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International Starch Institute
Science Park Aarhus, Denmark
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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Keywords: laboratory method determination whiteness starch reflection