Very interesting. Thanks

The white oak family tend to have much lower tannin levels than the red oak group. Quercus emoryi may have very low tannin levels compared to other red oaks, but I personally doubt it is lower in tannin than white oaks like Q. rugosa and Q. arizonica.

One study looking at the acorns of Q. emoryi found 460 mg catechin and 22,896 mg hydrophilic phenolics per 100 g. (Both of these can be considered tannins)

(source: Chemical Composition and In Vitro Bioaccessibility of Antioxidant Phytochemicals from Selected Edible Nuts, Jazmín C Stevens-Barrón)

Another study of Q. rugosa heartwood found relatively low tannin content at about 0.3 % to 2 %.

(source: Determinación de compuestos fenólicos y capacidad antioxidante en bellota (Quercus rugosa))

For comparison, Q. robur wood has a tannin content of about 6%, while the acorns contain 20,400 mg tannin per 100 g (including 11, 760 catechin).

If we assume that the ratio of tannins in the wood relative to the acorns in Q. rugosa is similar to that for Q. robur (which to be fair is a big assumption, but is also reasonable), then we can roughly calculate that the acorns of Q. rugosa would have around between 1020 to 6800 mg of tannin per 100 g. This is a little more than three times lower than for Q. emoryi.

Although this is a very rough napkin paper calculation, it suggests that Q. rugosa acorns may likely be even much lower in tannin than Q. emoryi. That really wouldn't be surprising to me, since the white oaks very much tend to have less tannin than red oaks, and also these oak species from arid areas do not need as much tannin, since rot and fungal attack is unlikely in the dry conditions. But paradoxically, Q. emoryi tends to grow in drier areas of Arizona than Q. rugosa, and we might expect that acorns of Q. emoryi to have a higher tannin level as a defense mechanism, to make animals a little less likely to eat them, so the seeds would have more time to get established, until the next monsoon rain comes. Whereas for Q. rugosa the tree would probably produce a bigger flush of acorns and be surrounded by other food sources.

I hope that's not too complicated of a line of reasoning to make a speculative point, I have a habit of doing that.

(Edit: unfortunately to make this even more complicated, depending on how I am reading that study, they might only have measured 460 mg of condensed tannins, as opposed to hydrolysable tannins, the other tannin type, in Q. emoryi, with red oak species in general often having about 11 times more hydrolysable tannin than condensed tannin in their acorns.)

LOL!

Sorry, I know that is a lot of thinking, ultimately creating a chain of connections that is rather tenuous, when taken altogether, and kind of speculative. But my point was to show some indication that Quercus emoryi likely isn't really that low in tannins compared to some of these other white oak species.

At least it's some reason to be skeptical about your view. You're basically the one who brought this up, by essentially saying "Quercus rugosa is nice, but I'm really more interested in this other completely separate species because it has more edible acorns."

When you did that, you opened the door up to me making an attempt to refute your comment, and point it out as (possibly, given limited available information) silly ignorant and senseless.

I think this all could be settled with a taste test.

Line up a "flight" of acorns from the subject species; something to cleanse the palate in between (perhaps some local fry bread); and a 1 - 10 scoring range from bitter/tannic to sweet/smooth.

I'll put a vote in for Quercus macrocarpa - local to these parts - whose substantial acorns I've tasted from a range of specimens around the Valley region.

What would a low tannin acorn even taste like? I suppose, at the very best, like a chestnut?

Taste 'em if you got 'em...

A Korean market near me sells acorn flour. Usually the acorn mash is rinsed multiple times with water to wash the tannins away. The flour can be used to make a porridge. "Sweet" low tannin acorns have to be used, since the water is unable to wash all the tannins away. It is possible to leach away much of the tannins with boiling water before pulverizing the acorns. It is then possible to eat them whole, but they are almost always ground to a flour.

Acorns are said to have a nutty flavor, also mild, a little bit "buttery" and mildly sweet, probably a little similar to chestnut but harder and more firm, a texture almost little bit like a harder peanut.

VV & Socal, the bur oak I have does have acorns w/a faintly nutty taste and no bitterness. Lately, tho, the ground harvest has diminished as squirrels have discovered the tree......

PS Ground-up nuts, acorns, etc are good simply added to your favorite stew or soups.

"Mexican Blue oak “Bellota” (Quercus oblongifolia) is found in association with Arizona white oak (Quercus arizonica) and Emory oak (Quercus emoryi) and it is an important constituent of pinyon–juniper communities – loads of great wild gathering in these semi-arid regions.

These are known to be the sweetest acorns of Baja, which also includes three other “sweet” acorn oaks: Netleaf oak “Encino Blanco” (Q. rugosa), Cape oak “Encino Negro” (Q. brandegeei), and the SW US and Mexican native, Canyon Live oak “Encino Roble” (Q. chrysolepis). All four of these acorns are important to indigenous cultures, still used in parts of Mexico, and sold in mercados."

“Sweet” Acorn Oaks – The Ecologist Cowboy

Why is there not a dedicated "Oaks" topic on here! Come on Gardenweb/Houzz, get with the Quercus Vibe!

How do you know when acorns are ripe?

They fall on the ground? ;-)

I actually tasted one of my bicolor oak acorns this morning.

It has turned brown and has loosened from the cap, barely hanging onto the tree.

It was on the sweet side when I nipped off a small bite with my teeth.

A little like chewing a raw peanut.

But as I bit off more and more, I could taste the bitterness increasing.

So, I spit the rest out and chalked it up to a scientific experiment. lol: