What about frozen broccoli and other crucifers? Commercially produced frozen broccoli lacks the ability to form sulforaphane because the vegetables are blanched (flash-cooked) before they’re frozen for the very purpose of deactivating enzymes.11 This process prolongs shelf life, but when you take the veggies out of your freezer, the enzyme is inert. At that point, it doesn’t matter how much you chop or how long you wait—no sulforaphane is going to be made. This may be why fresh kale has been shown to suppress cancer cell growth in vitro up to ten times better than frozen kale.
