ISI 44-1e Determination of Whiteness by Reflection


1. Scope The method is applicable to starch

 

 LT 12. Dec. 1966
2. Principle Light reflected from a sample relative to the reflection from magnesium oxide is measured.

 
3. Apparatus 3.1 Photometer (Whiteness meter / Reflection meter)  KETT C100
4. Reagents 4.1 Magnesium oxide standard
5. Procedure Fill starch sample in vial identical to the one used for (4.1) magnesium oxide. Follow instructions for the instrument used.

 

 Measure reflection from starch sample = A

Measure reflection of 4.1 magnesium oxide standard = B
6. Calculation Calculate reflection of sample by averaging results of two samples with one decimal.

Whiteness, relative = A/B*100%

 

 It is general accepted that whiteness is relative to a certain non-specific standard if not stated as absolute.
7. Notes The magnesium standard influences the relative readings. Absolute readings require the reflection of the magnesium oxide to be corrected against 100% reflection, but this turns out lower values not popular in the starch industry.  State result as absolute whiteness if reading is corrected to absolute whiteness. 

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