Researchers preserve cancer-fighting properties in frozen broccoli
By Darren Quick
August 7, 2013
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