This 2020 Polish study investigated dried broccoli sprouts characteristics:

“The aim of this study was to quantify the air-drying and freeze-drying kinetics of broccoli sprouts. The Page model exhibited a very good fit to experimental data obtained by both air-drying and freeze-drying techniques. Time of germination had less effect on drying kinetics of broccoli sprouts.

Water activity (a_w) of fresh broccoli sprouts was 0.999 ± 0.03 and moisture content 82.6% (w.b.). Drying reduced the value of a_w (between 0.287 ± 0.04 (freeze-dried sprouts) and 0.293 ± 0.06 (air-dried sprouts at 40 °C)).

Highest total phenolics content and antioxidant activity were observed in air-dried sprouts (40 °C) and freeze-dried sprouts.

Drying curves of dried broccoli sprouts after 3 days of germination with experimental and predicted data based on the Page model: MR-moisture ratio, SPD40, SPD60 and SPD80-sprouts air-dried at 40, 60 and 80 °C, respectively, SPF-freeze-dried sprouts. [x axis in minutes]

Processes were continued until moisture of samples decreased to 10% (±0.5%) wet basis (w.b.).”

https://www.mdpi.com/2227-9717/8/1/97/htm “Drying Kinetics, Grinding Characteristics, and Physicochemical Properties of Broccoli Sprouts”

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Repeating a relevant section from Are sulforaphane supplements better than microwaved broccoli sprouts?, I contacted a distributor of a dried broccoli sprout powder. In correspondence the company founder said:

“Each 700 mg capsules yields around 15mg sulforaphane.”

The company founder has written several reviews, one of which was the 2016 Sulforaphane and Other Nutrigenomic Nrf2 Activators: Can the Clinician’s Expectation Be Matched by the Reality? Section 6.5 Sulforaphane stated:

“By calculation, MYR [myrosinase]-active whole broccoli sprout supplement yielding 1% SFN could deliver 10 mg SFN per gram of powder, corresponding to ~12 grams of fresh broccoli sprouts (dried powder retains ~8% moisture).”

I asked the current study’s lead coauthor for actual figures because eyeballing the above kinetics chart, the 60°C end point looks closer to 6% than 8%. No reply yet. 6% moisture content would give a 16.7-to-1 ratio.

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Per Week 18 of Changing to a youthful phenotype with broccoli sprouts, twice a day I start a new batch of broccoli sprouts with one tablespoon (10.7 grams) broccoli seeds of unspecified variety. Per Week 19, wet-basis (soaked five minutes then drained) weights of 3-day-old broccoli sprouts average 65.5 grams, consumed twice a day.

Let’s assume for calculation purposes:

• The 2016 review’s 12-to-1 ratio of fresh broccoli sprouts weight-to-dried broccoli sprout weight is fairly representative; and
• Recent 65.5 grams average of 3-day-old broccoli sprouts consumed twice a day is fairly representative.

Calculations based on personal correspondence:

• Sulforaphane yield of one vendor’s dried broccoli sprouts is 15 mg / 700 mg capsule = 2.14%.
• Using the review’s 12-to-1 ratio, a dried broccoli sprout equivalent of my daily consumption would be (65.5 g x 2) / 12 = 10.9 grams.
• A sulforaphane equivalent would be 10.9 g x 2.14% = 233 mg.

If I use this study’s “82.6% (w.b.)” rather than the review’s 12-to-1 ratio, a sulforaphane equivalent would be more than twice as much:

• A dried broccoli sprout equivalent of fresh broccoli sprouts would be (65.5 g x 2) x (1 – .826) = 22.8 grams.
• A sulforaphane equivalent would be 22.8 g x 2.14% = 488 mg.

These are both much too high. What isn’t right?

Subsequent investigation of a distributor’s site found this table:

The study referenced for equivalence was Sulforaphane treatment of autism spectrum disorder (ASD). Calculations:

• The 100 µmol sulforaphane amount for 90 kg participants weighed 17.73 mg per https://pubchem.ncbi.nlm.nih.gov/compound/sulforaphane.
• The equivalent broccoli sprout powder sulforaphane yield is 0.01773 / 3.6 g = 0.4925%. That’s 5 mg of sulforaphane per gram of broccoli sprout powder.
• 0.4925% / 2.14% = 0.23. Decrementing the above sulforaphane weights gives 233 mg x .23 = 54 mg, and 488 mg x .23 = 112 mg.

The answer to my question What isn’t right? I relied on private correspondence rather than what a vendor publicly disclosed.

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I’m not particularly concerned about analytical uncertainties for myself. Whatever the numbers are, microwaving techniques for fresh broccoli sprouts increase them.

I immerse 3-day-old broccoli sprouts in 100 ml distilled water, then microwave them on 1000W full power for 35 seconds to ≤ 60°C (140°F) per Microwave broccoli to increase sulforaphane levels. After microwaving I transfer broccoli sprouts to a strainer, and wait five minutes to allow further myrosinase hydrolization of glucoraphanin and other glucosinolates into sulforaphane and other healthy compounds.

Broccoli sprout drying techniques don’t increase sulforaphane content as does microwaving. A broccoli sprout powder vendor has to take care that their drying process doesn’t hydrolyze glucosinolates, because sulforaphane degrades quickly unless it’s stabilized.

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A study compared in Measuring sulforaphane plasma compounds used a stabilized product made from broccoli seeds. One of that study’s findings was:

“We evaluated stability of SF concentration in these tablets when maintained at -20 °C. Decline in SF content in 2 separate lots, shipped in boxes containing blisterpacks of tablet measured over 1.5 years, equates to about 17.8% per year.”

Those researchers stipulated a sulforaphane amount of 94.4 μmol in two tablets given to study subjects. The sulforaphane amount would have been (1 / 0.1773 mg) x 10 mg x 2 = 112.8 μmol if that study’s researchers had found the labelled 10 mg sulforaphane weight in each tablet.

The product’s sulforaphane stabilized for a short time, yes. But it measurably degraded over 1.5 years despite favorable storage conditions.

Wouldn’t it be better to create broccoli sprout hydrolysis compounds by microwaving them just before eating, rather than depending on vendor claims or individual metabolism?