Like broccoli, cauliflower contains sulforaphane, which is easily lost through improper cooking. Boiling or blanching cauliflower causes the greatest loss of antioxidants, so your best bet appears to be steaming. Unfortunately, research has not identified ideal steaming times for cauliflower.
Moreover, research reveals different varieties of cauliflower respond differently to various levels of heat and cooking times. In one study, blanching purple cauliflower at 70 degrees C significantly increased sulforaphane content compared to 50 degrees C, while immersion time had no significant influence. In Roman cauliflower, on the other hand, both temperature and immersion time played a role.
Research shows steaming broccoli for three to four minutes is ideal, so I'd suggest using this as a general starting guideline for cauliflower as well. You can also boost the sulforaphane content of your cauliflower (as well as broccoli and other members of the cabbage family) by eating it with a myrosinase-containing food.
Facts Credit: mercola.com
