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moredextrose(glucose)andarethereforesweeterandhavegreaterhumectantpropertiesthanlow
DEsyrups(GamanandSherrington1990;PenieldandCampbell1990;BlanchardandKatz1995;
Belitzetal.2009).
2.5.1.2 Cellulose
Cellulose is the most abundant naturally occurring polysaccharide on earth. It is the major
structuralpolysaccharideinthecellwallsofhigherplants,whereitusuallyoccurstogetherwith
hemicelluloses,pectin,andlignin(Belitzetal.2009).Itisalsothemajorcomponentofcottonboll
(100%),lax(80%),jute(60%to70%),andwood(40%to50%).Cellulosecanbefoundinthecell
walls of green algae and membranes of fungi.
Acetobacter xylinum
and related species can
syn-
thesizecellulose.Cellulosecanalsobeobtainedfrommanyagricultural
by-productssuchasrye,
barley,wheat,oatstraw,cornstalks,andsugarcane(Izydorczyketal.2005).
Beingpresentinfruits,vegetables,andotherfoods,celluloseisofgreatinterestbecauseitcon-
tributestobulkinthediet.Itisnotanutritioussubstancesinceitcannotbeutilizedbythehuman
body,whichlacksthenecessaryenzymestodigestit.However,wheningested,cellulosedoescon-
tributetotheeliminationprocessbecauseofthebulk(Lee1975).
Cellulose is a polymer composed of glucose units joined by β-d-(1→4)-glucosidic linkages
(Figure 2.24). During its hydrolytic cleavage, the disaccharide of cellobiose is being formed.
Cellobioseisadisaccharideoftwoglycoseunits,whichdiffersfrommaltoseintheconiguration
ofthe1-carbon.
TheDPdependsonitsnatureandcanrangefrom1000to14,000(withcorrespondingmolecu-
larweightsof162to2268kDa),whileitsmeanmolecularweightcanbedeterminedbyviscosity
measurement, ultracentrifugation, and end group analysis. Most determinations give ranges of
values,indicatingthatthesamplesarecomposedofmoleculesofdifferentmolecularsize(Meyer
1987).
Becauseofitshighmolecularweightandcrystallinestructure,celluloseisinsolubleinwater.
Also,itsswellingpowerorabilitytoabsorbwater,whichdependspartlyonthecellulosesource,is
poorornegligible(Belitzetal.2009).
Pure cellulose is a white, amorphous mass and insoluble in water, ethanol, ether, cold dilute
alkali,anddiluteacids.Itisdissolvedintheammoniumsolutionofcopperoxide(ARSchweitzer).
Theparallelarrangementofitslongmoleculesintoibersexplainsitsmechanicalproperties.
ThechemicalstructureofcellulosehasbeenclariiedbyX-raystudies.Therearetwotypesof
cellulose:1)iber,whichisderivedfromtheparallelarrangementoflongmoleculesandistherigid
partofplanttissues,and2)amorphouscellulose,whichconsistsofdisorganizedpartsandisthe
lexiblepartofplanttissues.
Apuriiedcellulosepowderisavailableasafoodingredient.Thepowderedcelluloseusedin
foodshasnegligiblelavor,color,andmicrobialcontamination.Powderedcelluloseismostoften
addedtobreadtoprovidenoncaloricbulk.Reduced-caloriebakedgoodsmadewithpowderedcel-
lulosenotonlyhaveanincreasedcontentofdietaryiberbutarealsopreservedmoistandstayfresh
longer.
CH
2
OH
CH
2
OH
CH
2
OH
H
C
O
C
H
O
H
O
C
H
H
H
C
C
C
C
O
OH
H
O
C
C
H
O
H
H
OH
OH
C
C
C
C
C
C
H
H
H
OH
H
OH
H
OH
Figure 2.24
Structure of cellulose.
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