Why are these pigments unstable in the presence of light or heat energy?

Answer 1

Chlorophyll: Reaction with heat depends on pH.

In a basic solution (pH 9), chlorophyll is stable, and

in an acidic solution (pH 3) it is unstable. When

heated, the cell membrane of the plant deteriorates,

releasing acids, which decrease the pH. This results

in the magnesium atom being displaced by two

hydrogen ions, resulting in the formation of olivebrown pheophytin complex. This cell degradation

during heating also makes the chlorophyll more

susceptible to photo-degradation.

*When chlorophyll undergoes heat process, it will turn dull olive brown.

Answer 2

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