We did about a dozen different teas a few weeks ago.
And sloshed in cream, and let the tea sit for a few hours. Then we checked just how thick the protein-tannin -rings were on the sides of the cups. (protein from the cream, tannin from the various teas: they combine, which is why you get rings in your milked-up coffee and black tea. It's as easy to uncombine them as it is to uncook boiled eggs ...)
Here's a pretty picture of the dry herbs, measured out into cups:
Pic: Astringency test herbs in cups.
- schisandra berries, Schisandra chinensis, 20 g
- yellowdock root, Rumex sp., 20 g
- redroot, Ceanothus sp., 20 g
- roseroot, Rhodiola rosea, 20 g
- uva-ursi leaf, Arctostaphylos uva-ursi, 5 g
- alder cones, Alnus sp., 5 g
- horsechestnut leaf, Aesculus hippocastanum, 5 g
- normal black tea, 5 g
- ladies' mantle leaf, Alchemilla vulgaris, 5 g
- cornflower, Centaurea cyanus, 5 g
- red clover flowers, Trifolium pratense, 5 g
- (normal coffee), 5 g
- goldenrod flowers, Solidago virgaurea, 5 g
- black currant leaf, Ribes nigrum, 5 g
- calendula petals, Calendula officinalis, 5 g
Add 2 dl boiling water and let sit for 20-25 minutes. Here's a pretty picture of those infusions:
Pic: Astringency test teas, infusing.
Strain, measure out 1 dl strained tea per herb, and add 1 tablespoon cream to each cup. Let sit for 4 hours, and check how thick the rings on the sides of the cups are.
Here's a pretty pic of the strained-out teas:
Pic: Astringency test teas, strained.
The schisandra was so sour that it curdled the cream, and didn't make rings at all. That was full-fat cream ... 38 % fat.
I took pictures of the creamed-up teas, too, but they didn't amount to much, seeing that we used white cups ... it was all just an almost uniform whiteness, in the photos. Note to self: next time, use clear drinking glasses; that way, you can see the rings better, too.
And drat it, I know I wrote down which herbs were the strongest astringents in this particular test (= gave the thickest rings), but I'll have to send an email to one or the other of the students in that class, cos I just can't find my notes on it.
The strongest were, in descending order, something like: alder, rumex, uva-ursi, aesculus, rhodiola - but I'm not sure.
As a bonus you get a pic of the dried yellowdock root, all soaked up: woot, it's partly yellow! Airdried root isn't yellow at all, it's just a dark reddish-brown.
Pic: Soaked yellowdock root shows its yellow color.
(And for those using outdated measuring systems: g is gram, 1/1000 of a kg, which is kilogram. dl is deciliter, 1/10 of a liter.)
Related entry: Tannins
Update 10May06: Hah, found my notes. It's:
Strongest: alder cones
Next strongest: horsechestnut leaf and yellowdock root.
Next strongest: coffee, tea
Next strongest: ladies' mantle, cornflower and calendula.
Surprising, eh? I expect the uva ursi would give another reading if we had boiled things (= decoction), instead of just pouring boiling water over them (= infusion).