Journal ofCerealScience4 (1986) 261-268

The Effect of Alkaline Conditions on the Properties ofWheat Flour Dough and Cantonese-styleNoodles

H. J. MOSS,D. M. MISKELLY and R. MOSS

BreadResearchInstitute ofAustralia, North Ryde,NSW2113,Australia

Received9 December1985

NaCl, two blendsof Na2COa and K 2COa, and NaOH wereeachincludedin wheatflour doughs. Their effects on dough properties as measuredby a BrabenderFarinographand Extensograph(at reducedwater absorption)and by a Viscographwere assessed.Cantonese-stylenoodleswere then made from the correspondingdoughsandthe raw andcookednoodleswereexamined.

Addition of alkali resultedin noodlesthatwerea little brighterandmuchyellowerthannoodlesfrom salteddoughs.The brightestandyellowestwereat thehighestpH(11'4).Alkaline doughsdevelopedandbrokedown morerapidly in theFarinograph,andweretougherandlessextensiblein theExtensographtest.With 1% NaOH(flourweight basis), thickening was acceleratedand peak paste viscosity was greatlyincreased.With O' 3% NaOH,or themixturesofcarbonates,thickeningwasretardedbut pasteviscosity increased.

The 1% NaOH gave the brightestand yellowest boiled noodles,but they wereslightly sticky. The boilednoodlesfrom otheralkalinedoughswerefirmer andmoreelasticthan thosemadewith NaCI or with 1% NaOH. Microscopicexaminationofthe raw noodledoughsindicatedthat the addition of 1%NaOH adverselyaffectedglutendevelopment.After cooking,thestarchgranulesin the 1%NaOHnoodleshadswollento a greaterextentthan in the othernoodles,the proteinnetworkwasmoredisruptedandlargervoid spaceswereseenin thecentreof the noodles

Introduction

Cantonesenoodlesarecommonlyconsumedin South-EastAsiaandJapan.Theessentialingredientsareflour, waterandalkalinesalts.Thesesaltscanbe sodiumor potassiumcarbonateorbicarbonate- evensodiumhydroxidemaybeused.Theseagentsareknownby namessuchas 'lye water' or 'kanswi' ('kan sui').

Becauseof thenatureof theingredients,theraw productis quitealkalineand,in fact,the pH is normally between9 and 11. This contrastsstronglywith mostotherfoods orfood processeswhich are in the acid to neutral rangel . Becausevery few otheralkaline foodstuffs areconsumed,only limited information is availableon foods withpH valuesabove7, particularly in relation to doughproperties.Someeffectsof alkalion wheatstarchextrusioncookinghavebeendescribed2•

The alkaline saltsconfera uniqueflavour andquality to Cantonesenoodlesandareresponsiblefor their yellow colourwhich developsunderalkalineconditions,dueto theflavonoids presentin the flour3• Alkaline salts toughenthe dough4 and affect pasting0733-5210/86/030261+08 $03.00/0 © 1986AcademicPressInc. (London) Limited

262 H. J. MOSSETAL.

properties4 , 5, as well as inhibiting enzymeactivity andsuppressingenzymicdarkening.Alkaline treatmentsalsocauseisomerizationofaminoacids,desulfurationofcysteineanda decline in the biological availability of lysine and dehydroalanine(resulting fromdesulfurationof cysteine)which reactto form nutritionally undesirablelysinoalanine6•

Previousresearchwork in the areaof Cantonesenoodleproductionhasconcentratedon issuesconcernedwith flour quality requirementsor hasexaminedthe contributionof flour extractionrate, pigmentsand protein contentto noodle colour8• This workexamines the modification of flour properties and resultant noodle qualities anddifferencesin noodlemicrostructure,causedby variousalkalineagentscommonlyusedin commercialnoodleproductionin South-EastAsia.

Experimental

Five Australianwheatsamplesfrom the 1983harvestwereselectedfor this studyandmilled intoflour asfollows: (a) WesternAustralianHardwheatwasmilled to 60% flour extractionaccordingto the methodof the JapanWheatFlour Institute9 ; the protein contentwas 11·1% (dry weightbasis)andtheFlourColourGradewas -1,8.(b) NewSouthWalesPrimeHard,QueenslandHardanda blendofsoft wheatsgrownin WesternAustraliawereeachmilled to full extraction(straightrun flour) usingthe Buhlerexperimentmill lO • Proteincontentswere respectively12·5, 11·3 and9·3% andFlourColourGrades-0·1, -1,1 and0·2. (c) WesternAustralianStandardWhitewheatwasmilled in a commercialflour mill; the proteincontentwas9'2% andthe Colour Grade0·9.

Analytical tests

Flourswereexaminedfor proteincontentandcolour gradeby standardmethodsll.

Alkali treatments

In ordertostimulateandmeasuretheeffectsof thealkalinereagentsusedin commercialrawnoodleproduction,eachtest was carriedout so that the saltsand alkali were addedto the flour in thefollowing quantities (w/w); NaCI (1%); Na2COs (0·6%)+K2COS (0·4%); Na2COs(0·9%)+K2COS (0,1%); NaOH (0,3%) and NaOH (1,0%). The reagentsweredissolvedin thewaterusedfor thedoughs.Thesesolutionswerechosenasrepresentativeof therangeoflye watersusedin Cantonesenoodleformulations.

Flour quality

Waterretentioncapacitywasmeasuredby amethodanalogousto thatofYamazakil2 • Flourpasteviscosity and gelatinisationpropertieswere determinedusing the BrabenderViscograph, anddoughpropertiesby the FarinographandExtensograph.For the purposeof this work the startofgelatinisationwastakenasthetemperatureatwhichanextrapolationof themainupwardsweepof the Viscogramintersectedthe baseline. In the Extensograph,doughswere remixedto a finalconsistencyof 625Farinographunits.Thereagentundertestwasaddedat thestatedlevel in placeof the 2%N aCI specifiedin the standardmethodll.

Noodlepreparation

Noodleswerepreparedusingan Otakenoodlemachine.Theappropriateamountof eachreagentwasdissolvedin water(96 g),addedto flour (300 gadjustedto 13·5%moisturecontent)andmixed

ALKALINE EFFECTSON DOUGH AND NOODLES 263

in a Hobart N50G mixer. The noodlemanufacturingprocesshas beendescribedpreviously8.Essentiallythis amountsto mixing the ingredientsto a crumbly dough,combiningthe particlesby compressionbetweensteelrollers andreductionof the doughsheetto the requiredthickness.In this work a portion of the sheeteddoughwaskept for colour measurementin the HunterlabColour DifferenceMeter, and for subjectiveassessment,both on the day of preparationand onthefollowing day. In the subjectiveteststhemaximumscorewas6 for a veryclean,clear,yellow,attractiveproduct.Thedoughsheetwasreducedto afinal thicknessof 1.5mmandpassedthroughNo. 20 cuttingrolls to give stringsof 1·5mm width.

Noodle testing

Four samples(100g each) of raw noodle were placed in separatewire basketsand boiledsimultaneouslyin water (8 I) until optimally cooked.The cooking time hadbeenestablishedina preliminarycookingtest.Noodleswereconsideredto be optimally cookedwhenthegelatinisedzonehadjust reachedthe centreof the noodlestrand.

Boiled noodlesweredrainedandweighedto determineyield andwateruptake.Eatingqualitywasevaluatedby a trainedtastepanel.Pointswere allotted out of a maximumof 30- firmness(10), elasticity(10) andfreedomfrom surfacestickiness(10). Thesearethe threemostimportantquality characteristics.The higherthe score,the betterthe quality.

The pH valuesof both freshand boiled noodlesweredeterminedby dispersingnoodles(10 g)in distilled water(100 g) usingan Ultra-Turraxhigh speedhomogeniser,allowing themixture tosettlefor 30 min, thenmeasuringthe pH of the supernatantliquor.

Microscopy

Samplesof noodleswerefixed in phosphate-bufferedglutaraldehyde(pH 7) for sevendayspriorto cryostatsectioning13• Cookednoodleswere cooledfor I min in cold (15°C) tap water priorto fixation. Thesectionswerestainedwith Ponceau2R13 to demonstratetheproteindistributionorPAS/FastGreen14 todemonstratestarchandprotein.Polarising-andphase-contrastmicroscopywereusedto studythechangesthat took placein thestarch.

Resultsand Discussion

Experimental

Table I showsthe effectsof the varioussalt and alkali treatmentson flour and noodleproperties.Colourmeasurementsareshownin TableII. Meanresultsfor thefive floursareshownfor the sakeof simplicity, althoughthereweresomedifferencesin degreeofresponse.DoughscontainingNaOH becametoo sticky or difficult to handlenormally,so thatsomeExtensographtestsandwater-retentiontestshadto be abandoned.As thewater contentof noodle dough formulae is only 30%, the problemof thesedoughsbecomingsticky doesnot occur in practiceduring noodleproduction.

FromtheViscographmeasurementsit canbeseenthatO'3%alkali treatmentincreasedthe temperatureand the time at which gelatinisationbeganto occur,but 1% NaOHacceleratedgelatinisation.The peak viscosity was increasedwhen alkali was added.Figure 1 showsthe Viscogramsobtainedwith flour milled from PrimeHardwheatforthreeof thesix treatments.Thecontrastingeffectof 1%NaOH,comparedwith theotheralkaline treatments,is not surprisingin view of the relationshipof starchviscosity toalkalinity at pH 1215,

264 H. J. MOSS ETAL.

TABLE 1. Propertiesof doughandnoodlespreparedfrom variousflours with salt oralkali treatment

Na2C03 Na2COS

Addition to dough NaCI +K2COS +K2COS NaOH NaOHconcentration 1% 0·6% +0'4% 0'9% +0'1% 0'3% 1-0%(% of flour weight)B

Waterretention 70·7 87·2 81·2 83·9capacity(%)

ViscographdataStartof gelatinisationb

time (min) 33·0 34·5 3509 36·7 28·0temperature(0e) 79·5 82 84 85 72

Pastingpeak(AU)C 784 1233 1240 1089 1785time (min) 40·6 43·2 43-1 42·9 37·5temperature(0e) 91 95 94·6 94·3 86

FarinographdataWaterabsorption(%) 59·8 62·0 61·4 67·6 70·9Developmenttime (min) 6·2 5·3 3·4 3·5 Jo4Breakdown(FU)d 53 39 60 103 155

ExtensographdataMaximum resistance 391 744 738

(Eu)eExtensibility (em) 19'7 13·5 12·9

Raw noodlepropertiespH 6·2 10·0 9·9 10·0 11·4Colour (points) 4·1 4·6 4·3 4·9 5-9Colour after24 h (points) 3-8 4·3 4·4 4-8 6·0

CookednoodlepropertiesWateruptake(%) 92 118 119 115 112pH 6·7 9·8 9·8 9·5 10·4Optimumcookingtime 2·1 4·0 4·0 4·1 4'3

(min)Colour (points)b 3·9 4·3 4-4 4·7 4·9Eatingquality (points)b 16 19 19 19 17

a Naturalmoisturebasis.b SeeExperimentalfor details.C AU, amylographunits.d FU, farinographunits.e EU, extensographunits.

Alkaline saltsincreasedtheFarinographwaterabsorptionandgenerallydecreasedthemixing requirement.Doughsbecametougherandshorter(Fig. 2). This is consistentwiththe observationsof Teradaet ai. 4. In the noodlemanufacturingprocess,the alkalinesaltsserveinitially to toughenthedough,whichthenappearsto becomeweakerandmoreextensiblewith successivepassesthroughthe combiningrolls. An analogousweakeninghasbeennotedin breaddough16•

ALKALINE EFFECTSON DOUGH AND NOODLES

TABLE II. Effect of alkaline conditionson colour (Hunterlab)of uncookedCantonesenoodles3

265

Day of preparation After 24 hoursConcentration

Addition (% offlour) Brightness Yellowness Brightness Yellowness

NaCI 1·0 74 38 66 44NaaCOa+ 0·6+0·4 75 49 68 54

KaCOaNaaCOa+ 0·9+0·1 76 49 69 54

KaCOaNaOH 0·3 75 51 68 57NaOH 1·0 77 54 72 59

a Eachvaluerepresentsthemeanof resultsfrom eachof the five different flours (seeExperimental).Significance:BrightnessP < 0·001 for treatment,day and treatmentx day; YellownessP < 0·001 for

treatmentandday; treatmentx daynot significant.

1000

.~.,." .........

!:

!:I

I!

(-'\,fI i

/ \i \

,,// .l_.... ,"

. .............60 90

Temperature (DC)

FIGURE1. Viscogramsofprimehardwheatflour showingeffectsofdifferentreagentadditions.Arrows indicatestartof gelatinisation.--, 1%NaOH;---, 1%NaCI;

....., 0·9% NaaCOa+O'I% KaCOa.

Noodle cookingcharacteristics

The alkalinenoodlesvariedbetween9·9 and11-4pH unitscomparedwith 6·2 pH unitsfor the saltednoodles(TableI). They all hada longercookingrequirementthan thosewith NaCI andhada higherwateruptake,giving a higheryield of boiled noodles.Aftercooking, thenoodlesfrom doughscontaining1%NaOHweresticky on thesurfaceand

266 H. J. MOSSETAL.

-------........../........ ", ,

//~ \\

/ \I \

! .~----T\ ------_IJ,II

500

o 5 ~

Extension (em)

FIGURE 2. Extensogramsof Western Australian StandardWhite wheat flourshowingtheeffectsof saltand'lye water'.--I%NaCI; ...., 0·9% Na2C03 +O'1%

K 2C03•

showedsignsof breakdown.This indicatesa slower advancementof the cookedzoneinto the centre of the noodle. An increasein the surface breakdownof spaghettiassociatedwith increasingalkalinity of the cookingwaterhasbeennotedby Menger17•

In addition, Dexter et al.18 found that spaghettilost more solids during cooking withincreasingalkalinity and hardnessof the cooking water. Preliminary tests, in whichnoodleswere cookedsuccessivelyin the samecooking water, confirmed that noodlesbecamemoresticky asthepH of thewaterincreasedfrom 9·0 to 9·5unitsandtotal solidmaterial in thecookingwater increasedfrom 0·27 to 0·52%.

Noodle colour

Differencesin colour of preparednoodlesresultedfrom differencesin salt or alkalineingredientsused in the formula. Thesewere highly significant, as shownin Table II.Noodlespreparedwith NaCI only were white or creamin colour, thosefrom alkalinesaltswere yellow. Noodleswith potassiumsaltsin the formula tendedto havea greenhue, thosewith sodium salts (at alkaline pH) were a clear yellow. The higher NaOH(1 %) concentrationwasassociatedwith freedomfrom discolouration,which is normallyexperiencedwith this productafter a short standingtime. It may be that the pH is, inthis case,out of the range in which the enzymesystems,which are responsiblefordarkening, are active. Other issues affecting noodle colour have been discussedpreviously8.

Microstructure

The microstructureof thecrumbly doughat the endof mixing wassimilar in all cases,but differencesbecameapparentafter the doughwas passedthrough the rollers. Thedoughcontaining1% NaOH appearedto be tougher,andmicroscopicexaminationofthe doughat the end of the compressionstageindicatedthat therewas a differenceinthe appearanceof the protein. The protein network in this dough(Fig. 3) was not ascontinuousanduniform as that in thedoughcontainingeither I % of a 9: I mixture ofNa2C03 andK 2C03 (Fig. 4) or 1% ofNaCI.TheNaOHhadpreventedtheglutenprotein

ALKALINE EFFECTSON DOUGH AND NOODLES 267

from being stretchedout adequatelyanddeveloped,and this toughnessalso preventedthe air from beingdisplacedduring passageof the doughthroughthe rollers.

During thereductionprocesstherewaslittle changein themicrostructuralappearanceof the doughscontainingcarbonatesor NaC!, hut the gluten in the NaOH-containingdoughwas developedfurther. One extrapasswasrequiredto reachthe desireddoughsheetthickness,yet the protein developmentwas not quite as uniform as that seenintheothertwo samples.Themicroscopicappearanceof thestarchat this stagewassimilarin all threesamples.This lack of change,undervery alkalineconditions,maybe relatedto the low watercontentof thesedoughs.

FIGURE 3. Sectionof a noodle doughcontaining 1% NaOH at the end of thecompressionstage.Note the lack of uniformity of thedarkly stainedproteinmatrix.(P).Someundevelopedendospermparticles(U) arealsopresent.(Stain,Ponceau2R;

Bar, 50 ~m.)

FIGURE4. Sectionof noodledoughcontainingNa2C03 (0,9%)+K2C03 (0,1%) attheendof the compressionstage.Note the uniformity of the darkly stainedproteinmatrix (P) which surroundsvirtually all thestarchgranules.(Stain,Ponceau2R; Bar,

50 (lID.)FIGURE5. Sectionof thecentralregionof acookednoodlefrom doughcontaining1% NaOH. Note the grosslyswollenstarchgranules(0), coarseproteinmatrix (C)

andrelatively largevoids (V). (Stain,PAS/FastGreen;Bar, 20 ~ID.)

FIGURE6. Sectionof thecentralregionof a cookednoodlefrom doughcontainingNa2C03 (0'9%)+K2C03 (0'1%). Note thesmallervoids(V), finer, morecontinuousprotein network (P) and relative lack of grosslyswollen or burst starchgranules.

(Stain,PAS/FastGreen;Bar, 20 J.Lm.)

268 H. J. MOSSETAL.

After the noodleswerecookedtherewerealso differencesbetweenthe threesamplesin the appearanceof thestarch.The starchgranulesin thecentreof the NaOH noodles(Fig. 5) weremoreswollenthanthosein theothersamples(Fig. 6). More of the starchgranuleshad either becomegrossly distorted or had burst. It was not possible todeterminewhetherthis was due to the action of the NaOH on the starch,or to thepoorerprotein developmentallowing more water to penetrateinto the centreof thenoodle.Therewere also morenumerousand largervoids in the centreof the NaOHnoodle.Thesevoids, togetherwith the poorerproteindevelopmentand more swollenstarch,wererelatedto the softertextureof the cookedNaOH noodle.

Conclusion

The alkalineconditionsin the preparationof Cantonesenoodlesmodified pastinganddoughproperties,affectedthecolourandcookingcharacteristicsas well as the textureand surfaceof the final product. The more alkaline noodleswere most attractiveinappearance,but on cookinghadsofter texturesandstickier surfacesthan lessalkalinenoodles.

References

I. 'CRCHandbookof ChemistryandPhysics'(R. C. WestandM. J. Astle,eds.),CRCPress,Florida(1981)62ndedn,p D-127.

2. Kervinen, R., Suortti,T., Olkku, J. and Linko, P. Lebensrn.-Wiss.Technol.18 (1985)52-59.3. King, H. G. C. Cherny Ind. 34 (1961) 1365-1366.4. Terada,M., Minami, J. andYamamoto,T. CerealChern.58 (1981) 101-105.5. Bean,M. M., Nimmo, C. C., Fullington,J. G., Keagy,P. M. andMecham,D. K. CerealChern.51 (1974)

427-433.6. Finot, P. A. In 'PlantProteinsfor HumanFood' (C. E. Bodwell andL. Petit, eds.),Nutrition Sciences

Vol. 2, Martinus Nijhoff, W. Junk,TheHague(1983)pp 440-453.7. Miskelly, D. M. and Moss,H. J. J. CerealSci. 3 (1985)379-387.8. Miskelly, D. M. J. Sci. Food. Agrlc. 35 (1984)463-471.9. 'Tablesfor the Quality SurveyoflmportedWheatCargoes',JapanWheatResearchAssociation,Tokyo,

Japan.10. Butcher,J. andStenvert,N. L. Milling 154(1972)27-29.II. AmericanAssociationof CerealChemists.'CerealLaboratoryMethods'.AACC,St Paul,MN (1978).12. Yamazaki,W. T. CerealChern.30 (1953)242-246.13. Moss, R. J. Sci. FoodAgrlc. 24 (1973) 1067-1076.14. Gurr, E. 'Methodsof Analytical HistologyandHistochemistry'.LeonardHill, London(1958)pp 79,91,

153.15. Maynald,E. C., Leach,H. W. andSchoch,T. J. Stiirke 20 (1968) 189-197.16. Moss,H. J. CerealChern.57 (1980) 195-197.17. Menger,A. Gertr. Mehl. Brot 34 (1980) 336-340.18. Dexter,J. E., Matsuo,R. R. andMorgan, B. C. J. Food Sci. 48 (1983) 1545-1551.