Broccoli got a bum rap when President George H.W. Bush declared that he didn’t like it and never again wanted to see it served in the White House or on Air Force One. I hope you don’t share his aversion, because broccoli is super-healthful. It’s high in fiber, folate, vitamin C and antioxidants…and because it contains a cancer-fighting compound called sulforaphane, eating just a few servings per week can reduce your cancer risk.
But: If you buy your broccoli frozen, you don’t get the full benefits—because the prefreeze processing and typical cooking method destroy the vegetable’s anticancer properties.
Cool new discovery: There’s a simple trick you can use to restore frozen broccoli’s super powers, a recent study reveals.
A DELICATE BALANCE
Bear with me while I explain some basic broccoli chemistry and the trial-and-error process the researchers used to come up with this discovery.
You know the pungent odor that fills your kitchen when you throw broccoli scraps in the trash? That smell comes from all the sulfur compounds, one of which is the sulforaphane responsible for broccoli’s ability to combat cancer. When you eat fresh broccoli, you get lots of sulforaphane, provided you eat it raw or nearly raw (for instance, steamed for no more than three to five minutes). But when broccoli is frozen, the sulforaphane is lost. Here’s why…
Sulforaphane is created when another compound found in broccoli, glucoraphanin, comes in contact with one of broccoli’s enzymes, myrosinase. This contact occurs when broccoli is chewed or chopped. Typically, before broccoli is frozen, commercial vegetable processors extend its shelf life by blanching it at a very high temperature (typically above 200°F) to inactivate its peroxidase, an enzyme thought to cause broccoli to degrade over time. Unfortunately, this high heat also inactivates the myrosinase—thus rendering the glucoraphanin incapable of creating sulforaphane.
Researchers at the University of Illinois tried to get around this problem by blanching broccoli at a lower temperature before freezing it. They discovered that blanching at 169°F did preserve most of the myrosinase. Yet after this blanched broccoli was frozen and then cooked, the researchers found that no sulforaphane formed. They realized that this is because the typical instructions for cooking frozen broccoli are to microwave it—which again raises the temperature too high and/or for too long. In other words, the myrosinase in frozen broccoli gets hit with a double whammie from both the blanching and the microwaving. (Note that, even with fresh broccoli, cooking the vegetable too long inactivates the myrosinase.)
So then the researchers took a different approach. Instead of worrying about blanching temperatures or cooking methods, they instead added an outside source of myrosinase—a bit of ground freeze-dried daikon radish (a mild-flavored radish that looks sort of like a fat white carrot)—while the frozen broccoli was being cooked. The amount of radish powder the researchers added was too little to change the taste or appearance of the broccoli, but it provided enough myrosinase to allow the interaction with glucoraphanin, triggering the formation of sulforaphane. Thus the frozen broccoli’s cancer-fighting properties were restored!
TRY THIS AT HOME
Hopefully, commercial food processors will catch on to this new technique for preserving frozen broccoli’s full nutritional punch and start sprinkling on some daikon powder at the processing plant. Until that happens, though, you can easily perform this bit of food magic yourself at home.
Simply add some freeze-dried daikon (comparable to the amount of salt you’d normally add) to your frozen broccoli either before or after cooking it. You can find daikon radish (also called white radish) at Asian grocery stores, Whole Foods stores or online. Another option: Whenever you eat broccoli that has been frozen, in the same meal include another outside source of myrosinase, such as raw red radishes, cabbage slaw or watercress…or eat one-quarter teaspoon of horseradish, wasabi or mustard along with your serving of broccoli.