The New Complete Book of Food
To keep broccoli green, you must reduce the interaction between the chlorophyll and
the acids. One way to do this is to cook the broccoli in a large quantity of water, so the acids
will be diluted, but this increases the loss of vitamin C.* Another alternative is to leave the
lid off the pot so that the hydrogen atoms can float off into the air, but this allows the smelly
sulfur compounds to escape, too. The best way is probably to steam the broccoli quickly
with very little water, so it holds onto its vitamin C and cooks before there is time for reac-
tion between chlorophyll and hydrogen atoms to occur.How Other Kinds of Processing Affect This Food
Freezing. Frozen broccoli usually contains less vitamin C than fresh broccoli. The vitamin
is lost when the broccoli is blanched to inactivate catalase and peroxidase, enzymes that
would otherwise continue to ripen the broccoli in the freezer. On the other hand, according
to researchers at Cornell University, blanching broccoli in a microwave oven—two cups of
broccoli in three tablespoons of water for three minutes at 600–700 watts—nearly doubles
the amount of vitamin C retained. In experiments at Cornell, frozen broccoli blanched in a
microwave kept 90 percent of its vitamin C, compared to 56 percent for broccoli blanched in
a pot of boiling water on top of a stove.Medical Uses and/or Benefits
Protection against some cancers. Naturally occurring chemicals (indoles, isothiocyanates,
glucosinolates, dithiolethiones, and phenols) in Brussels sprouts, broccoli, cabbage, cauli-
flower, and other cruciferous vegetables appear to reduce the risk of some forms of cancer,
perhaps by preventing the formation of carcinogens in your body or by blocking cancer-
causing substances from reaching or reacting with sensitive body tissues or by inhibiting the
transformation of healthy cells to malignant ones.
All cruciferous vegetables contain sulforaphane, a member of a family of chemicals
known as isothiocyanates. In experiments with laboratory rats, sulforaphane appears to
increase the body’s production of phase-2 enzymes, naturally occurring substances that inacti-
vate and help eliminate carcinogens. At the Johns Hopkins University in Baltimore, Maryland,
69 percent of the rats injected with a chemical known to cause mammary cancer developed
tumors vs. only 26 percent of the rats given the carcinogenic chemical plus sulforaphane.
To get a protective amount of sulforaphane from broccoli you would have to eat about
two pounds a week. But in 1997, Johns Hopkins researchers discovered that broccoli seeds
and three-day-old broccoli sprouts contain a compound converted to sulforaphane when
the seed and sprout cells are crushed. Five grams of three-day-old sprouts contain as much
sulphoraphane as 150 grams of mature broccoli.* Broccoli will lose large amounts of vitamin C if you cook it in water that is cold when you start. As it
boils, water releases oxygen that would otherwise destroy vitamin C, so you can cut the vitamin loss
dramatically simply by letting the water boil for 60 seconds before adding the broccoli.