Quality Control of Sweeteners: Production, Handling, and Storage - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 258

9.6.2 refractometry

Lightrefractionisthechangeindirectionwhenaircomesintowaterandisexpressedbythe
ratio(sina/sinb)ofanglesaandbandiscalledtherefractionindex.
Ifasugarsolutionreplaceswater,thentherefractiveindexdependsontheconcentrationandtem-
peratureofthesolution.Theconcentrationofthesolutioncanbecalculatedfromtherefractiveindex.
Refractometersmeasuretherefractiveindexandtheconcentrationofsolublesolidsinsolutions.
Therearetablescorrelatingtherefractiveindex,saccharose(inpercent),Brix,degreesBaumé,etc.
Saccharose solutions differ in the refractive index from the dextrose or fructose solutions of
thesameconcentration;hence,therearecoeficientsofconversionofsaccharoseintodextroseand
fructoseasdescribedbelow:

1. Saccharose(%)×1.020=dextrose(%).

2. Saccharose(%)×1.022=fructose(%).

Refractometers are based on the principle of increase in refractive index with an increase in
density.Therearetwodetectionsystems:(1)therelection(digital)systemand(2)thetransparent
system(mobileandAbberefractometers).

9.6.3 Brix (%)

Brix (%) measures the percentage of soluble solids in a water solution. This includes sugars,
salts,proteins,andacids.

9.6.4 polarimetry

Sugarsolutionsareopticallyactive,i.e.,theyturnthepolarizedlightlevel.Thisiscalledthe
speciicrotationalability(SRA)andisdirectlyproportionaltotheconcentrationandtypeofsugar,
ascalculatedinEquation9.1:

100 a

L C

*

α 20 SRA = [ ] = , (9.1)

D

*

where
+[ α 20 =SRA10%sugarsolutionat20°C
a =turn
L =lengthofpolarimetertube(incentimeters)
C =solutionconcentration(ingramsper10ml)

Opticalbalanceisachievedthrough

1. Addingsomedropsofammoniatothesolution

2. Heatingthesolution

3. Applyingultrasoundtothesolution

CalculatingtheturnofthepolarizedlightαandtakingthevalueofSRAfromatable,wecan
calculatetheconcentrationinthesolutionfromEquation9.2:

100 *

*[ ]

a

C = gr/ 100 ml .

(9.2)

20

L a D