Chemistry Reference
In-Depth Information
Final solubility at equilibrium
160
140
120
100
Usual range of supersaturation
Initial solubility of β-lactose
80
60
93.5°C
40
20
Initial solubility of α-lactose
0
0
20
40
60
80
100
120
Temperature (°C)
Figure 2.17
Solubility of
α
- and
β
-lactose as a function of temperature. (Adapted from Fox, P. F. and McSweeney,
P. L. H.,
Dairy Chemistry and Biochemistry
, Chapman & Hall, London, 1998.)
ingested lactose; it enters the large intestine, into which it draws water, causing diarrhea, and is
metabolizedbybacteriawiththeproductionofgasthatcausescrampsandlatulence.Inhumans,
thismayoccurateightto10yearsofage(Fox2009).
Lactoseisproducedindustriallyfromwhey,adairyby-product;byapplyingmembranetech-
nology,variousproteinproductsareseparated,whereaslactoseisrecoveredbycrystallizationor
drying (Fox 2009; Paterson 2009). Lactose can serve as a substrate for fermentation resulting in
theproductionofvarioususefulproductssuchasethanol,lactic,acetic,andpropionicacids.The
in
situ
fermentationoflactosebylacticacidbacteriatolacticacidiswidespreadintheproductionof
fermenteddairyproducts.
Duringdryingofmilkorwhey,lactosethathasnotbeenprecrystallizedformsanamorphous
glassthatisstableatlowmoisturecontent.Interestingly,crystallinelactosehasverylowhygroscop-
icityandisusedinicingsugarblends.However,incertainfoods,lactosecrystallizationisundesir-
able,suchasinsweetenedcondensedmilkoricecream.Owingtoitsrelativelylowsweetnessand
lowsolubility,theapplicationsoflactosearemorelimitedthanthoseofsucroseorglucose.The
solubilityoflactoseislessthanthatofmostothersugars,whichmaypresentproblemsinanumber
offoodscontaininglactose(Izydorczyk2005).Finally,likeallreducingsugars,lactosecanundergo
Maillard(nonenzymaticbrowning)reaction,resultingin(off-)lavorcompoundsandbrownpoly-
merproduction(Fox2009).
Maltose
:Maltoseisadisaccharideformedfromtwounitsofglucosejoinedwithanα-(1→4)
glycosidic bond (Figure 2.18). It rotates the plane-polarized light to the right and has a speciic
opticalrotationof
[
α
D
20
= +
136
°
.Maltoseisthemajorendproductoftheenzymaticdegradationof
CH
2
OH
CH
2
OH
O
O
H
H
H
OH
H
H
H
OH
OH
H
O
O
H
H
H
OH
H
OH
Figure 2.18
Structure of maltose.
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