Page 87 - Statistics presented by Dr. Sara Ismail Aborass

9/8/2023

Rancidity
Kreis-Kerr test
The presence of aldehyde as epihydrine aldehyde (measured by Kreis-Kerr
test) indicates Progressive Rancidity

Test
Oil or fat sample + phloroglucinol/ conc HCl → pink color indicate rancidity
Epihydrine aldehyde + phloroglucinol/ conc HCl → condensation product

"pink color

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Chemical
examinations

Acid value AV Saponification value Ester Value Iodine Value Rancidity
SPV

FFA FFA + combined FA Combined FA C=C Epihydrine aldehyde

Direct Titration ≠ Back Titration: Xss =SPV-AV Back Indirect + phloroglucinol/
Base using Ph.Ph Base remaining iodometric titration: conc HCl 
Pink colour
Base ≠ Acid C=C+IBr /ICl

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