1. Color Changes of Chlorophyll in Response to Changes in pH
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2. Introduction
In the subsequent slides the background color of the slide represents the color the pigment assumes under various conditions of pH.
Under more or less neutral conditions, chlorophyll has its normal vegetable green color (think of raw green beans or broccoli)

3. Chlorophyll

4. Acidic conditions
Under acidic conditions, the magnesium atom (Mg+2) is lost and the color changes to the characteristic pheophytin olive green color.

5. No Mg+2
atom
Pheophytin

6. Alkaline conditions
Under alkaline conditions the methyl and phytyl esters are removed, producing chlorophyllin which is a bright green color.

7. No ester
groups
Chlorophyllin

8. Chlorophyllase
Other reactions, mediated by the enzyme chlorophyllase, may result in changes in the pigment, even under conditions of frozen storage.
This is why such vegetables (green beans, broccoli, etc.) are blanched (put briefly in boiling water) before preservation by freezing. This destroys the enzyme activity.