This 2020 follow-on study to 3-day-old broccoli sprouts have the optimal yields investigated myrosinase enzyme activity:
“Myrosinase (MYR) can hydrolyze glucosinolates to produce sulforaphane [and other healthy compounds]. SF [sulforaphane] was extremely unstable during storage and it was best to enzymatically convert to SF before oral intake.
In this study, MYR activity in broccoli seeds and sprouts of different varieties were firstly compared. Then, after optimization for the microencapsulation condition of MYR, characteristics of free and encapsulated MYR enzyme were evaluated and compared.
The difference in MYR activity among seven broccoli varieties’ seeds was significant. However, total MYR activity in seeds and sprouts was actually not comparable. In the same weight of seeds and sprouts, dry matter content of sprouts was lower than that of seeds because of their high moisture content.
- MYR activity of sprouts did not change significantly during the first 2 days of germination.
- From the fourth day, enzyme activity increased significantly.
- By the sixth day, its activity increased to the maximum, then decreased.
Broccoli variety significantly affected MYR activity during germination. 6-day-old LW variety was selected for further research.
When temperature was higher than 55° C, free MYR activity decreased rapidly [but see Item 2 below]. At 65° C, the free enzyme activity was less than half of the maximum enzyme activity. Specific activity of encapsulated MYR declined slowly, with the values of 82.1% at 65° C.
Activity of free MYR was the highest at pH 5.0, and it decreased rapidly when pH was less or higher. Encapsulated MYR could retain its activity under wider pH range and higher temperature than free MYR. Encapsulated MYR also kept higher activity during storage at room temperature.
Supplement of encapsulated MYR was favorable for SF production in broccoli sprouts during storage.”
https://onlinelibrary.wiley.com/doi/10.1111/jfpe.13567 “Selection and microencapsulation of myrosinase enzyme from broccoli sprouts of different varieties and characteristics evaluation” (not freely available)
1. Human stomach pH is 1.5. This study didn’t measure myrosinase activity below pH 4, maybe because it’s inactivated? Don’t count on myrosinase hydrolyzing glucosinolates into sulforaphane and other isothiocyanates like I3C after swallowing broccoli sprouts or supplements.
2. These researchers’ previous study heated broccoli seed powder at 55°C for 5 min to inactivate the epithiospecifier protein. I thought about adjusting microwave practices for 3-day-old broccoli sprouts from ≤ 60°C to 55°C (131°F) in consideration of both the ESP and the 55-to-65°C decline in myrosinase activity.
But myrosinase activity at unmeasured 60°C isn’t at the graph’s straight line drawn between measured 55°C and 65°C. A substantial decline begins after 60°C, not after 55°C as drawn.
Consider this graphic from Enhancing sulforaphane content:
Myrosinase robustly hydrolyzes glucoraphanin into sulforaphane at 60°C. There’s clearly a myrosinase deactivation cliff between 60°C and 65°C.
3. Haven’t seen sulforaphane supplements with microencapsulated myrosinase. This study provided evidence to support that method. Less clear is whether microencapsulated myrosinase continues on intact past the stomach.
Even if there were such supplements, though, wouldn’t it be more efficient and effective to create broccoli sprout hydrolysis compounds just before eating them?
“Sulforaphane was extremely unstable during storage and it was best to enzymatically convert to sulforaphane before oral intake.”
Why depend on vendor claims, myrosinase stability, or our own individual metabolisms?