Broccoli seed

Broccoli seeds are minute, round, reddish-brown to blackish seeds, about the size of a pinhead, like those of mustard or cabbage. They are produced in slender pods after the broccoli plant bolts and flowers.

They are not eaten dry. They are soaked and sprouted for three to six days to give small green stems with two tiny leaves, which taste peppery, fresh and a little like radish or cress.

Sprouting seeds are sold as untreated packets or loose bulk from seed companies and are also used for broccoli sprout powders and extracts in the supplement trade.

Broccoli was developed from wild cabbage, Brassica oleracea, in the Mediterranean and probably selected by Etruscan or Roman farmers in Italy for its edible flower head. Its name derives from Italian broccolo, meaning a cabbage sprout or flowering top, from broccus, a Latin word for a projection.

The seed crop is produced in temperate regions where broccoli will bolt and set seed, such as in Italy, the Netherlands, Denmark and parts of the United States.

Sprouting broccoli seed is grown for the sprouting trade and sold separately from seed for commercial vegetable growers.

Broccoli as a vegetable was known in Roman Italy and became popular in Italian and later English and American cooking. Eating its seeds as sprouts is a more recent idea, mainly arising from research in the 1990s.

In 1992, a team at Johns Hopkins University led by Paul Talalay identified sulforaphane, a compound that induces protective enzymes in cells, as a major active component of broccoli. In 1997, the group reported that three-day-old broccoli sprouts contained far higher levels of its precursor, glucoraphanin, than the mature vegetable.

The finding led to the marketing of broccoli sprouts in health food stores and to a wide field of research into the effects of sulforaphane, with trials looking at autism, diabetes, cancer prevention and respiratory health, so far with mixed or preliminary results.

Food safety authorities have also warned that raw sprouts of all kinds can carry bacteria, since the warm, damp conditions of sprouting also favour microbial growth.

Sprouted broccoli seeds are eaten raw in salads, sandwiches, wraps and sushi, stirred into soups at the end of cooking, or blended into smoothies. Their peppery crunch is a good garnish.

Broccoli seed or sprout powders and extracts are sold as supplements, and some producers standardise them to glucoraphanin content.

Home sprouters usually soak the seeds in water for several hours and rinse them twice a day in a jar or tray for around four days. Sprouts keep for about a week in the refrigerator, and a few days of growing in light turns them green.

Broccoli sprouts supply glucoraphanin, which, when the sprouts are chewed or crushed, is converted by the enzyme myrosinase into sulforaphane. Laboratory work shows that sulforaphane activates antioxidant defence pathways, and small human trials have explored effects on blood sugar, inflammation and detoxification of air pollutants.

Results are promising but preliminary, and there is no firm proof that eating sprouts prevents or treats a disease. Cooking at high heat can destroy the enzyme and lower sulforaphane yield.