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International Starch Institute
Science Park Aarhus, Denmark
ISI 06-1e Determination of Dry Matter in Syrup by Refractive Index

1. Scope The method is applicable to glucose, maltose and fructose syrup


JK 03. Feb. 1967
Rev. LT 24 Nov. 1997
2. Principle The refractive index of sample is transformed to dry matter by a polynominal function or table.


3. Apparatus 3.1 Refractometer, thermostated


4. Procedure Adjust temperature of refractometer (3.1) to 45 oC. Degree Celcius = t
Adjust sample temperature to that chosen for the refractometer.
Place a few drops of sample on fixed prism and close instrument Work fast
Read the refractive index (nD45) to nearest 0.0002 unit.


Clean prisms immediately after.
5. Calculation Correct index to index at 45 oC (nD45) if not measured at 45 oC temperature and calculate dry matter (DM) in percent of sample (average results of two samples with no decimal):

nD45 = 0.000065* nD * (45-t) * nD3

DM % = a * nD452 + b * nD45 + c

Within the indicated range of dry matter the results is in agreement with table values for DM% +/- 0.3

...or use tables

Temperature correction only valid within a narrow range.

Revision ongoing !



Acid converted

28 DE

Table 1a

42 DE

Table 1b

55 DE

Table 1c

Dual converted

32 DE

Table 2a

63 DE

Table 2b

70 DE

Table 2c

95 DE

Table 2d

High maltose

42 DE

Table 3a

50 DE

Table 3b

Fructose syrup

42 %

Table 4a

55 %

Table 4b

90 %

Table 4c

6. Reference International Standard: ISO 1743

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Keywords: laboratory,method,determination,dry matter,substance,starch,glucose,maltose,dextrose,fructose,syrup,refraction,refractive index