fermentedby a sour-doughmethod or are essentiallyunfermented,a ndthe bakingtemperatureis significantly lower. As a resultof the combinationof all threefactors the gasbubble complexis not presentto the same extentin the doughs,and this, combinedwith the lower baking temperature,doesnot promotethe formation of the two-layeredstructure. The best types of 2LF breadshave a fine 'crumb' causedby the developmento f tb.e many small bubblesof carbondioxide during the final proof. The 'crumb' is the inner wall of eachlayer. The breaditself is densesincethe layers are essentiallysolid, but of a pleasant' al dente'type of biting texture.The correctcombinationof formulation and fermentationhasa critical influenceon the quality of the bread,andindividual bakeries differ widely in the quality and customeracceptabilityof their products. During 1980-1982a surveyof over fifty 2LF breadbakeriesin threecountries(Syria, Lebanon and Jordan) was carried out by the ICARDA (International Center for Agricultural Researchin the Dry Areas)cerealimprovementprogramme.A wide range in formulae and procedureswas encountered,and the resultsare summarizedin Table I. The mixers usedwere either of the wishbonetype (most widely used),swinging arm, or spiral mixers (usually in automaticbakeries).In only a few caseswere temperature
TABLE 1. Summaryof practicefor baking two-layeredflat breadsin Syria, Lebanonand Jordana Range High Ingredients(% of flour weight): Flour Water Yeast(dry) or: Yeast(compressed) Salt Sugar Procedure: Mixing time (min) Fermentationstandingtime (min) Divide: weight (g) Interprooftime (min) Sheetingthickness(mm) Final proof time (min? Baking time (min) Temperature(0C)
100 70 0·5 5
1·5 3
35 60 300
20 3 40
3 500
Low 100 40
0·15 1'5 0'3
o
8
10 195 5 1'5
o
0·5 300
• Figures are necessarilyapproximate,since most bakers measureingredients by volume in various receptacles,r ather than by weight. b Dough piecesare sheetedin two directionsbetweenintermediateand final proof.
WHEAT QUALITY FOR FLAT BREADS
197
and humidity controlledduring fermentationor proofing. Ovenswere usuallyoil-fired, but occasionallywood-fired, and temperaturecontrol was achievedby regulating the flow of oil, or by stoking (of wood burning ovens). Syria, Lebanonand Jordanare net importersof breadwheats,either as wheator as flour. In SyriaandJordan,flours milled from local breadanddurumwheatsareblended with imported('zero' flours), or with flours milled from importedwheat.Consequently, the bakersare faced with frequentchangesin the behaviourof the flours. In Lebanon, very little wheatis grown, andnearlyall flours aremilled from importedwheat(usually from Canadaor the U.S.A.). Importsby the 22 countriesof North Africa andWestAsia (including Afghanistanand Pakistan)haveincreasedby 190 % between1972-82, from 4·9 million to 14·2million tonnes,andareprojectedto reachwell over 100million tonnes by the end of the century.In view of thesefigures (basedon United Nations Food and Agriculture Organization(FAO) estimates),it is essentialt hat stringentefforts be made to increasethe productivity of cereals,andwheatin particular,throughoutthis region, which hasa rapidly growing populationof closeto 400 million. It is equally important thattheincreasein productivityof wheatis basedon varietiesthat areacceptableto both the processingindustry and the consumer,sinceif this is not so, the ensuingincreasein wastagewill tend to offset the increasesin productivity. ICARDA has establisheda laboratory in Aleppo, Syria for the evaluation of germplasmof the breadwheatand durum wheatbreedingprogrammes.B oth types of wheat are used for baking flat breads. This report describesthe experimental2LF breadbaking procedureand factors used in judging the dough strength and overall baking quality.
Experimental At ICARDA, all advancedlines of breadand durum wheatsand triticale aremilled into flour on a Buhler Model MLU 202 laboratorymill. Flour extractionis calculatedfrom the total of all six flour streamstogetherwith flour from the bran finisher, on the basis of the original tempered wheat. The flours are tested for water absorption and dough strength with a Brabender Farinographusing the 50 g bowl. Absorption is taken as the amount of water taken to give a doughwith a consistencyof 500 BU at peakdevelopmenttime, using 50 g of flour on a constant (14 %) moisturebasis. Baking quality is testedby baking commercial-typeSyrian 2LF breads ('khobz'). A small-scale,wishbonemixer (Fig. 1) was designedand madelocally by an engineeringfirm in Aleppo. The optimumcapacityis about600 g flour. The wishbone-typemixing armsrotateat an angleto the bowl, which turns freely on a spindle.The doughis forced againstthe wall of the bowl by the action of the mixing arms,causingthe bowl to rotate continuouslyduring mixing. Doughsaredivided by handandscaled.Thesheetingrolls weremadein Aleppo, andareidentical with the equipmentsuppliedto small bakeries.Doughsaresheetedin two dimensions.The dough balls arefirst rolled into a long flat oval doughpieceabout8 mm thick. Thesearepassedthrough the secondset of rolls and sheetedto round piecesof up to 2 mm thick and 28-30emdia. They emergeonto a canvasbelt, which canbe stoppedby slight pressureof the handto transferthe flat dough piecesonto a board for final proof. The ovenis a traditional type of bakeryovenor 'fourn' built at theTel HadyaResearchCentre, Aleppo, by a stonemason,whosespecialityis building bakeryovens.This enabledbakingquality • to be evaluatedby a procedureconforming closely to local and regional baking practice. A schematicdiagramof the oven,which is fired by a mazout(fuel oil) burner,is givenin Fig. 2 (full details of the constructionof the 'fourn' are availableby request).
198
P. C. WILLIAMS ET AL.
FIGURE 1. Action of 'wishbone'mixer.
TABLE II. ICARDA baking procedurefor two-layeredflat bread
Amount Ingredients Flour Yeast (compressed)" Salt Sugar Water (30°C) Procedure Mixing time Primary fermentationtime Divide Interproof time Sheetingthickness Final proof time Baking time Oven temperature
600 g
9g 6g 6g 330 ml"
% (flour weight basis) 100 1·5 1·0 1·0 55
10 min in 'wishbonemixer' 45 min 200 g 10 min "5-2 mme 25 min 35-50 s 450--470°C
• If dried yeast,3 g (0'5 %) is used. b Water addition varies accordingLo Farinographcharacteristics.Weak flours are baked at 50% water absorption.Wateris addedin incrementsof 2 % up to 60 %, which correspondsto about70 % Farinograph absorption. C Strongerdoughsare sheetedthinner.
WHEAT QUALITY FOR FLAT BREADS
[99
::.:.:::..•••••:::.:,'::. A :,,:.:.:::;;{.:,: :'::'.: I I
(0)
E
Q
( b)
FIGURE 2. Diagramsof baking oven (a) front and(b) overhead.A, absorbente arth base;B, brokenglassfilter layer; C salt insulation; D, concreteblock internal wall; E, concreteblock external wall; F, brick dome oven ceiling; G, cementlayer; H, accessdoor; J, burner; K, air space;L, basaltoven wall; M, basaltoven floor; N, flue; P, steel baffle plate; Q, limestoneslab doorway sill. The rCARDA baking test was basedon the observationsmadeduring the bakery survey. It representsa practicable'average'formula and procedure,a nd is summarizedin Table II. Baking absorptionis varied in incrementsof 2 %, accordingto Farinographabsorption.For optimum dough-handling,baking absorptionwas found to be 4-8 % lower than Farinographabsorption (50 g bowl). Flourswith Farinographabsorptionof 56-57% hadgooddough-handlingproperties at about52 % bakingabsorption,whereasa flour with 68-70% Farinographabsorptionhandled well at 60-62% baking absorption.
200
P. C. WILLIAMS ET AL.
The standardformula canbe changedto accommodatemoreor lessflour; otheringredientsare then recalcu.1atedon a percentagebasis.Doughsare mixed in the wishbonemixer using water at about30 °e, then coveredwith a cloth and a plasticcoverto maintainthe relative humidity, and kept at 25 ± 2 °e. Thesefermentationconditions simulate, but are superior to, those of most commercialbakeries,whereseasonalfluctuationsin the ambienttemperaturearecompensatedfor by adjusting the formula and fermentationconditions. Sugaris sometimesusedin commercial bakeriesto acceleratefermentation,and salt to retardit. At ICARDA, doughstrengthis judgedat the dividing andsheetingstages.The total weight of dough preparedallows for four, full-sized (200 g) dough pieces (loaves), with a small piece (130-150g) left over. This small piece is rounded and inter-proofed in the normal way, and usedto test the sheetingconditions.The rolls are set accordingto the behaviourof this dough piece.If the small or 'pilot' doughis very strong,the rolls areadjustedto give a thinnerfinal dough piece, or a slightly thicker one if the dough appearstoo weak; this is the systempractisedin commercialbaking. After sheeting,the flat doughsare placed on boardsfor final proofing. Both intermediate and final proofing are carried out under the same temperatureand humidity conditionsas the primary fermentation.The doughsarebakedat about450 ± 10 °e. Baking time is 40-50 s. Thefinal2LF breadis cooledfor about10 min, temporarilystoredin plasticbags,and judgedthe sameday. Threeloavesarejudgedfrom eachbake.The fourth may be usedto judge keeping quality: it is placedin a plastic bag and left overnight at room temperature.I t is then folded tightly. The patternof crackingis a measureof keepingquality, and a further indication of strength.Baking at optimum water absorptionfor the flour is critical to the keepingquality test.
Judging and scoring Judgingis, by nature,subjective(exceptfor diametermeasurement),andjudging of threeor more loavesreducesthe risk of errorsin judgement.Doughsfor determinationof specificcharacteristics and genotypesintended for advancementto national programmesare preparedat least in duplicate,so that judgementsare basedon six or more loaves.The arbitrary numerical scores given for particularquality traits are given at the end of eachsection(scoresfor eachare 1-5). a and b. Dough handlingproperties. Thesepropertiesat dividing and sheetingare very important in 2LF bread baking, sinceif dough handling propertiesare poor the flour causesproblemsin bakeries.Most of the bakeriesin the Middle Eastcall for fairly extensivephysicalmanipulation of the thin, flat doughpiecesbetweenmixing and baking, particularly in automatedbakeries.If doughsare too weak, they becometoo thin at sheetingandholesdevelop.Very weakdoughsfall betweenthe fingers in manual bakeries,and causeseriousproblems in sheetingin automatic bakeries.On the otherhand,very strongdoughswith high elasticityshrink aftersheetingand give thick loaveswith poor textureand 'biteability'. Whenvery weak doughsaresheetedthinly, they becometough and 'chewy' in baking and less attractive to the consumer.Weak doughs also becomestale and hardenmore quickly than strong doughs.Dough-handlingat dividing gives a goodindicationof baking(water)absorption,andflours with very poor handlingat dividing may be re-bakedat different water absorption.
Scoring (a) Dough handling at dividing: 1W, Very weak, sticky and difficult to mould; or IS. Very stiff anddifficult to form a ball without cracking.2W, Weakand difficult to mould; or 2S stiff and difficult to mould. 3, Fair handling. 4, Good handling. 5, Very good, 'lively' feel. Scoring(b) Doughhandlingat sheeting:1W, Very weak and fragile, not possible to obtain good intact dough piecesevenafter resheetingat 2·0 mm. 2W, Weak and fragile, remouldingand resheetingnecessary.3W, Fair handling. 4, Good handling. 5, Very good handling properties.Alternative: 18, Excessivelystrong (i.e. excessive elasticity),doughpiecesshrink evenafter resheetingat 1·0 mm. 28, Very strong(too muchelasticity),doughpiecesneedresheetingat 1·0 mm. 38, Strongerthanoptimum but nO resheetingnecessary.
WHEAT QUALITY FOR FLAT BREADS
201
Differences between'fair' and 'good', 'good' and 'very good', etc., are subjective,and are evaluatedby comparisonwith flours of known, professionally-evaluated bakingperformance. c. Colour andappearance.Off-coloursand burnt patchesarevery noticeableon the surfaceof flat breads.Grey colour can be causedby foreign materialon the outsideof the grain beforemilling, by the milling operationitself, by small amountsof oil extrudedfrom the mixer, by fungal spores and by other agencies.Several commercial flour mills have been installed very recently, in Northern Syria, and they mill to 80 % extraction. In addition, bunt (Tilletia caries) is very prevalentin the regionS,so that grey is the off-colour mostfrequentlyencountered.Nevertheless, the doughstrength,diameterandcrumb textureenablean evaluationof the inherentstrengthof a flour. Burnt patchesusually indicate inadequatefermentation,over-fermentation,or high aamylaseactivity. Ideally 2LF breadshouldbe of an evencreamto pale brown colour, with no patches.2LF breadbakedfrom durum flours or flours with a high proportion of durumtend to be yellow. Scoring; 1, Grey, yellow or very burnt, or holes. 2, Lighter grey or yellow, less burningor holes.3, Paleto white, patchesapparent.4, White to paleyellow or pale yellow/brown. No burnt patches.5, Pale to light brown colour, even colour over whole loaf. d. Diameter. For a 200 g doughpiecethis shouldbe about28-30em. If doughis too strong, the diametercan be as little as 15-20em; if the dough is too weak, it can be 35-40em, with holes. Diameteris measuredin two dimensionsand the ratio of one diameterto the other calculated. Pointsare subtractedfrom the scoreif the loaf is not round. Regularityin the roundnessof 2LF breadloavesis alfectedby the efficiency of roundingthe doughpiecesat the dividing stage,but mainly by the two-dimensionalsheeting.Weak doughstend to stretchso much during the first sheetingthat they do not resumeroundnessat the secondsheeting.Very weak doughsmay have to be re-rounded,relaxedand re-sheetedbefore a bakeabledough piece can be achieved.This affects the crumb textureof the final bread.
Scoring; Diameter lW, Above 36 mm with holes 2W,34-36mm 3W,32-34mm 4W,3D-32mm 5,28-30mm 4S, 25-28mm 3S, 22-25mm 2S, 19-22mm IS, less than 19 mm
Ratio
Points subtractedfrom score
1; 1·05 1; 1·15 1: 1·25 1: 1·35 1; 1'45 1: 1'55
0·5 1·0 1'5 2·0 2'5 3'0
e. Crumb texture. Internal crumb should be rich in smail cens 1-2 mm in diameter, evenly distributed about both internal surfaces.Large-celledstructureis referredto as coarsetexture. Sometimesthe internal crumb is waxy, which meansthat there is no cell structure.Another characteristicis that layers may not part evenly. When this happens,somepartsof the internal surfacewill havegood cell structure,and other partswill have no cells, but will appearto have a 'waxy' surface.Texture is strongly affected by fermentation,and poor texture is usually an indicationof under-or over-fermentation(Fig. 3). It is alsoaffectedby the sheeting.If the dough pieceis too thick, the cells of the final loaf will be large,with thick cell walls. This is often the case if the doughsare too strong.They contractafter sheetingto give a thicker doughpieceandpoor, coarsetexture.
P. C. WILLIAMS ET At.
202
. ....
(a) " ~.'
FIGURE 3. Crumb texture of two-layeredflat bread Ckhobz'): (a) excellent; (b) coarse,open (poor); (c) very good; (d) waxy, indicatespoor fermentation.
WHEAT QUALITY FOR FLAT BREADS
203
Scoring: 1, Densewaxy texture, no visible cells. 2, Waxy texture, somecells. 3, Moist appearance,smaller cells. 4, Moist, large patchesof small uniform cells. 5, Moist, small, uniform cells, crumb even, with no patches.Alternative: IC, Very coarseopentexture,very largecells(usuallyassociatedwith loavesof smalldiameter). 2e, Coarseopen texture, large cells.
f Separation.Separationof the two layers should be even, and each layer should be about 1'5-2'2 mm thick. Frequentlyone layer will be thicker than the other. This candevelopduring proofing, dueto bubblesof gasforming closerto onesurfacethan the other. It canalso becaused by ovenconditions.If the ovenis too hot at the floor level, the bottomlayerwill be thin, and often burn. At the sametime, the other layer will be too thick and will have poor crumb texture and 'biteability'.
Scoring: I, No separation,o r only partial separation.2, Very unevenseparation, one layer less than I mm. One layer over 3 mm. 3, Uneven separation, 2 mm difference betweenlayer thickness.4, Even separationacrossmost of loaf. 5, Even separationin all areas. g. Smell.Smellsor odoursarecausedby small amountsof aromaticsubstancessuchas estersor ketones,or by burningand caramelizationof sugars.Moulds may also causeodours.Smell is an importantcomponentof taste,and should be judged separately. Scoring(smellsshould be identified if possible):I, Very strongsmell of 'burnt' or other taints. 2, Definite smell of 'burnt' or other taints. 3, Faint smell of 'burnt' or other taints. 4, Bland smell, no identifiable substances;5, Positive pleasantsmell of 'fresh bread'. h. 'Biteability'. This is testedby biting the bread.2LF breadmay be soft, chewyor sticky, tender
Cal dente'),toughandleathery,or hard.Theseconditionsreflectpropertiesof the flour, sincethey arecausedby a combinationof partial starchgelatinization,watercontentat baking, andprotein denaturationduring baking. If the protein contentof the flour is high andstarchdamageis low it is likely that the resultant bread will be tough or heavy to bite. On the other hand, highly damagedstarchabsorbsa lot of waterand leadsto a higherdegreeof starchgelatinization, giving a softercrumb. 2LF breadbakedfrom puredurum flours havea softer texturethan thosebaked from breadwheatflour, andin general,the softerthe wheat,the harderandmore'cardboard-like' are the bakedloaves. Scoring: 1. Very tough leatheryfeel; hard to chew. 2. Tough. 3. Very sticky when chewing. 4. Slightly sticky when chewing. 5. Pleasantand easy to chew, 'al-dente' type. 4S. Soft and less 'body'. 3S. Very soft. j. Taste. 2LF bread should tasteof the ingredientsafter they have undergonemodification by
fermentation,and the heat of the oven. Most flours give loaveswith acceptabletasteand smell. Off flavours can be causedby acid developmentduring fermentation,by moulds,too much yeast or salt, too much sugar(which will causecaramelizationand burning), and by burning itself. Mouldy, tainted or otherwisedamagedflours can also impart poor flavour and aroma. Scoring: I, Very poor taste due to off-flavours or burning, difficult to swallow, strong and unpleasantafter-taste.2, Poor taste due to off-flavours or burning. Unpleasantafter-taste.3, Fair taste. 4, Good taste. 5, Excellent taste, and after taste. k. Keepingquality. Flourswith poor strengthusually will retain the textureof the 2LF breadonly for a shortwhile after baking. If a loaf is folded tightly it will tear andmay breakup completely. Othersmay not crack at all, and theseare referred to as strong.
204
P. C. WILLIAMS ET AL.
Scoring: 1, Breadpiecesdisintegratecompletelyon folding. 2, Heavy tearingover all areas.3, Tearingat centreandadjacentto centre.4, Slight tearingnearcentreonly. 5, No cracking, khobz completelyresistantto tearing.
Overall score The overall total possiblescoreis 50, with the highest total scorebeing the best. This method enablesthe bakerto detectwhy individualflours vary. In anysetof flours tested,a particularflour may havea low overall scorebecauseof one bad characteristiceventhoughit is goodin others. This one badcharactercould causedifficulties in commercialbaking, and it would be important to identify sucha factor beforea variety becomeslicensed.The systemis also helpful to breeders, particularly when the progenyof wide crossesare being evaluated.
Results and Discussion
To determinethe reproducibility of the bakingprocedure,threedifferent Buhler-milled flours were used. Five replicateswere baked, and the fifteen doughsrandomizedfor bakingand also for judging. The resultsof baking thesethreeflours aresummarizedin TableIII. Theflours differedconsiderablyin strength.TheaverageFarinographstability of the weaker flour was 3·2 min, and the medium strength and stronger flours respectively6·3 and 12·7min. Extractionof the flours was respectively72, 76 and 75 %. Precisionfor scoring the nine characteristicswas good and the overall precisionof the bakingscorewas 0·97 pointsfor a coefficientof variability (CV) of 3·0. Leastsignificant difference betweenmeansfor baking scorewas 1·9 points (P = 0,05). The analysisof variancefor eachparameteris summarizedin Table IV. Most flours gave breadwith reasonableto very goodtasteandsmell. Theparametersfor which differencesweremost clear-cutwerethe doughstrengthat dividing and at sheeting,the biteability andcrumb texture,the colour andthe overall score.Differencesin doughstrengthat sheetingwere very noticeablebetweenthe three flours. This is a particularly critical factor in both manual and automatic 2LF breadbaking.The results also indicated that, for 2LF breadbaking,the medium-strengthflours were generallysuperiorto either strongeror weaker flours. Stronger flours were superior to weaker flours in dough-handling properties,but inferior in crumb and separationcharacteristicsand biting texture,due to the increasedthicknessof the final dough piece. Medium-strengthflours were wellbalancedin all parameters. TableV illustratesthe resultsof applyingthe abovebakingandscoringprocedureto five unknownwheatlines (2-6), with a commercial,80% extractionflour as a control. All the test flours were Buhler-milled from advancedbread wheat lines from the ICARDA cereal programme. Extraction rate varied from 72 to 76%. Clear-cut differenceswere apparentbetweenthe lines, with No.2 being the poorestin several categories.N umber6 was consistentlyscoredhighly, and was equalor superiorto the commercialbaker'sflour in all parameters.Differencesbetweenflours in flavour and aromawerestatisticallyinsignificant. The scoringof theseorganolepticparametershas little practical value unlessthe baking procedureis to be applied to a study involving changesin baking formula. such as salt or sugar content, or to tainted or otherwise damagedflours.
TABLE III. Quality evaluationscoresand reproducibility of bakingprocedurefor two-layeredflat breadfrom flours of different strengths"b Dough handling
Flour
Mean S.D.
Mean S.D.
Dividing a
Sheeting b
3·5 2·5W 3W 2·5W 3W
2·5W 2·5W 2W 2W 3W
2·9 0·4
2-4 0·4
4·5 4 4'5 4·5 4
4·5 4 4·5 4·5 4·5
4·3 0·27
4·4 0'22
Colour
c 4 4·5 4 4 4 4·1 0·2 4 4·5 4 4 3'5 4·0 0·35
Diameter Separation Crumb Aroma d e f g
4·5 3·5 3·5 4·5 5 4·2 0·7 4·5 5 3·5 3·5 3·8 4·1 0·67
A (weak) 2 2·5 2·5 3·5 3 2·7 0·6 B (medium) 4 4·5 3·5 3 3·5 3·7 0·57
3·5 4·5 4 3·5 3
3·5 3 3 4 3·5
Taste
i
3·7 0·6
3-6 0·7
3-4 0·4
4 4·5 4·5 3·5 3'5 4·0 0·5
3W 4'5 3·5 3·5 3W
4 4'5 4 4 4 4·I 0·22
3·5 4'5 4·5 4·5 4 4·2 0'45
4 4·5 4 4 4 4·1 0·22
3·5 0·61
3 4·5 4 3·5 3
Biting texture h
Overall score
30·5 30 30'5 31 30·5
36·0 40·0 36·0 35·5 34·3 36·4 2·15
30·6 0·6
Mean S.D•
4·5 4S 4S 3·58 4S
3 4·5 3·5 3 2·5
4 4·5 3·5 4 4
3
3·SS 0'5
4·0S 0-4
3-3 0·8
4·0 0'4
3·2 0'3
• For details of scoringprocedure,seeExperimental. b Keepingquality (k) not judged.
3 3·5 3 3-5
tTl
>-l .0
e >t'"'
~ 'Tl
0
;;0
'Tl
t'"'
>-l 0;1
;;0 tTl
>-
U C/)
C (strong) 3S 3S 3·5S 4S 4S
~
;r:
3 2'5 3 2·5 2·5 2-7 0·3
4 4 3·5 4 3-5 3·8 0'3
3 3 4 3 2·5 3·1 0·6
4·5 4·5 4 3·5 4 4·1 0·4
32 33 32·5 30-5 30·5 31·7 1·2
tV
0
v.
tv
o
'"
TABLE IV. Summaryof ANOVA for all parametersof baking test"·b Quality category Parameter C
a
b
c
d
e
64,0** 1·7NS 0·22 6'1 0·2
9,9** 5,8* 0·21 5·4 0·5
0·2NS I·ONS 0·43 10-4
J7NS 0·2NS 0·43 13-4
f
g
h
j
2·4NS ]·8NS 0·27 7,]
6'7* 0·8NS 0·37 10·4
0·2NS 4,0* 0·21 5·3
Overall score
:-0 (")
~
VR Wheat lines VR Replicates SE/test CV LSD (P = 0'05)
17'7** 0·8NS 0·32 9·0 0·6
-
8,2* 2·5NS 0·3] 9·4 0·6
0·7
28'9** ]·7NS 0·97 3·0 1·9
" 'Keepingquality' not included. b p = 0'01**, P = 0'05*. C VR = varianceratio; SE = standarderror; CV = coefficient of variation; LSD = leastsignificant differencein score;NS = not significant.
rr
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WHEAT QUALITY FOR FLAT BREADS
207
TABLE V. Two-layeredflat breadbaking perfonnanceof flours from five different wheatlines"
Wheat Ib
2 3 4 5 6 LSD"
a
b
3'5 5 3 4 2W 1·5W 2·5W 2W 3'5S 4S 4 5 0·6 0·2
c
d
e
f
g
3·5 3·5 4 4 3'5 3·5 0·5
4'5 4
4 4 2'5 3·5 3'5 4
3·5 2'5 3'5 3 3·5 4 0·6
3 4·5 4 4 3'5 4
2·5
3 3'5 5
h
j
4 3 4 4 3·5 4 4 4 4 4 4·5 4 0·7
Overall score Rank 34 33·5 27'5 30'0 33 38 1·9
2 3
6 5 4 1
• Not judgedfor keepingquality (categoryk). h Commercialflour. e Leastsignificantdifference(P = 0,05), basedon ANOVA data.
Conclusions A procedureis describedfor the evaluationof laboratoryandcommercially-milledflours by the baking of Syrian-type two-layered flat breads. Baking is carried out using commercial-typelocally madeequipmentincluding a 'wishbone'mixer, sheetingrolls and kiln-type oven. Breadsare judged on ten parametersincluding dough handling properties, crust and crumb appearance,organoleptic characteristicsand keeping quality or potentialshelf-life. The baking andjudging proceduresare reproducible,and very useful for evaluationof flat breadbakingquality in commercialflours and flours producedfrom breedingand other applied researchprogrammes.Flours of medium dough strength provided two-layered yeasted flat breads with the best overall combinationof dough-handling,appearance,c rumb and organolepticcharacteristics.
References 1. EI Saied,H. M. and EI Fana,A.-H. A. Cereal Chern. 60 (1983) 131-134. 2. Rubenthaler,G. and Faridi, H. A. Cereal Chern. 59 (1982) 72-73. 3. Faridi, H. A. and Rubenthaler,G. L. Cereal Chern. 60 (1983) 74-79. 4. Tabekhia,M. M. and Toma, R. B. Nutr. Rep. Int. 19 (1979) 377-382. 5. Dalby, G. Baker'sDig. 37 (1963) 74-77. 6. Faridi, H. A., Finney, P. L. and Rubenthaler,G. L. Cereal Chern. 58 (1981), 428-432. 7. Finney, P. L., Morad, M. M., Pattel, K., Chaudhry,S. M., Ghiasi, K., Ranhotra,G., Seitz, L. M. and Sebti, S. Baker's Dig. 54 (1980) 22-27. 8. Williams, P. C. Rachis, 2 (1983) 21.
Evaluation of Wheat Quality for the Baking of Syrian-type Two-layered Flat Breads P. C. WILLIAMS*, FOUAD JABY EL-HARAMEINt, and JIT P. SRIVASTAVAt
w. NELSONt
* Grain ResearchLaboratory, CanadianGrain Commission,1404-303Main Street, Winnipeg, Manitoba, Canada R3C 3GB and t ICARDA, P.O. Box 5466, Aleppo, Syria Received21 April 1987 A procedureis presentedfor the evaluationof wheatquality by the bakingof Syriantype, two-layeredflat breads.A detailedsystemof scoringthe breadsis discussed.T he scoring systemis basedon dough-handlingpropertiesat dividing and sheeting,the crumb colour and texture, the eatingtexture,flavour and aroma,and the regularity in appearanceof the final product. The resultsof replicatebaking of flours of weak, mediumand high strengthshowedthat the precisionof the test wassatisfactory.The procedurewas further illustratedby the baking of flours of severaladvancedlines of wheat,using a Syrian local commercialbaker'sflour as a control. The study verified that flours of medium strength tend to produce the best type of two-layeredflat breads.
Introduction During the past10 years,severaltypesof flat breadhavereceivedthe attentionof cereal scientists.The factors involved with baking Egyptian baladi breadl - 6 and Iranian and other Arabic type breads7 have beendiscussed. Arabic, two-layered,flat (2LF) breadsor 'khobz' differ from conventional raised breadsin their very characteristicshapeand texture,andfrom single-layeredbreads,of which many versionsexist. The procedurefrom mixing to baking is essentiallysimilar to that of raisedbreadsexceptfor the productionof the final flat dough piecesand the high oven temperatureat baking, which is in part responsiblefor the formation of the two layers. During primary fermentationthe dough fermentsand developsto give the familiar spongyappearance,texture and smell. The short relaxationperiod, or interproofbetweendividing and roundingandsheetingis importantsinceit hasa significant effect on the crumb texture of the final bread. When the dough enters the oven at 450 DC, the millions of minute gas bubblesthat have re-formedafter sheetingexpand very rapidly, causing the dough to inflate to a balloon-like appearance.W hen the 'balloon' burstsunderthe pressureof the expandinggasesinside,the top half collapses onto the bottom half to give the familiar two layers. In traditional Egyptian baladi Abbreviations used: 2LF = 2-layered flat (bread): ICARDA Researchin the Dry Areas. 0733-5210/88/020195 + 13 $03.00/0
= International Center for
Agricultural
© 1988 AcademicPressLimited
196
P. C. WILLIAMS ET AL.
bread, which is baked from high moisture (75-90% water absorption)doughs, the formation of steamalso contributesto the separationin the oven. Single-layeredflat breadsdiffer in several ways:they are bakedmainly from very high (up to 100 %) extraction flours, they are usually either fermentedby a sour-doughmethod or are essentiallyunfermented,a ndthe bakingtemperatureis significantly lower. As a resultof the combinationof all threefactors the gasbubble complexis not presentto the same extentin the doughs,and this, combinedwith the lower baking temperature,doesnot promotethe formation of the two-layeredstructure. The best types of 2LF breadshave a fine 'crumb' causedby the developmento f tb.e many small bubblesof carbondioxide during the final proof. The 'crumb' is the inner wall of eachlayer. The breaditself is densesincethe layers are essentiallysolid, but of a pleasant' al dente'type of biting texture.The correctcombinationof formulation and fermentationhasa critical influenceon the quality of the bread,andindividual bakeries differ widely in the quality and customeracceptabilityof their products. During 1980-1982a surveyof over fifty 2LF breadbakeriesin threecountries(Syria, Lebanon and Jordan) was carried out by the ICARDA (International Center for Agricultural Researchin the Dry Areas)cerealimprovementprogramme.A wide range in formulae and procedureswas encountered,and the resultsare summarizedin Table I. The mixers usedwere either of the wishbonetype (most widely used),swinging arm, or spiral mixers (usually in automaticbakeries).In only a few caseswere temperature
TABLE 1. Summaryof practicefor baking two-layeredflat breadsin Syria, Lebanonand Jordana Range High Ingredients(% of flour weight): Flour Water Yeast(dry) or: Yeast(compressed) Salt Sugar Procedure: Mixing time (min) Fermentationstandingtime (min) Divide: weight (g) Interprooftime (min) Sheetingthickness(mm) Final proof time (min? Baking time (min) Temperature(0C)
100 70 0·5 5
1·5 3
35 60 300
20 3 40
3 500
Low 100 40
0·15 1'5 0'3
o
8
10 195 5 1'5
o
0·5 300
• Figures are necessarilyapproximate,since most bakers measureingredients by volume in various receptacles,r ather than by weight. b Dough piecesare sheetedin two directionsbetweenintermediateand final proof.
WHEAT QUALITY FOR FLAT BREADS
197
and humidity controlledduring fermentationor proofing. Ovenswere usuallyoil-fired, but occasionallywood-fired, and temperaturecontrol was achievedby regulating the flow of oil, or by stoking (of wood burning ovens). Syria, Lebanonand Jordanare net importersof breadwheats,either as wheator as flour. In SyriaandJordan,flours milled from local breadanddurumwheatsareblended with imported('zero' flours), or with flours milled from importedwheat.Consequently, the bakersare faced with frequentchangesin the behaviourof the flours. In Lebanon, very little wheatis grown, andnearlyall flours aremilled from importedwheat(usually from Canadaor the U.S.A.). Importsby the 22 countriesof North Africa andWestAsia (including Afghanistanand Pakistan)haveincreasedby 190 % between1972-82, from 4·9 million to 14·2million tonnes,andareprojectedto reachwell over 100million tonnes by the end of the century.In view of thesefigures (basedon United Nations Food and Agriculture Organization(FAO) estimates),it is essentialt hat stringentefforts be made to increasethe productivity of cereals,andwheatin particular,throughoutthis region, which hasa rapidly growing populationof closeto 400 million. It is equally important thattheincreasein productivityof wheatis basedon varietiesthat areacceptableto both the processingindustry and the consumer,sinceif this is not so, the ensuingincreasein wastagewill tend to offset the increasesin productivity. ICARDA has establisheda laboratory in Aleppo, Syria for the evaluation of germplasmof the breadwheatand durum wheatbreedingprogrammes.B oth types of wheat are used for baking flat breads. This report describesthe experimental2LF breadbaking procedureand factors used in judging the dough strength and overall baking quality.
Experimental At ICARDA, all advancedlines of breadand durum wheatsand triticale aremilled into flour on a Buhler Model MLU 202 laboratorymill. Flour extractionis calculatedfrom the total of all six flour streamstogetherwith flour from the bran finisher, on the basis of the original tempered wheat. The flours are tested for water absorption and dough strength with a Brabender Farinographusing the 50 g bowl. Absorption is taken as the amount of water taken to give a doughwith a consistencyof 500 BU at peakdevelopmenttime, using 50 g of flour on a constant (14 %) moisturebasis. Baking quality is testedby baking commercial-typeSyrian 2LF breads ('khobz'). A small-scale,wishbonemixer (Fig. 1) was designedand madelocally by an engineeringfirm in Aleppo. The optimumcapacityis about600 g flour. The wishbone-typemixing armsrotateat an angleto the bowl, which turns freely on a spindle.The doughis forced againstthe wall of the bowl by the action of the mixing arms,causingthe bowl to rotate continuouslyduring mixing. Doughsaredivided by handandscaled.Thesheetingrolls weremadein Aleppo, andareidentical with the equipmentsuppliedto small bakeries.Doughsaresheetedin two dimensions.The dough balls arefirst rolled into a long flat oval doughpieceabout8 mm thick. Thesearepassedthrough the secondset of rolls and sheetedto round piecesof up to 2 mm thick and 28-30emdia. They emergeonto a canvasbelt, which canbe stoppedby slight pressureof the handto transferthe flat dough piecesonto a board for final proof. The ovenis a traditional type of bakeryovenor 'fourn' built at theTel HadyaResearchCentre, Aleppo, by a stonemason,whosespecialityis building bakeryovens.This enabledbakingquality • to be evaluatedby a procedureconforming closely to local and regional baking practice. A schematicdiagramof the oven,which is fired by a mazout(fuel oil) burner,is givenin Fig. 2 (full details of the constructionof the 'fourn' are availableby request).
198
P. C. WILLIAMS ET AL.
FIGURE 1. Action of 'wishbone'mixer.
TABLE II. ICARDA baking procedurefor two-layeredflat bread
Amount Ingredients Flour Yeast (compressed)" Salt Sugar Water (30°C) Procedure Mixing time Primary fermentationtime Divide Interproof time Sheetingthickness Final proof time Baking time Oven temperature
600 g
9g 6g 6g 330 ml"
% (flour weight basis) 100 1·5 1·0 1·0 55
10 min in 'wishbonemixer' 45 min 200 g 10 min "5-2 mme 25 min 35-50 s 450--470°C
• If dried yeast,3 g (0'5 %) is used. b Water addition varies accordingLo Farinographcharacteristics.Weak flours are baked at 50% water absorption.Wateris addedin incrementsof 2 % up to 60 %, which correspondsto about70 % Farinograph absorption. C Strongerdoughsare sheetedthinner.
WHEAT QUALITY FOR FLAT BREADS
[99
::.:.:::..•••••:::.:,'::. A :,,:.:.:::;;{.:,: :'::'.: I I
(0)
E
Q
( b)
FIGURE 2. Diagramsof baking oven (a) front and(b) overhead.A, absorbente arth base;B, brokenglassfilter layer; C salt insulation; D, concreteblock internal wall; E, concreteblock external wall; F, brick dome oven ceiling; G, cementlayer; H, accessdoor; J, burner; K, air space;L, basaltoven wall; M, basaltoven floor; N, flue; P, steel baffle plate; Q, limestoneslab doorway sill. The rCARDA baking test was basedon the observationsmadeduring the bakery survey. It representsa practicable'average'formula and procedure,a nd is summarizedin Table II. Baking absorptionis varied in incrementsof 2 %, accordingto Farinographabsorption.For optimum dough-handling,baking absorptionwas found to be 4-8 % lower than Farinographabsorption (50 g bowl). Flourswith Farinographabsorptionof 56-57% hadgooddough-handlingproperties at about52 % bakingabsorption,whereasa flour with 68-70% Farinographabsorptionhandled well at 60-62% baking absorption.
200
P. C. WILLIAMS ET AL.
The standardformula canbe changedto accommodatemoreor lessflour; otheringredientsare then recalcu.1atedon a percentagebasis.Doughsare mixed in the wishbonemixer using water at about30 °e, then coveredwith a cloth and a plasticcoverto maintainthe relative humidity, and kept at 25 ± 2 °e. Thesefermentationconditions simulate, but are superior to, those of most commercialbakeries,whereseasonalfluctuationsin the ambienttemperaturearecompensatedfor by adjusting the formula and fermentationconditions. Sugaris sometimesusedin commercial bakeriesto acceleratefermentation,and salt to retardit. At ICARDA, doughstrengthis judgedat the dividing andsheetingstages.The total weight of dough preparedallows for four, full-sized (200 g) dough pieces (loaves), with a small piece (130-150g) left over. This small piece is rounded and inter-proofed in the normal way, and usedto test the sheetingconditions.The rolls are set accordingto the behaviourof this dough piece.If the small or 'pilot' doughis very strong,the rolls areadjustedto give a thinnerfinal dough piece, or a slightly thicker one if the dough appearstoo weak; this is the systempractisedin commercialbaking. After sheeting,the flat doughsare placed on boardsfor final proofing. Both intermediate and final proofing are carried out under the same temperatureand humidity conditionsas the primary fermentation.The doughsarebakedat about450 ± 10 °e. Baking time is 40-50 s. Thefinal2LF breadis cooledfor about10 min, temporarilystoredin plasticbags,and judgedthe sameday. Threeloavesarejudgedfrom eachbake.The fourth may be usedto judge keeping quality: it is placedin a plastic bag and left overnight at room temperature.I t is then folded tightly. The patternof crackingis a measureof keepingquality, and a further indication of strength.Baking at optimum water absorptionfor the flour is critical to the keepingquality test.
Judging and scoring Judgingis, by nature,subjective(exceptfor diametermeasurement),andjudging of threeor more loavesreducesthe risk of errorsin judgement.Doughsfor determinationof specificcharacteristics and genotypesintended for advancementto national programmesare preparedat least in duplicate,so that judgementsare basedon six or more loaves.The arbitrary numerical scores given for particularquality traits are given at the end of eachsection(scoresfor eachare 1-5). a and b. Dough handlingproperties. Thesepropertiesat dividing and sheetingare very important in 2LF bread baking, sinceif dough handling propertiesare poor the flour causesproblemsin bakeries.Most of the bakeriesin the Middle Eastcall for fairly extensivephysicalmanipulation of the thin, flat doughpiecesbetweenmixing and baking, particularly in automatedbakeries.If doughsare too weak, they becometoo thin at sheetingandholesdevelop.Very weakdoughsfall betweenthe fingers in manual bakeries,and causeseriousproblems in sheetingin automatic bakeries.On the otherhand,very strongdoughswith high elasticityshrink aftersheetingand give thick loaveswith poor textureand 'biteability'. Whenvery weak doughsaresheetedthinly, they becometough and 'chewy' in baking and less attractive to the consumer.Weak doughs also becomestale and hardenmore quickly than strong doughs.Dough-handlingat dividing gives a goodindicationof baking(water)absorption,andflours with very poor handlingat dividing may be re-bakedat different water absorption.
Scoring (a) Dough handling at dividing: 1W, Very weak, sticky and difficult to mould; or IS. Very stiff anddifficult to form a ball without cracking.2W, Weakand difficult to mould; or 2S stiff and difficult to mould. 3, Fair handling. 4, Good handling. 5, Very good, 'lively' feel. Scoring(b) Doughhandlingat sheeting:1W, Very weak and fragile, not possible to obtain good intact dough piecesevenafter resheetingat 2·0 mm. 2W, Weak and fragile, remouldingand resheetingnecessary.3W, Fair handling. 4, Good handling. 5, Very good handling properties.Alternative: 18, Excessivelystrong (i.e. excessive elasticity),doughpiecesshrink evenafter resheetingat 1·0 mm. 28, Very strong(too muchelasticity),doughpiecesneedresheetingat 1·0 mm. 38, Strongerthanoptimum but nO resheetingnecessary.
WHEAT QUALITY FOR FLAT BREADS
201
Differences between'fair' and 'good', 'good' and 'very good', etc., are subjective,and are evaluatedby comparisonwith flours of known, professionally-evaluated bakingperformance. c. Colour andappearance.Off-coloursand burnt patchesarevery noticeableon the surfaceof flat breads.Grey colour can be causedby foreign materialon the outsideof the grain beforemilling, by the milling operationitself, by small amountsof oil extrudedfrom the mixer, by fungal spores and by other agencies.Several commercial flour mills have been installed very recently, in Northern Syria, and they mill to 80 % extraction. In addition, bunt (Tilletia caries) is very prevalentin the regionS,so that grey is the off-colour mostfrequentlyencountered.Nevertheless, the doughstrength,diameterandcrumb textureenablean evaluationof the inherentstrengthof a flour. Burnt patchesusually indicate inadequatefermentation,over-fermentation,or high aamylaseactivity. Ideally 2LF breadshouldbe of an evencreamto pale brown colour, with no patches.2LF breadbakedfrom durum flours or flours with a high proportion of durumtend to be yellow. Scoring; 1, Grey, yellow or very burnt, or holes. 2, Lighter grey or yellow, less burningor holes.3, Paleto white, patchesapparent.4, White to paleyellow or pale yellow/brown. No burnt patches.5, Pale to light brown colour, even colour over whole loaf. d. Diameter. For a 200 g doughpiecethis shouldbe about28-30em. If doughis too strong, the diametercan be as little as 15-20em; if the dough is too weak, it can be 35-40em, with holes. Diameteris measuredin two dimensionsand the ratio of one diameterto the other calculated. Pointsare subtractedfrom the scoreif the loaf is not round. Regularityin the roundnessof 2LF breadloavesis alfectedby the efficiency of roundingthe doughpiecesat the dividing stage,but mainly by the two-dimensionalsheeting.Weak doughstend to stretchso much during the first sheetingthat they do not resumeroundnessat the secondsheeting.Very weak doughsmay have to be re-rounded,relaxedand re-sheetedbefore a bakeabledough piece can be achieved.This affects the crumb textureof the final bread.
Scoring; Diameter lW, Above 36 mm with holes 2W,34-36mm 3W,32-34mm 4W,3D-32mm 5,28-30mm 4S, 25-28mm 3S, 22-25mm 2S, 19-22mm IS, less than 19 mm
Ratio
Points subtractedfrom score
1; 1·05 1; 1·15 1: 1·25 1: 1·35 1; 1'45 1: 1'55
0·5 1·0 1'5 2·0 2'5 3'0
e. Crumb texture. Internal crumb should be rich in smail cens 1-2 mm in diameter, evenly distributed about both internal surfaces.Large-celledstructureis referredto as coarsetexture. Sometimesthe internal crumb is waxy, which meansthat there is no cell structure.Another characteristicis that layers may not part evenly. When this happens,somepartsof the internal surfacewill havegood cell structure,and other partswill have no cells, but will appearto have a 'waxy' surface.Texture is strongly affected by fermentation,and poor texture is usually an indicationof under-or over-fermentation(Fig. 3). It is alsoaffectedby the sheeting.If the dough pieceis too thick, the cells of the final loaf will be large,with thick cell walls. This is often the case if the doughsare too strong.They contractafter sheetingto give a thicker doughpieceandpoor, coarsetexture.
P. C. WILLIAMS ET At.
202
. ....
(a) " ~.'
FIGURE 3. Crumb texture of two-layeredflat bread Ckhobz'): (a) excellent; (b) coarse,open (poor); (c) very good; (d) waxy, indicatespoor fermentation.
WHEAT QUALITY FOR FLAT BREADS
203
Scoring: 1, Densewaxy texture, no visible cells. 2, Waxy texture, somecells. 3, Moist appearance,smaller cells. 4, Moist, large patchesof small uniform cells. 5, Moist, small, uniform cells, crumb even, with no patches.Alternative: IC, Very coarseopentexture,very largecells(usuallyassociatedwith loavesof smalldiameter). 2e, Coarseopen texture, large cells.
f Separation.Separationof the two layers should be even, and each layer should be about 1'5-2'2 mm thick. Frequentlyone layer will be thicker than the other. This candevelopduring proofing, dueto bubblesof gasforming closerto onesurfacethan the other. It canalso becaused by ovenconditions.If the ovenis too hot at the floor level, the bottomlayerwill be thin, and often burn. At the sametime, the other layer will be too thick and will have poor crumb texture and 'biteability'.
Scoring: I, No separation,o r only partial separation.2, Very unevenseparation, one layer less than I mm. One layer over 3 mm. 3, Uneven separation, 2 mm difference betweenlayer thickness.4, Even separationacrossmost of loaf. 5, Even separationin all areas. g. Smell.Smellsor odoursarecausedby small amountsof aromaticsubstancessuchas estersor ketones,or by burningand caramelizationof sugars.Moulds may also causeodours.Smell is an importantcomponentof taste,and should be judged separately. Scoring(smellsshould be identified if possible):I, Very strongsmell of 'burnt' or other taints. 2, Definite smell of 'burnt' or other taints. 3, Faint smell of 'burnt' or other taints. 4, Bland smell, no identifiable substances;5, Positive pleasantsmell of 'fresh bread'. h. 'Biteability'. This is testedby biting the bread.2LF breadmay be soft, chewyor sticky, tender
Cal dente'),toughandleathery,or hard.Theseconditionsreflectpropertiesof the flour, sincethey arecausedby a combinationof partial starchgelatinization,watercontentat baking, andprotein denaturationduring baking. If the protein contentof the flour is high andstarchdamageis low it is likely that the resultant bread will be tough or heavy to bite. On the other hand, highly damagedstarchabsorbsa lot of waterand leadsto a higherdegreeof starchgelatinization, giving a softercrumb. 2LF breadbakedfrom puredurum flours havea softer texturethan thosebaked from breadwheatflour, andin general,the softerthe wheat,the harderandmore'cardboard-like' are the bakedloaves. Scoring: 1. Very tough leatheryfeel; hard to chew. 2. Tough. 3. Very sticky when chewing. 4. Slightly sticky when chewing. 5. Pleasantand easy to chew, 'al-dente' type. 4S. Soft and less 'body'. 3S. Very soft. j. Taste. 2LF bread should tasteof the ingredientsafter they have undergonemodification by
fermentation,and the heat of the oven. Most flours give loaveswith acceptabletasteand smell. Off flavours can be causedby acid developmentduring fermentation,by moulds,too much yeast or salt, too much sugar(which will causecaramelizationand burning), and by burning itself. Mouldy, tainted or otherwisedamagedflours can also impart poor flavour and aroma. Scoring: I, Very poor taste due to off-flavours or burning, difficult to swallow, strong and unpleasantafter-taste.2, Poor taste due to off-flavours or burning. Unpleasantafter-taste.3, Fair taste. 4, Good taste. 5, Excellent taste, and after taste. k. Keepingquality. Flourswith poor strengthusually will retain the textureof the 2LF breadonly for a shortwhile after baking. If a loaf is folded tightly it will tear andmay breakup completely. Othersmay not crack at all, and theseare referred to as strong.
204
P. C. WILLIAMS ET AL.
Scoring: 1, Breadpiecesdisintegratecompletelyon folding. 2, Heavy tearingover all areas.3, Tearingat centreandadjacentto centre.4, Slight tearingnearcentreonly. 5, No cracking, khobz completelyresistantto tearing.
Overall score The overall total possiblescoreis 50, with the highest total scorebeing the best. This method enablesthe bakerto detectwhy individualflours vary. In anysetof flours tested,a particularflour may havea low overall scorebecauseof one bad characteristiceventhoughit is goodin others. This one badcharactercould causedifficulties in commercialbaking, and it would be important to identify sucha factor beforea variety becomeslicensed.The systemis also helpful to breeders, particularly when the progenyof wide crossesare being evaluated.
Results and Discussion
To determinethe reproducibility of the bakingprocedure,threedifferent Buhler-milled flours were used. Five replicateswere baked, and the fifteen doughsrandomizedfor bakingand also for judging. The resultsof baking thesethreeflours aresummarizedin TableIII. Theflours differedconsiderablyin strength.TheaverageFarinographstability of the weaker flour was 3·2 min, and the medium strength and stronger flours respectively6·3 and 12·7min. Extractionof the flours was respectively72, 76 and 75 %. Precisionfor scoring the nine characteristicswas good and the overall precisionof the bakingscorewas 0·97 pointsfor a coefficientof variability (CV) of 3·0. Leastsignificant difference betweenmeansfor baking scorewas 1·9 points (P = 0,05). The analysisof variancefor eachparameteris summarizedin Table IV. Most flours gave breadwith reasonableto very goodtasteandsmell. Theparametersfor which differencesweremost clear-cutwerethe doughstrengthat dividing and at sheeting,the biteability andcrumb texture,the colour andthe overall score.Differencesin doughstrengthat sheetingwere very noticeablebetweenthe three flours. This is a particularly critical factor in both manual and automatic 2LF breadbaking.The results also indicated that, for 2LF breadbaking,the medium-strengthflours were generallysuperiorto either strongeror weaker flours. Stronger flours were superior to weaker flours in dough-handling properties,but inferior in crumb and separationcharacteristicsand biting texture,due to the increasedthicknessof the final dough piece. Medium-strengthflours were wellbalancedin all parameters. TableV illustratesthe resultsof applyingthe abovebakingandscoringprocedureto five unknownwheatlines (2-6), with a commercial,80% extractionflour as a control. All the test flours were Buhler-milled from advancedbread wheat lines from the ICARDA cereal programme. Extraction rate varied from 72 to 76%. Clear-cut differenceswere apparentbetweenthe lines, with No.2 being the poorestin several categories.N umber6 was consistentlyscoredhighly, and was equalor superiorto the commercialbaker'sflour in all parameters.Differencesbetweenflours in flavour and aromawerestatisticallyinsignificant. The scoringof theseorganolepticparametershas little practical value unlessthe baking procedureis to be applied to a study involving changesin baking formula. such as salt or sugar content, or to tainted or otherwise damagedflours.
TABLE III. Quality evaluationscoresand reproducibility of bakingprocedurefor two-layeredflat breadfrom flours of different strengths"b Dough handling
Flour
Mean S.D.
Mean S.D.
Dividing a
Sheeting b
3·5 2·5W 3W 2·5W 3W
2·5W 2·5W 2W 2W 3W
2·9 0·4
2-4 0·4
4·5 4 4'5 4·5 4
4·5 4 4·5 4·5 4·5
4·3 0·27
4·4 0'22
Colour
c 4 4·5 4 4 4 4·1 0·2 4 4·5 4 4 3'5 4·0 0·35
Diameter Separation Crumb Aroma d e f g
4·5 3·5 3·5 4·5 5 4·2 0·7 4·5 5 3·5 3·5 3·8 4·1 0·67
A (weak) 2 2·5 2·5 3·5 3 2·7 0·6 B (medium) 4 4·5 3·5 3 3·5 3·7 0·57
3·5 4·5 4 3·5 3
3·5 3 3 4 3·5
Taste
i
3·7 0·6
3-6 0·7
3-4 0·4
4 4·5 4·5 3·5 3'5 4·0 0·5
3W 4'5 3·5 3·5 3W
4 4'5 4 4 4 4·I 0·22
3·5 4'5 4·5 4·5 4 4·2 0'45
4 4·5 4 4 4 4·1 0·22
3·5 0·61
3 4·5 4 3·5 3
Biting texture h
Overall score
30·5 30 30'5 31 30·5
36·0 40·0 36·0 35·5 34·3 36·4 2·15
30·6 0·6
Mean S.D•
4·5 4S 4S 3·58 4S
3 4·5 3·5 3 2·5
4 4·5 3·5 4 4
3
3·SS 0'5
4·0S 0-4
3-3 0·8
4·0 0'4
3·2 0'3
• For details of scoringprocedure,seeExperimental. b Keepingquality (k) not judged.
3 3·5 3 3-5
tTl
>-l .0
e >t'"'
~ 'Tl
0
;;0
'Tl
t'"'
>-l 0;1
;;0 tTl
>-
U C/)
C (strong) 3S 3S 3·5S 4S 4S
~
;r:
3 2'5 3 2·5 2·5 2-7 0·3
4 4 3·5 4 3-5 3·8 0'3
3 3 4 3 2·5 3·1 0·6
4·5 4·5 4 3·5 4 4·1 0·4
32 33 32·5 30-5 30·5 31·7 1·2
tV
0
v.
tv
o
'"
TABLE IV. Summaryof ANOVA for all parametersof baking test"·b Quality category Parameter C
a
b
c
d
e
64,0** 1·7NS 0·22 6'1 0·2
9,9** 5,8* 0·21 5·4 0·5
0·2NS I·ONS 0·43 10-4
J7NS 0·2NS 0·43 13-4
f
g
h
j
2·4NS ]·8NS 0·27 7,]
6'7* 0·8NS 0·37 10·4
0·2NS 4,0* 0·21 5·3
Overall score
:-0 (")
~
VR Wheat lines VR Replicates SE/test CV LSD (P = 0'05)
17'7** 0·8NS 0·32 9·0 0·6
-
8,2* 2·5NS 0·3] 9·4 0·6
0·7
28'9** ]·7NS 0·97 3·0 1·9
" 'Keepingquality' not included. b p = 0'01**, P = 0'05*. C VR = varianceratio; SE = standarderror; CV = coefficient of variation; LSD = leastsignificant differencein score;NS = not significant.
rr
;;
3:: en
..
tl'J .....,
r--
WHEAT QUALITY FOR FLAT BREADS
207
TABLE V. Two-layeredflat breadbaking perfonnanceof flours from five different wheatlines"
Wheat Ib
2 3 4 5 6 LSD"
a
b
3'5 5 3 4 2W 1·5W 2·5W 2W 3'5S 4S 4 5 0·6 0·2
c
d
e
f
g
3·5 3·5 4 4 3'5 3·5 0·5
4'5 4
4 4 2'5 3·5 3'5 4
3·5 2'5 3'5 3 3·5 4 0·6
3 4·5 4 4 3'5 4
2·5
3 3'5 5
h
j
4 3 4 4 3·5 4 4 4 4 4 4·5 4 0·7
Overall score Rank 34 33·5 27'5 30'0 33 38 1·9
2 3
6 5 4 1
• Not judgedfor keepingquality (categoryk). h Commercialflour. e Leastsignificantdifference(P = 0,05), basedon ANOVA data.
Conclusions A procedureis describedfor the evaluationof laboratoryandcommercially-milledflours by the baking of Syrian-type two-layered flat breads. Baking is carried out using commercial-typelocally madeequipmentincluding a 'wishbone'mixer, sheetingrolls and kiln-type oven. Breadsare judged on ten parametersincluding dough handling properties, crust and crumb appearance,organoleptic characteristicsand keeping quality or potentialshelf-life. The baking andjudging proceduresare reproducible,and very useful for evaluationof flat breadbakingquality in commercialflours and flours producedfrom breedingand other applied researchprogrammes.Flours of medium dough strength provided two-layered yeasted flat breads with the best overall combinationof dough-handling,appearance,c rumb and organolepticcharacteristics.
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