Chemistry and Functional Properties of Carbohydrates and Sugars (Monosaccharides, Disaccharides, and Polysaccharides) - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 37

time—thesettingismorerapidatlowerpHvalues.Saltstendtodelaysetting,andsomesuchas
disodiumphosphateareregularlyaddedto“slow-set”pectins(Meyer1987).
2.5.2.3 Crude Fibers
Theterm“crudeibers”isusedtodeinethesumofallthoseorganiccomponentsofplantcell
membranes and supporting structures that, during chemical analysis of plant foodstuffs, remain
afterremovalofcrudeprotein,crudefat,andnitrogen-freeextractives.Thus,theibersaremainly
composedofcellulose,hemicellulose,andsomeofthematerialsthatencrustthecellwallssuchas
pectinsubstancesandlignins.Theibersconstitutethenondigestiblecarbohydratefoodingredients.
Thedeterminationofibersisdificultanddependsonthemethodused.Themethodsgener-
ally include removal of crude fat by ether extraction while crude protein is dissolved by hydro-
lyzingwithdiluteacid.Crudeibervaluesforagivenfoodshowthesamevariationwithseveral
factorssuchasclimate,soilconditions,anddegreeofmaturity,asdoothervalues(BeMillerand
Whistler1996).
Interestincrudeiberdeterminationscenterseitherinthedetectionofadulterationorfromthe
nutritionalstandpointinthebulkinessofthediet.Itisknownthatthecompoundsincrudeiber
makeupmostofthebulkorresidueofthedietandarenothydrolyzedbythedigestiveluids,and
thustheyarediscarded.Nevertheless,ithasbeenshownthatibersserveaveryrealfunctioninthe
dietastheyremainlongenoughinthestomach,coveringthesenseofhunger,whiletheyassistinthe
removalofotherwasteproductsfromthebody.Theiractionisimportantbecausesomeoftheibers
absorblargeamountsofwater,whichcontributestothecureofhyperglycemiaandotherdiseases.
2.5.2.4 Gelling Agents: Plant Gums and Seaweed Extract
Plantgumsandseaweedextractscontainsubstancesthatbelongincarbohydratecategoryand
havemanyapplicationsinfood;forexample,theyactasgellingagents,adhesives,orthickeners.
Theterm“gum”wasoriginallyusedforgummyandstickyplantsecretions,whilelateritwasused
todescribethecharacteristicofbeinginsolubleinwaterproductsor/andwater-solublesubstances.
Nowadays, gum is used for water-soluble thickening and gelling agents, while those insoluble in
water substances are classiied as resins. Various plant gums (guar gum, carrageenan, alginate,
agar)areusedinfoodsasgellingagentsorstabilizers.
Gumsarepolymeringredientsthat,inasolutionorwhendispersedinwater,cangiveathicken-
ingorgellingeffect.Asthesesubstancesareofcolloidalnature,theycanstillbereferredashydro-
colloids.Mostgumsthatindapplicationinfoodsarepolysaccharides.
Seed gums :Thiscategoryincludesguarorguarlourandcarobseedlour.Boththesegumscon-
tainmainlygalactomannans;guarlourcontentingalactomannansis80%-85%,andcaroblour
contentis75%-80%,butitcontainsgalactomannanswithfewerbranches.Theyaresubstancesthat
arestabletoheat,whiletheygetreadilyhydratedformingviscoussolution.
The guar gum can be easily dispersed in cold water compared with carob seed lour, which
needswarmwater.Galactomannansarecapableofforminghighlyviscoussolutionsatrelatively
lowconcentrationsandcaninteractwithmanypolysaccharides,improvingtheirfunctionality,thus
havingmanyapplicationsinfoods.
Plant exudates :Theyaregummysubstancesderivedfromsecretionsoftrees(acacia,cherry,
plum), which, on contact with air, get dried in chambers with gummy texture. The most famous
gumsofthisclassarearabicgum,tragacanthgum,andkarayagum.Thesegumsareheteropolysac-
charidemixturescontainingd-glucuronicord-galacturonicacidandthreeormoremonosaccharides.
Arabicgum,whichhasmanybranchesinitsmolecule,presentshighersolubilityregardlessofthefact
thatithashighermolecularweight.Onthecontrary,karayagumislesswatersoluble(Izydorczyketal.
2005).