Harold McGee

Green Chlorophyll

Appears in
On Food and Cooking
On Food and Cooking

By Harold McGee

Published 2004

  • About
One change in the color of green vegetables as they are cooked has nothing to do with the pigment itself. That wonderfully intense, bright green that develops within a few seconds of throwing vegetables into boiling water is a result of the sudden expansion and escape of gases trapped in the spaces between cells. Ordinarily, these microscopic air pockets cloud the color of the chloroplasts. When they collapse, we can see the pigments much more directly.

Changes in chlorophyll during cooking. Left: The normal chlorophyll molecule is bright green and has a fat-like tail that makes it soluble in fats and oils. Center: Enzymes in the plant cells can remove the fat-like tail, producing a tailless form that is water-soluble and readily leaks into cooking liquids. Right: In acid conditions, the central magnesium atom is replaced by hydrogens, and the resulting chlorophyll molecule is a dull olive green.