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SOP: Characterization of Chlorophyll by the Brown Phase Reaction

GIFSQ — Global Institute for Food Safety & Quality

Principle

The “brown phase reaction” characterizes chlorophyll in products when the chlorophyll has not previously been treated with alkalies: a green ether or petroleum ether solution of the colouring matter turns brown on treatment with methanolic KOH and quickly returns to green.

Apparatus required

  • Test tube

Reagents

a. Ether or petroleum ether (solvent for the colouring matter).

b. 10% solution of KOH in methanol.

Procedure

Prepare a green ether or petroleum ether solution of the colouring matter

↓

Treat with a small quantity of 10% solution of KOH in methanol

↓

The colour becomes brown, quickly returning to green — this characterizes chlorophyll, provided the chlorophyll has not been previously treated with alkalies

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.