guar gum properties

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J Soc.osm,. Ghm. 22 43-60 (1971) 1971Society f Cosmetichemistsf GreatBritain

Guar gum and its applicationsR. J. CHUDZIKOWSKI*

Presentedt theSymposium n "Gumsand Thickeners",organisedby the Society of CosmeticChemistsofGreat Britain, at Oxford, on 15th October1969.

Synopsis--The SOURCES and industrial PROCESSING of GUAR GUM are reviewed. Anaccount s given of its CHEMICAL reactions and the changes n PHYSICAL preparationswhich accompany hem. Somepitfalls in the utilization of guar gumsresulting mainly fromtheir high rate of ABSORPTION of water are discussed ogether with TECHNIQUES foravoiding such problems.INTRODUCTION

There seems o be a semanticambiguity about the very term "gums".Accordingo the originaldefinitionwhichmeant broadly"plant exudates",the term encompassedlsovarious esins, ubber latex, etc. The presentdefinition f "gums" s somewhat arrowerand morespecific.t comprisesall materials that can be dissolved r dispersedn water to form more orlessviscous olloidalsolutionsor dispersions.Whicheverdefinitionwe accept, t appears hat "gums"havebeenusedin industryand commerce ince he beginning f civilization.Accordingothe Bible, myrrh and frankincense ccompanied old at the Manger.Gumswere alsoused by the ancient Egyptians for embalming he dead and forglueing together strips of clothing for binding mummies. In differentapplication again gum arabic was for them a convenient adhesive formineralpigments n paint formulations. ikewise,gumswere usedas foodand for medicinal urposes y many civilizations, p to the presentday (1).Until recently,however, he useof gumswasrestricted o a relatively ow

*Rimreel Manufacturing Company Ltd., Ashford, Kent.43


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44 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS

numberof items,randomlyharvested,and of limited quality and propertyrange.Only the last decade,or so,has brought about revolutionarychanges.Some gum bearing plants have begun to be cultivated on a commercialscale. Many natural gums are now treated, and, by undergoingvariousphysicaland chemicalmodifications ave their quality improved,have therangeof their propertiesmmenselyncreased. inally, the creationof new,organicpolymershas yielded he whole classof new, syntheticgums.

Guar gum is one of the outstanding representativesof that newgenerationof plant gums. Its source s an annual pod-bearing,drought-resistant plant, called Guar, or cluster bean (CyamopsisetragonolobusrC. psoraloides), elonging o the family Leguminosae.t has beengrown orseveral housandyears in India and Pakistan as a vegetable,and a foragecrop. It is interesting o learn that someGuar seedshave even been foundin the recently excavatedPharaoh Zoser's omb in Sakkarah, nr. Cairo.

The guar plant is about 0.6 m high, and resembles oyabeanplant ingeneral appearance,and in its characteristicarrangementof pods alongthe vertical stem.The podsare 5-12.5 cm ongand containon he average5-6round, light brown seeds.The plant was brought to the U.S.A. at the beginningof this centuryand grown there in experimental stations in the semi-arid south west{South Texas and Arizona). It has been found fairly easy to cultivate,undemandingand well adapted to mechanicalplanting and harvesting. twas, however, only about 1940 that guar became a commercial eality.The war causedshortages n supply of locust bean gum, to which guargum is closely related, and the American paper industry began to lookfor possible eplacements.Guar gum was found to be a suitableone and,as a result, new plantations of guar bean began to spring up and in 1942General Mills Inc. introduced - experimentally - the first guar gum toAmerican ndustry (2).The successof that introduction and an increasing demand havenaturally attracted followers nd - amongothers in 1953anothermajormanufacturer Stein, Hall & Co. Inc.) entered the market (3). Now, guargum is big businessn the U.S.A. as may be seen rom Table I comparingproduction f more mportantwater solublegums n 1963 4).The more important brands in the U.S.A. are: Guartec,Arearex and"SuperCol" GeneralMills Inc.), "Jaguar" series Stein,Hall & Co. Inc.),

"Starguar" (Morningstar Paisley nc.), Penguar (S. B. Penick & Co.),T.I.C. Guar Gum {Tragacanth mporting Corp.), Guargum MeerCorpora-


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GUAR GUM AND ITS APPLICATIONS

Table I

Gum ArabicGum karayaLocust bean gumPsyllium seedGum tragacanthGuar gum

Productiont

21.010.08.03.01.626.0

Market value$ x 1065.25.12.71.07.27.8

45

tion) and severalothers.In Europe to the writer's knowledge there are the followingbrandsavailable: "Guaranate" series made by Socidtd Fran9aise des Colloidesand American brands, manufactured by their subsidiaries, .e. "Guartecand Supercol"of GeneralMills Inc. in the U.K. (Messrs. ragasolProductsLtd., Hooton, Wirral, Cheshire)and "Meypro-Guar" of Stein, Hall & Co.Inc., in Switzerland MeyhallChemicalAG - Kreuzlingen,Switzerland.)The general outline of the manufacturing procedure s as follows:After having been removed rom their pods the spherical,brownishseeds,

the size of a small pea, are passed apidly through a flame and thusloosened;hard seed hulls are then removed in a scouringor "pearling"operation.The decorticated, itreous ookingendosperms separated romits germ in a milling operationand the resulting"splits" are then groundto the requiredmeshsize.This is so called commercial guar flour" and it may be usedwithoutfurther processing,except for heat treatment to inactivate enzymescontained n occasionalragmentsof a seedgerm. Variousgradesare avail-able depending n colour white to greyish),meshsize,viscositypotential,

and rate of hydration.THE CHEMISTRY OF GUAR GUM

The chemical analysisof guar flour shows he following typical com-position: ToNitrogen 0.67 correspondingwith 3.5 - 4.0 proteinsPhosphorus 0.06Ash 1.07


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Water sol. polysaccharide 86.50Water insoluble fraction 7.75Alcohol sol. fraction{from24 h Soxhletextraction) 1.50The solvent xtractedraction onsists ainlyof a fatty matterwhilethe water nsolubleractioncontains roteins ndcrude ibres.The materialalsocontainsbetween10-13% moisture.The watersoluble olysaccharideractions composedapart romsome entosans,nd races f proteinaceousatter entirelyof approxi-mately 6.6%D-galactosenhydride,nd63.1/0 annosenhydride.he

absencef uronicaciddifferentiateshis polysacchariderom the greatmajority of plant gumsand mucilages.The compositionhus ound, dentifiest asa polymer f D-galactoseand D-mannose,.e. a galactomannan5).Thechemicaltructuref thisgalactomannanasbeenhe subject f agreat deal of study (6-8). Various methodshave been used. Chemical:acidhydrolysis ith subsequentdentificationf the componentsy theirosazones,r by paperchromatography, ethylation, eriodate xidation,and formationof tolyl sulphonyl-derivatives; iological: y meansofselectivenzyme ydrolysis; hysical: y studyof optical otation,nfra-redspectrography,tress-strain easurement,nd X-ray analysis f filmsofpure galactomannanand its acetate, etc.Theconclusionsrawn rom hose arioustudiesymany ndependentinvestigatorsre in substantial greement. he guar gum molecules alinear,or highlyanisodimensionalarbohydrateolymerwith a molecularweight n the orderof 220000 {9). t is composedasically f a straightchain f D-mannosenits, inked ogether y {1--4)glycosideinkages,andhaving napproximatelyvery lternatemannosesingle -galactoseunit, oined o it by an a (1-6) glycosideinkage Fig. 1).This polysaccharides representativef a groupof galactomannangums, btainablerommanyof theLeguminosaelants' eeds, hereheyserveas foodreserve. xamples: lfalfa, clover, enugreek nd, the bestknown,ocust ean carob.) lthough loselyelated hemically,hegumsdiffer somewhatn their structure.For instance, he chief differencebetweenguar,and locustbeangums s that the former s richer n D-galactosegroups1:2) than he atter 1:4). Thisaccountsmong thersorguargumbeingmore eadily olublen water,especiallyold.Also, s1-6glycosidiclinksare airlyeasily ydrolysedy acids, uargumbeing ichern galac-rose ashigher cidstabilityhan elatively oorer1:4) - i.e.more asily


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GUAR GUM AND ITS APPLICATIONS

HzOH

H OH

C.HOH

Figure 1.

47

"stripped" locust bean gum, which fairly rapidly loses ts viscosity nacidicmedia.There existsa galactomannan hich s evenricher n galactosethan guargum, and has correspondinglyifferentproperties.t is obtainedfrom seeds f Fenugreek lant (Trigonella oenumGraecum)10).Further processingf crudeguar flour consists f preparinga mucilage,which after autoclaving o destroypossibleenzymes s freed from theinsolublepart by centrifugation supercentrifuge,0 000 rev min-1). Fromsuchclarifiedmucilage, he galactomannans then precipitated n variousfractionsby the gradualaddition of ethyl alcohol.Those fractions are then filtered, dried, milled and blended to a desiredgrade o meet a wide variety of industrialprocess nd productneeds.The"natural" galactomannan rades,differ mainly in their purity, particlesize,dispersion roperties, ate of hydrationand viscositypotential.Theyare whitish powders,with bland taste, edible, but with relatively littlenutritional value. They meet the requirements f the U.S. Food and DrugAdministration G.R.A.S.) and on accountof that and their other beneficialproperties re usedextensivelyn the AmericanFood ndustry.Guar gum may be identifiedamongothersby its perfect solubility ncold water resulting n a viscoussol which gives a gel-like complex with

23Fehling,nd oraxolutions,nd xhibitspecificotationa) q-60 n0.6N NaOH.

Further possible rocessingf guar gum depends n chemicalmodifica-tions.Various reatmentsare nstrumental n developingunctionalcharac-teristics hat make this gum versatileand useful n a variety of industrial


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applications.he simplest hangesby varying he degree f polymerizationby controlledhydrolysiswhich is the means of controllingviscosity.Furthermore, the abundanceof hydroxyl groups n the galactomannanmolecule ends tself - like in cellulose to a variety of chemical eactions.They canbe easilyesterified,esultingn a varietyof nterestingompounds.Guar triacetate - for instance obtainedby reacting he galactomannanwith aceticanhydride n pyridine, s insolublen water, and can be castinto strong, lexible ilms,with properties omparable ith thoseof celluloseacetate.

Alkoxylationwith ethyleneor propyleneoxides s also easilycarriedout producing he correspondingthers. Carboxyalkyland cyanoalkylethers are another exampleof functional modifications, .g. o-carboxy-methyl derivative preparedby reacting galactomannanwith chloro-acetic acid - forms viscousaqueous olutions hat are stable to stronglyalkalinereagents 1).There are a host of chemical processesnvolving galactomannanssome f thempatented designedo endow he naturalgumswith a varietyof desired roperties including nionic nd cationic galactomannansreneutral and nonionic n character).

omplexingeactions reworthmentioning s hey ead o crossinkingof the moleculesesulting n a three dimensional etworkwhich manifestsitself n gel ormation.These eactions renot peculiar o galactomannans,beingcharacteristic f linear molecules aving an abundance f adjacenthydroxylgroups n cis positions. he complexingeactionof polyvinylalcoholwith borax is an example.Among others, copper salts form complexeswith galactomannans.Fehling's olution,or instance, oesnot reduce hosepolysaccharidesvenon prolongedboiling.An insoluble,gel-like complex s formed nstead.Salts of Ca, A1, and Cr have the same gel forming capacity at certainpH levels.Perhapshe mostcharacteristic,nd mportant, s the reactionnvolvingborate ons. Like in the caseof PVA borate ion co-ordinateswith 4 hy-droxyl groupsof two chain molecules,esulting n a di-diol complex.This reactionhas traditionallybeen representedy Fig. 2 (3). It is nowthought,however, hat hydrogenbondingprovidesa better explanationfor the forces nvolved n tiffs cross-linking ction. n accordance ith tiffs,the following s suggested s a more likely representation f the guarcross-linked olecule Fig. $). This reactionwill proceed venat extremelylow concentration f both galactomannan nd borate ons. The addition


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GUAR GUM AND ITS APPLICATIONS 49

Guar Binateon Guar Cross-inked Guar pH 8-0 ''

HCOH HOCH pH7.0 0 / 0 Hydrated

Guar ol Guar el(pH 7.0 ) (pH 8-0)

of as little as 0.05% borax (basedon solutionweight) at alkalinepH issufficient o fully gel a 0.25% galactomannan olution.The gelscan alsobe formedby adding boric acid, and then alkalis togivean alkalinepH - the optimum eingbetween .5-10.5.These elsmay

(Hydrogenbondingshown y ..,)Figure 3. Hydrogen bonded cross-linkedguar

have somewhat ifferentproperties epending n the gum gradeand con-centrationused. n general, hey are rubbery masseswhich exhibit coldflow properties, oalesceeadily after beingsubjectedo shear,and showno syneresis. hey remain essentially table for long periodsof time atalkaline H, butcanbe,however,asilyeconvertedo thesol ormby simplyaddingenoughacid to adjust he pH to less han pH7. This reaction scompletely eversible, nd the sol-gd-sol equence ay be repeatedasoften as desired.

Another nteresting henomenonccurswhen the gum, in powderform, is introduced into an alkaline borated solution. Under these condi-tions, he gum will disperseasily,but will neitherhydrate,nor developviscosity. his inhibitingactioncan be overcome y simply owering he


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pH to 7, or below.The gum will then hydrate and developviscosityn theusual manner.This phenomenon ay be utilisedasa way of dispersinguarcontainingproducts, hat tend to lump, especially ith not very efficientequipment.The powder s initially slur led into an alkalineboratedsolution,which sthen neutralized o promotehydration (3).An interestinguse of someof the properties f boratedgalactomannansis made n a patent (11) for hair straightening omposition ith sulphites.The rationaleof this applications that suchboratedgumshave a verylow initial rate of hydration n acidicmedia hus enabling he product inpowder orm - to be easilydispersedn water. The resultingsolutionwetsthe hair easilyand conveniently nd after a while develops igh viscosity(of the orderof $ 500 cP) which,aidedby combing,manageso keep nthe desiredshape he sulphitesoftenedhair.Guar gum gradesare also availablepossessingellingproperties asedon a principle entirely different from that of the borax/galactomannansystem.They eitherutilize an oxidising atalyst o activate he complexingmechanismn a two-stepprocedure,or are "one step" and entirely selfcomplexingypes. The latter form solson dispersion, nd then developinto firm, water-tight gels 2, 3).

PHYSICAL PROPERTIES OF GUAR SOLSGalactomannans re insoluble n hydrocarbons, ats, alcohols,esters,ketones in fact with a very few exceptions e.g. formamide) n organicsolvents n general. The only important solvent for galactomannansswater, for which - on accountof the structureof their molecule theyhave tremendous ffinity - for water in its liquid state - that is. Wate in

the vapour phasemerely changes he moisture equilibrium. There is nohygroscopicity.When dispersedn water, hot or cold,galactomannansydrate rapidlyto form colloidalsolutionsof unusuallyhigh viscositycharacteristicsvenat very low concentrations.Table II indicating concentrations f various hydrocolloids equiredto producean apparent viscosityof 800 cP at 20Cshows hat a brandof guar gum is - in that respect a runner-up o Carbopol.What is evenmore remarkable,guar gum attains nearly its full viscositypotential n coldwater, while othergums includinghe related ocustbeangalactomannan)equiresometimes rolonged cooking".


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GUAR GUM AND ITS APPLICATIONS 51Table II.

GumTragacanth USPSodium alginate (med. visc.)Jaguar brand of guar gumMethyl cellulose (1 $00 cP)Methyl cellulose (4 000 cP)Sodium carboxymethyl cellulose (reed. visc.)Sodium carboxymethyl cellulose (high visc.)Carbopol934

o (w/v) for 800 cP2.751.150.2-0.3 (2SC)1.71.351.90.70.17

5O

4O

30

20

10

0

_J

,' Hydrofed 25C Hydrofed 85CMeasurernenfs o1' 25C

sols

2 .=---

.--

Figure 4. Viscositypotentialof some common ater solublegums.

Coldprocessing,owever, ffectshe rate of hydrationwhich s greatlyacceleratedy increasinghe temperature. or example,with a particulargradea degree f full viscosity evelopmentequiring h at R.T. is accom-plishedn about10 min at the optimal emperature f 80C.Viscositys often taken as a common enominator nd performanceindex n comparing ifferentgrades f guar gum.Thereare five variablesthat determine he pattern of viscositydevelopment nd the behaviourof a given guar gum grade n an aqueous ystem.viz: concentration,dispersion,emperature,pH, and presence f foreign substances113).Understandingheir implicationss of greathelp n formulatingwith guargum or processingt.


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As can be seen rom Fig. 5, the incrementalncreasesn the gumconcentrationesult n almostexponentialncreasesn viscosity p to aconcentrationf about1.5%. At concentrationsigher han about3%(dependingn a grade),guargums orm elly4ikepasteswhich,however,are not true structural gels.

.[

I00,000

1,000

I00

Concen'l'rafion, %

Figure . Variation of viscositywith concentration.

For comparing iscosities f guar gumsa "standard"concentration f1.0% (w/v) is usedas a rule. Quantitativemeasurementsre best carriedoutwitha torsioniscometer(e.g.rookieldRVF,Syncro-Lectricypewitha No.3 spindlet 20revmin- ), althoughorqualitative omparisonsthermethodsike, for nstance,Ford"cup,maybe employed.t is essentialostate he method f measurementhilequoting iscosity.Guar gum solution iscosities in common ith mostotherhydro-colloids arestrongly ependentn shear ate,andcanbe moreproperlydescribeds"apparentiscosities".n short, uargumsols re hixotropichaving,however, relatively ow yield value.


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The prerequisite or the sol formation is an efficientdispersion f thegum particles n water. As in most other hydrocolloids, adly dispersedlumps tend to become"encapsulated"with a hydrated layer preventingfurther water penetration.The tremendous ffinity for water possessedyguar gum is utilized industrially. t is used as a "water sealer" n oil welldrilling or in protectingexplosivesrom getting wet. In the latter case,water leaking through a chancepuncture n a cartridge s taken up bythe gum o form a thick solwhichcompletely locks he puncture o preventfurther water entry.To effectsolution, he gum must be thoroughlydispersed y sprinklingit ontowater, ascoldaspracticable,with vigorous tirring.On an industrialscalesifting through a screenor grid from the edgeof a shaker ray or theuse of an eductor are recommended.

Other expedients o promotesolution ncludepremixing he gum withother powderedsubstances, .g. sugar, or dispersing t in pre-retardants(e.g. alcohol,glycerine,glycols,acetone,etc.) before ts addition to water.Finally, the gum may be dissolvedmore readily in certain salt solutionsthan in water, e.g. in solutions f sodiumof calciumchloride.The effect of temperatureon the rate of hydration and the time toattain the full viscositypotential has already been discussed. s all solu-tions, he guar solschange heir viscositywith temperature Fig. 6).

60

5O

40

3O

20

On

S01s reparednd ! 'eringfullyhydrated25* eforeemperaturehencje- I

I_ I

II

-o c Io 2o 3o 40 50 o 7o Bo 9oViscositymeasurementemperature, c

Figure 6. Measurementof temperature effect on fully hydrated sol.


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Compared,however,with many other gums' solutions hey exhibitexcellentretention of viscosityat high temperatures.They can also bemaintainedat high temperaturesor long periodsof time with practicallyno effecton their ultimate viscositymeasured t room temperature.One of the characteristics f guar gum solutions s their stability overvirtually the entire usablepH range. This property is attributed to thenonioniccharacter of galactomannans.With the exceptionof values over10.5 the viscositypotential is not greatly affectedby pH. Its peak isbetweenpH valuesof 7-9, and the practicalstabilityrange rompH 4-10.5.In the presence f strongalkalis the viscosity alls fairly sharply,althoughthere is a suggestionhat this may be due to destructionof the proteinswhich form a complexwith the carbohydratepolymer (1).It is possibleo prepare airly high viscosityguar gum solsat high pHvaluesby first effecting heir hydration at a neutral pH for 30-60 minand then adjusting the pH with alkalis.

3.0

c 2.?u 2.4

ou

2 $ 4 ' 6 7 8 9 I0 I1pH

Figure 7. Viscosity of a guar gum as a function of pH value.

Moreaffectedby the pH is the rate of hydrationwhichagain s highestbetween he pH valuesof 6-9 and the lowestat approximately .5.This knowledges useful n preparingsolutionsof "difficult" formula-tionswhichcanbe easilydispersedn coldwater at pH 3.5, and the solutionobtainedspeedily,with the desired iscosity released" y adjusting hepH to 8, and - if necessary heating he solution o 80C.Anotherconsequencef the nonionic haracterof guar gums s the factthat their solutions re uncommonlyesistant o electrolytes. hey arecompletely naffected y hard water, and will tolerate arge quantitiesof


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electrolytes hat will "salt out" most of the other gums. t must be bornein mind, however, that there is no singlerule as there exist severalmannersof interactionbetween he gum and the dissolved ubstance.Complexingwith boron,aluminium,copper,chromiumand other salts have alreadybeendiscussed.lthoughnonionicn nature, he gum particlesmay acquirean ionic chargeby absorbing ther ons from solution.This in turn mayaffect their properties .g. rate of hydration and ultimate viscosity. t hasalready beenmentioned hat sodiumand calciumchloridesolutionspeedup guar gum hydration without affectingviscosity.Sodiumbenzoate,however,not only accelerateshe rate of hydration,but alsoconsiderablyincreases iscosityof the resultingsolution. On the other hand, salts likesodium sulphate nhibit hydration of the gum, depress iscosity, and inlarge quantitiesmay cause ts precipitation.The explanationof the latter phenomenon eems o lie in the fact thatthe gum,andthe dissolvedubstance,re competingor water. The strongerthe affinityof the salt for water as n salts orminghydrates the strongerthe inhibiting effect. This also explains ncompatibilityof the gum withwater misciblesolvents ike alcohol,acetoneor glycerine, hat rapidlydeprive he gum of water causing he former'sprecipitation.The under-standingof these acts also suppliesa rationale for empiricallyevolvedmethodsof dispersinghe gum using dry mixing techniqueswith, say,sugar, or wetting out with alcohol,acetoneor glycerine.Apart frommechanicallyseparating he particles, when in contact with water, theinhibitors preferentially ake it up, slowinghydration of the gum andallowing t to becomehoroughlywetted, and dispersed. his effect s thennegatedby dilutionuponwhich the gum'shydrationproceeds ormally(13).Another important property of guar gum explaininga great deal ofits behaviour s its hydrogenbondingactivity. This is generallyattributedto the presence nd behaviourof numerous ydroxyl groups.The basicstraight chain structureof the galactomannanmolecule,along with theregularityof the singlemembered alactose ranches,esult n a productthat exhibitsan unusual ffecton otherhydratedcolloidal ystemshroughhydrogen onding. ecause uargumwill hydrogen ond o both hydra-ted mineral and organic surfaces, here are few systemswhich will beunaffectedby its action. The addition of even extremelysmall quantitiesof guargumcanmarkedlyalter the electrokinetic roperties f the systemtreated. As a broadrule, it can be saidthat guar gum in appreciable uantities


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will act as dispersant or organicsystems, specially hosewith functionalhydroxyl groups,and as a coagulant or inorganicones, n particular forthosewith "clay" characteristics. his property togetherwith its relative-ly low yield value - means hat cautionmust be exercisedwhen usingguargum solution or pigmentsuspension.here are, however,availableanionicgradesof guar, well suited or that purpose 15).In extremelysmallquantitiesguar gum tends to act as a flocculant orboth inorganic and organic systems,and this property has beenutilizedin some ndustries e.g.mining)whereguargum s employed s a flocculant,settlingagent, and filtration aid.

The hydrogen ondingphenomena xplain,amongothers, he excellentcompatibilityof guar gum solutionswith other hydrocolloids,ike agar,alginates, um arabic,British gum, ocustbeangum, carrageenan, ellulosederivatives,gums karaya and tragacanth,pectin, starches,gelatin, andother water solubleproteins.It is not only a questionof compatibility there is evidence hat inmany instances here is a distinctly synergisticaction. Co-solutions fseveralof thosehydrocolloidse.g.starches)with guar, exhibit muchhigherviscosities,and stabilities than either ingredient alone. Combination ofguar with agar or carrageen romotes ormationof a structuralgel.Hydrogen bonding also explains why guar gum is such an excellentbeateradditive n the processingf paperpulp. A smallamountof guargumsolutionaddedbreaksup agglomerated ellulose ulp fibres and dispersesthem uniformly n the pulp slurry.Solutionsof most guar gum gradescan be dried to form flexible filmswhich resistmost organicsolvents,but which readily redissolve n wateror aqueoussolutions.Textile sizings, or instance,use such temporaryfilms for protectionof fibresduring the weavingprocess. omederivativesproducewater resistant ilms, guar triacetate being the most prominentexample.Guar solutions ave slightly acidicreaction pH 5.5-6.1), and if sterileare perfectly stable n storage.They are, however,as are the other naturalhydrocolloids, ubject to microbiological eterioration,which results n alossof viscosityas the first tangiblemanifestationand in a loweringof thepH value.If unpreserved, uar gum solutionshouldbe usedwithin 24 h. Shouldits usebe delayedpreservativesmust be employed.

In the food ndustry sodiumbenzoateand sorbicand benzoicacidsaremost commonlyusedfor that purpose.Other industriesmay successfully


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use formaldehyde, substituted phenols, lauryl sarcosinate,and phenylruercurie acetate.

USES OF GUAR GUMTable I shows that guar gum is used in massive proportions inindustry. ndeed,due to its uniquecombination f propertiest hasprovedto be a valuableaid in a multitude of industrial applications,as diverseasalreadymentioned,mining and food, paper and textile.In the paper ndustry t is further used- apart from as a dispersant ndsuspending gent - also for sizingand coating. n the textile industry talsoserves s a pigmentdispersing id, and aboveall as a thickeningagentfor colourprinting pastes or which use t is unsurpassed.The ceramic ndustry also usessizeablequantities of guar gum as abinder, thickenerand fixing agent for enamels,porcelain,etc.In the food industry it is widely used n salad dressings,ce creams,lollipopsand sherbets, n bakery productsand confections,meats andsausages, heese preads, nd many other applications.In the pharmaceuticalndustry,dry guar gum is usedas a disintegrantand n solutionas a binder in compressedablets manufacture 14). It isalsoused n liquid dieteticpreparations s a low calorie hickener o improvetheir mouth feel, body and pour characteristics.On accountof its hydro-philic propertyand the ability to form bulky, jelly-like masses,t is usedin appetite depressantss a bulking agent n laxatives, and in gastriculcer

treatment.It has also suchmiscellaneous sesas a thickener for battery electro-lytes, printing nks, and as an ingredient n paints,adhesives nd polishes.

GUAR GUM IN THE COSMETIC NDUSTRYIt would appear that a raw material endowedwith sucha variety ofusefulproperties, formidable iscosity uilderwith an unusual,excellentcold solubility, a solventresistant ilm former, protectivecolloid,with awide rangeof compatibilities, ntroubledby pH changes nd the presenceof salts, stable,nontoxic, afeand cheap,wouldbe immediately cceptedby the cosmetic ndustry. This is, however,not the case.The industrytends o be shy of materialsnot createdspecifically or its use, and slow otranslate to its benefit the experienceof other industries.


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This may alsobe true because, lthoughmost guar gum manufacturersrecommend ts use in cosmeticsn general, concrete nformation is scarceas are patentsand available ormulations.Guar gum is usedon a sizeable cale n the manufactureof tooth pasteto which t imparts slip, so that the pastecan be extruded rom the tubewithout applying excessive ressure.Similarly it is used n someshavingcreams,where t stabilizes he system, mparts slip in extrusionand on theskin,while shaving,and improves acial skin after feel (16).It lends tself perfectly o be used n emulsified ystems: reamsandlotions as a protectivecolloid, ncreasingemulsionstability, preventingsyneresis, ater loss,and phaseseparation.It alsopreventsdegradation f emulsiondue to freeze-thaw onditionswhich cause he water phase o condense ut of the system.For instance,used in an ordinary TriethanolamineStearate type lotion it gives it astableviscosity,mprovedspreadability nd mparts o it an agreeable fterfeel associated ith best quinceseed ormulated otions.In aerosols ispensingqueousiquid preparations s a sprayor mistit is said to reducemigrationof "fog" (16).Guar gum solutions re compatible nd mix well with most detergentsystemsshampoos,leansers,tc.) giving hem "body" and abolishing rminimizing their harsh after feel. Excellent hair colourantswere alsoprepared singguar gumsolution s thickener.Although not an emulsifier owing to its ready compatibility guargum solutions an be used n conjunctionwith other gumsendowedwithemulsifying roperties.An excellent,stable emulsionwas, for instance,preparedn the cold adding30-40% mineral oil into a 10% solutionofpolyvinylalcohol 80% hydrolysisow molecularweight) under vigorousstirringand then adding3% guar gum solutionand mixing to uniformity.When mineral oil was replacedby ShellsolT the resultingemulsionwasfilm forming.Self-emulsifying radesof guar gum are also available.Dry face maskmixeswere easilyand conveniently reparedusingguar gum plus additiveswhich in such systemmay even be heat- and moisture-sensitive.n use,the mixesneed only to be stirred nto a sufficiency f cold or tepid water(half a cupful) o produce rich creamypaste.It is hoped that these few exampleswill stimulate the interest ofcosmetic ormulators,and the content of this paper will help them insolving,successfully,he ensuing roblems. (Received:8thAugust1969)


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GUAR GUM AND ITS APPLICATIONS 59REFERENCES

(1) Smith, F. and Montgomery, R. Chemistryof plant gumsand mucilages 1959). (ReinholdPublishing Corp., New York).(2) "Guartec" (1963). (General Mills Inc.).(3) "Jaguar", (1962). (Stein, Hall & Co. Inc.).(4) Kirk and Othmer. "Gums, Natural" by M. Gliksman. Encyclopaediaof ChemicalTechnology, 0 (1966).(5) I-Ieyne, Eileen and Whistler, Roy L. J. Am. Chem. Soc. 70 2249 {1948).(6) Ahmed, Z. F. and Whistler, R. L. J. Am. Chem. Soc. ?9.2524 {1950).(7) Swanson, J. W. J. Am. Chem. Soc. 71 1510 {1945).(8) Rafique, C. M. and Smith, F. J. J. Am. Chem. Soc. ?9.,4684 (1950).{9) Moer, G. Jr. and Meer, W. A. Am. Perturner 77 49 {4, 1962).(10) Natural Plant Hydrocolloids.Roy L. Whistler. "Guar Gum, Locust Bean Gum andOthers" {Advancesn Chemistry eriet11. Am. Chem.Soc.) 1954)(11) Brit. Pat 1 076 420.(12) Gerding, P. W. and Sperandio, G. J. J. Am. Pharm. Assoc.Pract. Ed. t5 856 {1954)(13) Carlson, W. A., Ziegenfuss,E. M. and Overton, J. D. Compatability and manipulationof guar gum. Food Technol.16 50 (10, 1962).(14) Eherton, L. E. Platz, P. E. and Cosgrove,F. P. Drug Standards.9.8 No. 2, 42-47(19SS).(15) $chimmel Brief No. 401. (September, 1968).(16) Bulletin 1 GF-5 Supercol Guar Gum - Cosmeticand Pharmaceutical Uses. (GeneralMills Inc.).

DISCUSSION

MR. C. A. WATSON: n reply to the statement that guar is used in several leadingdentifrices in the U.S.A. I wish to state that we have not succeeded n making satis-factory toothpastes becauseof its incompatibility with glycerine, neither have wefound the Jaguar products fully satisfactory. I am not aware of any major U.S.A.toothpaste brand which relies on guar gum thickener.THE LECTURER: do not know which companies are concerned as I have that

information from the guar gum manufacturers' handout. They just state categoricallythat a few leading American companies use guar gum as a hydrocolloid in theirtoothpastes, and that has struck me as being feasible.You probably know better but, judging from its properties, guar gum wouldseem very useful becauseof its relatively high yield value, quick shear recovery andgenerally good compatibility. I have not tried it in toothpaste systems. However, Ihave tried guar gum in various emulsifiedsystems creams and the like - and in myexperience t has proved quite compatible with all polyols used in cosmeticsup to alevel of approx. 5%.

MR. D. N. MXDDOX:Natural gums such as tragacanth are often highly contamina-ted with bacteria and as a result products containing them are difficult to preserve.Is guar gum normally contaminated and, if so, can you give some dea of the bacterialcount?

THE LECTURER: t should not be contaminated in this way, because one of theprocesseswhich the natural guar gum undergoes s autoclaving. This expedient isdirected not so much against the bacteria, as against the enzymes which could have


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crept into the flour from the seeds or rather their germs.The germs contain enzymeswhich tend to depolymerise the galactomannan; to get rid of them, the standardprocedure s to autoclave the bulk, and that - at the same time - probably takes careof the bacteria as well.

I wish to emphasise hat guar gum is widely used in the food industry where themicrobiologicalconsiderationsare certainly important. It is easy to preserve, beingcompatible with sodium benzoate, which incidentally has an interesting property ofincreasing its viscosity, and with benzoic and sorbic acids, the preservatives mostfrequently used in the food industry.MR. G. A. GREINER:Could you clarify that the "viscosity potential" figures inpages 50 and 51 are for pure guar gum or are there additives, such as borax in theproduct cited?TF. LECTURER:This concernsnatural guar gum. The order of viscosities averages5 000 cP, for a 1% solution.DR. N. A. R. LERoux: Would you like to comment further about the synergistic

effect of guar gum with other hydrocolloids?T}m LEcx'mE: I have no experience of that.MR. ID. M. BUSFELD:t seems o be widely assumed hat a lot of guar formulationscontain borax. I would like to discount this belief because, n fact, very few guarformulations need to contain borax to achieve the viscosity potential.In the literature it has been reported that perhaps the structure of guar gum is

not as simple as you put it in the paper, and one of the common beliefs is that thestructure consistsof short chains of D-galactose units randomly positionedalong theD-mannose chain, rather than single D-galactose units positioned at regular intervalson every other D-mannose molecule. This possibly may account for some of therheological effects in that if the chains are longer than one molecule units there willbe some entanglement of the branches in the solution. Coupled with the hydrogenbonding effect this would give two reasons or viscosity,and may possibly account forthe pseudothixotropic effect. Would you care to comment?T LF_c,ut.R: You are perfectly right. Both Smith et al (1), and Heyneetal (5)comment on that. It must be realised that the formula quoted is an idealised one,

and has been arrived at by the way of quantitative analysis which gives about 6%of galacloseand 63% of mannose;consequently t has been assumed hat they are inthe formula in the proportion of roughly 1:2. This has led to an idealised picture butall investigators agree that this is not as simple as that. First of all, the proportionsnotwithstanding, the distribution of side chains may vary according to the naturalprocess(sccurring n the forming of the galactomannan, nd further changeswhichmay occur in processing.Quite a few authors also postulate the ramification of the chains. The existenceofshort branched chains of galaclose rather than units on the mannose chain is said toexplain quite a few anomalies (1, 5).

guar gum properties

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