Researchers preserve cancer-fighting properties in frozen broccoli


August 7, 2013

Researchers have found a simple way to preserve broccoli’s cancer-fighting properties after freezing (Image: Shutterstock)

Researchers have found a simple way to preserve broccoli’s cancer-fighting properties after freezing (Image: Shutterstock)

Broccoli is one of those foods we’re told to eat as youngsters because it’s good for us. Unfortunately, researchers at the University of Illinois (U of I) found some of that goodness, namely the vegetable’s cancer-protective benefits, doesn’t survive the process its subjected to before reaching the freezers at supermarkets. Thankfully, the researchers followed up their initial research and found a simple way to preserve broccoli’s cancer-fighting properties.

Before broccoli is frozen and packaged, it is standard industry practice to first heat the vegetable to 86° C (187° F) in a process known as blanching to inactivate enzymes that can affect its color, taste and smell over its 18-month shelf life. But Elizabeth Jeffery, a U of I professor of nutrition, and her team found that this process also destroys the enzyme myrosinase which, when brought into contact with glucoraphanin when raw broccoli is chopped or chewed, forms broccoli’s cancer-preventive compound, sulforaphane.

“We know this important enzyme is gone because in our first study we tested three commercially frozen broccoli samples before and after cooking,” says Edward B. Dosz, a graduate student in Jeffery’s laboratory. “There was very little potential to form sulforaphane before the frozen broccoli was cooked and essentially none after it was cooked as recommended.”

But any young upstarts looking for an excuse to leave broccoli on the side of their plate may need to think again. In their second study, the team experimented with heating the vegetable to a slightly lower temperature of 76° C (169° F) and found that 82 percent of the enzyme myrosinase was preserved without affecting the frozen vegetable’s safety or quality.

Additionally, by sprinkling already frozen broccoli with 0.25 percent of daikon radish, another vegetable that contains myrosinase and was undetectable to the eye or the taste buds in such small amounts, the researchers were able to maintain raw broccoli’s cancer-fighting properties after cooking.

“That means that companies can [heat] and freeze broccoli, sprinkle it with a minute amount of radish, and sell a product that has the cancer-fighting component that it lacked before,” says Dosz. “We were delighted to find that the radish enzyme was heat stable enough to preserve broccoli’s health benefits even when it was cooked for 10 minutes at 120° F (49° C). So you can cook frozen broccoli in the microwave and it will retain its cancer-fighting capabilities.”

So although the researchers hope food processors will adopt the lower temperature process, Jeffery says that until they do, consumers can help boost frozen broccoli’s health benefits by sprinkling it with a related cruciferous vegetable, such as raw radishes, cabbage, arugula, watercress, horseradish, spicy mustard, or wasabi, before cooking. I’m sure the kids will love it.

The team’s studies, which were funded by the US Department of Agriculture (USDA) and the National Institute of Food and Agriculture (NIFA), are published in the Journal of Functional Foods and the Journal of Food Science.

Source: University of Illinois

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

A splendid list: raw radishes, cabbage, arugula, watercress, horseradish, spicy mustard, and wasabi. They all taste better than broccoli, so why bother with the fractal greens in the first place?


How can the brocoli remain uncooked when having been exposed to such high tempeatures ??


Where would one find out which food processors use this low temperature process?

Chris Lozeau

Once again, raw foods beat out pre-packaged foods for nutritional value.

Larry Hooten

Chris: No one does, yet. Until then, you can get all the benefit of broccoli by eating raw florets. I suggest in salad. All you should taste is the dressing. No matter. You will soon get over any taste aversion.

Geometter: Because broccoli is the highest in nutrition.

rvgans: It is cooked. The article was confusing on that. The important point to remember is to cook it below 169 degrees. I recommend stopping as soon as it turns a bright green, dark is overdone.

The stalk is cheaper and can be used by peeling it until soft. Asparagus is the same. I use a potato peeler.

Don Duncan

Who cooks green vegetables at such low temperatures? Most people either boil or steam or microwave, and all without any precise temperature control.

This is a great idea but the benefits will be lost on most people unless they have a Sous Vide setup.

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