Books and articles sometimes put it like this. Hojicha is not astringent because the heat of roasting destroys the astringent compounds. One sentence settles it, and the reader nods along.
What follows stands in front of that sentence with the figures gathered so far, and traces what has actually been measured.
Past the sentence that earned a nod
The book is closed partway, and a hand goes out to the cup. What has been measured goes as far as the compounds changing places.
Whether the new forms are astringent at hojicha strength has not been tested. The word “destroys” stands a step beyond what was measured.
The sources go as far as the swap. Next come the compounds that were actually tasted.
The epi forms on the tongue
A mouthful is held, waiting for anything left at the sides of the tongue. At tea strength, only the forms with “epi” have been tasted.
For one compound on the rising side, there is a study that rated its bitterness and astringency over time. That study, though, was not about tea. No study found here tests the rising forms at the strength and under the conditions of a hojicha infusion.
On top of that, a review notes that much about how astringency is sensed remains unclear. The sensation is thought to mix bitterness with a physical feel in the mouth. The sources go as far as saying the sense itself is still finding its footing. Next comes sweetness.