Things Required:
A few broccoli stalks or a small zucchini
Pot of boiling water
Directions:
Cut off the stem and separate the broccoli flowers. Place the flowers in a pot of boiling water. After 30 seconds, scoop out half the broccoli. Let the rest continue to cook.
This Is What Happens:
During the first 30 seconds, the broccoli turns a deep green. The broccoli left in the water loses colour.
Science Behind It:
The colour intensifies because gases trapped in the spaces between cells suddenly expand and escape. Ordinarily, these air pockets dim the green colour of the vegetable. But when heat collapses the air pockets, we can see the pigments much more clearly.
Longer cooking, however, results in a chemical change. The chlorophyll pigment that makes vegetables green reacts to acids. Water is naturally a little acid. When we heat broccoli or zucchini or spinach, its chlorophyll reacts with its own acids and the acids in the cooking water forms a new brown substance (pheophytin). That’s what makes some cooked broccoli an ugly olive green.
