Chemistry Reference
In-Depth Information
9.1 INtrODUCtION
Qualitativeandquantitativedeterminationofthephysicochemicalandorganolepticproperties
ofsweetenerswillbedescribedhere.Somebasictestswillbeoutlined.Identiicationiseasyfor
puresugarsolutions,i.e.,solutionscontainingonlyonesugar.
9.2 MOLISCh teSt
Thisisageneraltestforthedeterminationofsugarsorcarbohydratesinunknownsolutions.
Phenola-naphtholisthesubstrateusedfortheMolischtestasareotherphenols,suchasthymol,
resorcinol,orphloroglucinol.Inthistest,furfuralorhydroxymethylfurfuralisformedbythereac-
tionofcarbohydrateswithsulfuricacidandisthencondensedwithphenoltogivethecharacteristic
color.
9.3 FeLIGION teSt
Thisisbasedonusingreducingsugarstoreduceanalkalinesolutionofcoppertartrateandform
ared-yellowcopperoxide.Aprecipitatewillnotbeformedinsolutionsthatdonothavereducing
sugars.ThisiscarriedoutaftertheMolischtest.
9.4 BarFOeD teSt
Thisisusedtodistinguishreducingsugarsbetweenmonosaccharidesanddisaccharidesandis
appliedtosolutionsthatarepositiveintheFeligiontest.TheBarfoedtestisusedtodetectlactose
ormaltoseindairyproducts.
9.5 reSOrKIN teSt
TheResorkintestisbasedonketosesproducingaredcolorinthepresenceofresorcinoland
hydrochloricacid.Itisusedtodistinguishketosesandaldosesand,mostspeciically,todetectfruc-
toseanddistinguishitfromthepresenceofothermonosaccharidessuchasglucose.
9.6 phYSICaL MethODS
Physicalmethodsareindirectmethodsandincluderefractometry,densitometry,andpolarim-
etryforsugardetermination.
9.6.1 Densitometry
Densitometryisadeterminationmethodfortheconcentrationofsugarsolutionsthatisnotas
exactasrefractometry.Densitometershaveaglasstubethatisthickeronitsbaseandfullofspheres
(dependingontheconcentrationrange)withathinnertubeontheupperpart,wherethereisascale
fordensitymeasurement.DensitometersmeasurethetotalsolidsofasolutionindegreesBaumé,
Twaddell, orQuevenne. Degrees Baumé isthe most used. Measurement iscarriedoutthrougha
directreadonthelevelofsolutionplacedonavolumetriccylinder.
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