Does Heat Destroy Myrosinase? Why Processing Matters Before You Buy Broccoli Sprout Powder

Picture a tray of fresh young broccoli sprouts just before they are processed. Inside that fresh plant material are glucoraphanin and myrosinase, two parts of the natural chemistry that can lead to sulforaphane.

Now follow those sprouts through drying, milling and encapsulation. The important question is not only how warm they became. It is this: when the finished capsule reaches you, is active myrosinase still there?

Yes, sufficient heat can reduce or inactivate myrosinase. But there is no single honest temperature that can be applied to every broccoli sprout powder. The effect depends on temperature, how long the material is exposed, the plant tissue, moisture level and the processing conditions. That is why, at Kiwi Superfoods, we think finished-product verification matters more than a simple temperature claim.

Start with a fresh sprout, not a supplement label

Fresh broccoli sprouts naturally contain glucoraphanin and myrosinase. Myrosinase is an enzyme, so it can be affected by heat and other processing conditions.

This matters when fresh sprouts are turned into a shelf-stable supplement. A label may tell you how much broccoli sprout material is in a capsule, but that number alone cannot tell you how much active enzyme made it through processing.

Our Kiwi Superfoods Broccoli Sprout Powder starts with 100% NZ-grown, lightly milled broccoli sprouts. We air-dry the sprouts and, importantly, test the finished material to confirm that active myrosinase remains present.

The first thing processing can change is the enzyme

You do not need a biochemistry lesson to understand why this matters. Glucoraphanin is a precursor found in broccoli sprouts. Myrosinase helps convert glucoraphanin into sulforaphane when the plant material is disrupted and the two can interact.

Because myrosinase is an enzyme, processing can change its activity. It is possible for a dried broccoli ingredient to retain substantial glucoraphanin while having less active myrosinase than the fresh plant material it came from.

That is the useful distinction. Seeing glucoraphanin on a label does not automatically tell you the status of the enzyme. If you want the deeper explanation of why two apparently similar doses can behave differently, see our guide to sulforaphane bioavailability.

There is no single magic temperature

If you search what temperature destroys myrosinase, it is tempting to want one clean number. The research does not support one universal cut-off for every broccoli product.

Published experiments use different plant tissues, heating times, moisture levels and processing conditions. Studies in mature broccoli have reported very large losses of myrosinase activity after sustained higher-temperature treatment. Other work has found different thermal behaviour in young broccoli sprouts. Research also shows that water content can change the rate at which broccoli myrosinase loses activity during heating.

That means a result from a broccoli floret heated for a set time in a laboratory cannot simply be transferred to a young sprout moving through a commercial drying process. Even two studies using the same stated temperature may not be testing the same thing if the exposure time, moisture or plant structure is different.

So the useful answer is not a magic number. Myrosinase is heat-sensitive, and both temperature and exposure conditions matter.

Now follow the sprouts into the drying room

Fresh sprouts contain a lot of water. To turn them into a shelf-stable powder, that moisture needs to be reduced. This is where the question changes from cooking science to supplement processing.

Drying does not automatically destroy myrosinase, and air drying does not automatically preserve all of it. Research on broccoli dehydration shows that myrosinase activity can change during drying, with temperature, moisture and the physical state of the plant material all playing a part.

That is why the words air-dried or gently dried are useful context, but they are not the whole answer. The more useful question comes after drying: what enzyme activity is still present in the finished material?

The process description tells you how it was made. Testing tells you what survived.

Imagine three jars on a shelf.

The first says broccoli powder and gives you a large milligram number. That tells you the weight of powder, but not whether active myrosinase is still present.

The second talks about gentle processing. That sounds relevant, and it is, but the process description still does not directly confirm the status of the finished enzyme.

The third tells you where the broccoli came from, how it was processed and that active myrosinase was checked in the finished material. If myrosinase is something you specifically care about, that last piece gives you more useful information.

Finished-product testing does not guarantee identical sulforaphane absorption or the same outcome for everyone. Human studies show that active myrosinase can influence sulforaphane availability in the preparations studied, but individual absorption still varies. What finished-product testing can answer is a manufacturing question: after processing, is active myrosinase still detectable in the material?

We test after the drying is done

For our Broccoli Sprout Powder, we use 100% NZ-grown, lightly milled broccoli sprouts. We air-dry them and keep the drying temperature as low as practical.

We do not give you a simplistic drying-temperature claim. The core temperature of an individual broccoli sprout is difficult to measure precisely while it is being processed, so we do something we think is more useful: we test the finished product.

Our finished material is independently tested to confirm glucoraphanin levels and myrosinase activity. We guarantee glucoraphanin and active myrosinase in the finished product. You can also read our Broccoli Sprout Powder FAQ for more on how we approach drying and testing.

A daily serve is 2 x 600 mg capsules and is made from approximately 12 g of fresh broccoli sprout starting material. Our finished-product specification gives a guaranteed minimum of 6 mg sulforaphane per daily dose.

That 6 mg specification should not be read as a promise that every person absorbs exactly 6 mg. Absorption varies. For us, the important point here is that we do not ask you to judge the product from the drying description alone. We verify the finished material after processing.

What this means when you are choosing a powder

Scenario one: You see a large broccoli powder milligram number, but nothing about myrosinase. The weight tells you how much powder is there. It does not tell you whether active enzyme survived processing.

Scenario two: You see a gentle-processing claim, but no confirmation of finished-product myrosinase. That processing language is useful context, but it is not the same as checking the finished material.

Scenario three: You can see the broccoli source, the processing approach and verification that active myrosinase remains in the finished product. That gives you a clearer picture of what you are actually buying.

If you are comparing the wider market, our guide to choosing sulforaphane powder in NZ covers the broader buying question without treating every broccoli product as if it were made the same way.

Common questions

Does heat destroy myrosinase?

Yes. Sufficient heat can reduce or inactivate myrosinase. The amount of activity lost depends on factors such as temperature, exposure time, plant tissue, moisture and processing conditions, so the effect is not captured by one temperature alone.

What temperature destroys myrosinase?

There is no single honest universal threshold. Published studies show myrosinase activity declining under different combinations of temperature and time, and results also vary with the broccoli tissue, moisture level and test method. A temperature reported in one experiment should not be treated as a universal cut-off for every broccoli sprout powder.

Does drying broccoli sprouts destroy myrosinase?

Not necessarily. Drying can change myrosinase activity, but the result depends on how the sprouts are dried, including temperature, time, moisture changes and the condition of the plant material. The most useful question is what active myrosinase remains after drying is complete.

Is air drying better for preserving myrosinase?

Air drying can be used under conditions intended to protect enzyme activity, but the drying method alone is not proof that all myrosinase survived. Finished-product testing is more useful because it checks what remains after processing.

Can myrosinase survive processing?

Yes, active myrosinase can remain after processing when conditions are suitable. How much activity remains depends on the material and the processing conditions, which is why verification of the finished product is valuable.

Why does active myrosinase matter in broccoli sprout powder?

Myrosinase helps convert glucoraphanin into sulforaphane. If you are choosing a broccoli sprout powder because you care about that natural conversion step, knowing whether active myrosinase remains gives you more useful information than powder weight alone.

How can I tell whether a broccoli sprout powder still has active myrosinase?

Look for a clear finished-product statement about active myrosinase or testing that confirms enzyme activity after processing. A drying description can be helpful, but it does not directly tell you what survived.

Does Kiwi Superfoods test myrosinase after drying?

Yes. We test our finished Broccoli Sprout Powder to confirm that myrosinase remains present and active after processing. Our finished material is independently tested for both glucoraphanin levels and myrosinase activity.

The processing detail we think is worth checking

How a broccoli sprout product was processed matters. What is still present after processing matters more.

If you are looking specifically for an NZ-grown whole-sprout product with verified active myrosinase, our Broccoli Sprout Powder gives you that information clearly. It is made from 100% NZ-grown, lightly milled broccoli sprouts, air-dried, then checked in the finished form for glucoraphanin and active myrosinase.

As with any supplement, use it as directed. If you are pregnant or breastfeeding, have a thyroid condition, or are unsure whether it suits your medicines or health needs, check with a qualified health professional.

References

1. Effect of water content and temperature on inactivation kinetics of myrosinase in broccoli. Food Chemistry, 2014.
2. Impact of different drying trajectories on degradation of nutritional compounds in broccoli. LWT - Food Science and Technology, 2014.
3. High-Pressure Processing of Broccoli Sprouts: Influence on Bioactivation of Glucosinolates to Isothiocyanates. Journal of Agricultural and Food Chemistry, 2017.
4. Sulforaphane Bioavailability from Glucoraphanin-Rich Broccoli: Control by Active Endogenous Myrosinase. PLOS ONE, 2015.