Does microwaving broccoli preserve the myrosinase enzyme? | Jed W. Fahey
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Myrosinase is a heat-sensitive enzyme that rapidly denatures during normal cooking processes. Adding ground mustard seed (which is rich in myrosinase) to cooked vegetables provides a culinary workaround to myrosinase losses incurred during cooking. Food preparation techniques that employ shorter cooking times and less water – such as microwaving – favor myrosinase stability and retention – potentially enhancing sulforaphane production. In this clip, Dr. Jed Fahey discusses whether or not microwaving broccoli preserves the heat-sensitive myrosinase enzyme enough to convert glucoraphanin into sulforaphane.
[Dr. Patrick]: Okay, so let's move on to the next question, and the question has to do with a recent study that claimed microwaving broccoli was able to increase levels of sulforaphane in the broccoli.
[Dr. Fahey]: Yeah.
[Dr. Patrick]: What are your thoughts on that study?
[Dr. Fahey]: Rhonda, I don't like being negative about other people's studies, but I don't like it. So respectfully, you know, I think they said a number of things that were...that are misleading. Maybe not wrong, but they sort of get you down the wrong garden path to truth.
So first of all, when you harvest broccoli sprouts or broccoli, you or a farmer, they don't have any sulforaphane in them, they don't have any free sulforaphane, it's all glucoraphanin, which is the precursor of sulforaphane. Myrosinase converts one to the other. It happens when you start chewing, it happens in your gut, we've talked about that.
Microwaving is merely a gentle method by which one cooks and you can try to minimize denaturing or destruction of myrosinase with microwaving. And there's evidence that there's...you know, you may not completely wipe out the myrosinase if you don't get the internal temperature of the food product up above 70 or 80 degrees centigrade, Celsius. Microwaving also gives you minimal leakage of plant juice. So, you know, when you steam the hell out of something or boil a vegetable, you know, most of the goodies come out in the wash, they come out in the pot liquor, right?
So microwaving is useful there. But they state... I don't have it in front of me. They state something like "increase the levels of sulforaphane in broccoli." You do not increase the levels of either sulforaphane or glucoraphanin by a cooking method whatever. You may enhance it... You may retard its destruction, you may retard its loss or limit its loss.
But the other thing is they have a couple of figures in that paper that suggest, and, you know, I should talk to the authors perhaps and take my beef to them, but they suggest that the controls have far less glucoraphanin in them than the treatments, the different microwave times. That can't be so, it's impossible. I promise you that. You don't create glucoraphanin out of whole cloth, you don't magically create it.
So I'm not very...there's enough that worries me about that paper that I would sort of steer clear of it and just say, yeah, indeed microwaving, if you're going to cook broccoli, microwaving is probably the best way to do it. Minimal microwaving, make it nice and a little tender and soft, and minimize the leakage of compounds into the pot liquor, or else incorporate that into whatever you're eating. And that's the way I make broccoli. You know, rinse it, put it in the Corning dish, put it in the microwave until it just gets a little less crunchy, and eat it. And there's basically nothing in the bottom. And I put lemon juice on it.
[Dr. Patrick]: I do the same thing, I microwave my broccoli, but I put mustard seed powder. And just an FYI for everyone viewing right now or listening. When that paper came out, the first thing I did was e-mail Jed and I was like, "What do you think of this paper?"
[Dr. Fahey]: What did I say? I forgot.
[Dr. Patrick]: Oh, you weren't...you were probably less PC about it to me. But thanks for your expert opinion on that, I think that can be...that is a misleading study.
A glucosinolate (see definition) found in certain cruciferous vegetables, including broccoli, Brussels sprouts, and mustard. Glucoraphanin is hydrolyzed by the enzyme myrosinase to produce sulforaphane, an isothiocyanate compound that has many beneficial health effects in humans.
An essential mineral present in many foods. Iron participates in many physiological functions and is a critical component of hemoglobin. Iron deficiency can cause anemia, fatigue, shortness of breath, and heart arrhythmias.
A family of enzymes whose sole known substrates are glucosinolates. Myrosinase is located in specialized cells within the leaves, stems, and flowers of cruciferous plants. When the plant is damaged by insects or eaten by humans, the myrosinase is released and subsequently hydrolyzes nearby glucosinolate compounds to form isothiocyanates (see definition), which demonstrate many beneficial health effects in humans. Microbes in the human gut also produce myrosinase and can convert non-hydrolyzed glucosinolates to isothiocyanates.
An isothiocyanate compound derived from cruciferous vegetables such as broccoli, cauliflower, and mustard. Sulforaphane is produced when the plant is damaged when attacked by insects or eaten by humans. It activates cytoprotective mechanisms within cells in a hormetic-type response. Sulforaphane has demonstrated beneficial effects against several chronic health conditions, including autism, cancer, cardiovascular disease, diabetes, and others.
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