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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.
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| 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