By: Morgan Rease
My final quarter at UC Davis I tried something I hadn’t done before, but had heard about. People were always talking about how good it was, but I had never actually had it myself. College is when you try new things, right? Well here goes nothing…no turning back. I had heard about cotton-mouth before, but assumed it was a joke. HOLY CRAP, my mouth felt so dry. I thought I was having an allergic reaction. I can’t believe my so called “friends” encouraged me to do this. 60 seconds in and I was pretty sure all the moisture had already left my body. I didn’t want to die like that. Please don’t tell my mom.
Persimmons are no joke kids.
Isn’t fruit supposed to be sweet and delicious? Apparently persimmons didn’t get that memo. Without a doubt, an unripe persimmon is the most astringent thing I have tasted, and it’s a mistake I plan to only make once.But what’s the deal? Why so astringent? … And what the heck is a persimmon?
A persimmon (Diaspyros kaki L.) tastes a bit like a pumpkin crossed with an apple with the ripe texture ranging from a crisp peach to jelly. Persimmon season spans through Fall and Winter, with their unique flavor profile lending themselves well to warming desserts (like persimmon bread pudding). They are grown extensively in Asia, with China producing 74% of the global supply in 2011, Korea 9%, and Japan 4%. We grow some out in California too, but we’re small potatoes.
Other than just eating them, persimmons have some rather unusual applications. They can be used to detoxify snake venom, lower risk of cardiovascular disease, and recover gold particles from solution.[4, 5] So why are persimmons so strange? Persimmons, like oak, grapes, and tea, contain proanthocyanidins, more commonly known as tannins. The tannins from oak and grapes lead to the “fullness” of a wine and contribute mouthfeel. With persimmons, the mouthfeel created is one of a complete desert. But not all persimmons are astringent, only select varieties.
|Astringent Varietals||Non-Astringent Varietals|
|Nishimura Wase (seedless)||Maru|
Even non-astringent persimmons have tannins, but not nearly as much. Non-astringent persimmons have, on average, a mere 2.5% – 20% of the tannin content of the astringent varieties.
Chemical Basis for Astringency
Tannins belong to a class of compounds known as proanthocyanidins, making them antioxidants. Chemically, a tannin is a polymer built of flavan-3-ol monomers.
The term “tannin” is derived from the Germanic word for oak, a wood which was used for its tannins in the process of making leather, aka tanning leather. The transition from hide to leather is in part caused by the altering of the hide’s protein structure by the oak tannins. The reason that tannins cause you to perceive astringency is that they bind to, and precipitate, your salivary proteins. In fact, it is this protein binding ability that distinguishes tannins from other polyphenolic compounds.
Within your saliva are a variety of different proteins. The proteins at play in this case are collectively known as proline rich proteins (PRPs). These PRPs make up 70% of the salivary proteins. It is thought that the perception of astringency and the abundance of PRPs are a defense mechanism, as a diet heavy in tannins has been shown to be lethal in some animals.
So how does one avoid an unpleasantly tannic experience when it comes to persimmons?
Removal of astringency is referred to as “curing” and generally involves artificial ripening with ethylene gas. Some large-scale methods include: soaking in vinegar; submerging in warm water for 24 hours and then waiting an additional 48 out of the water; and submerging in boiling water and then letting sit for 12 hours; exposing the fruit to ethanol vapor for 10-14 days; and exposing the fruit to ethylene gas for 3 days.As ethylene gas is key to the ripening process, you can remove astringency at home by sealing your persimmons in a bag with a fruit that gives off ethylene gas, such as bananas or tomatoes, for 2-4 days.
Alternatively, you can wait for the fruit to ripen until it is soft like jelly. However, if the fruit is a non-astringent variety there’s no reason to wait.
- Nations, F.a.A.O.o.t.U., FAOSTAT, 2011, Food and Agriculture Organization of the United Nations: faostat.fao.org.
- Okonogi, T., et al., DETOXIFICATION BY PERSIMMON TANNIN OF SNAKE-VENOMS AND BACTERIAL TOXINS. Toxicon, 1979. 17(5): p. 524-527.
- Butt, M.S., et al., PERSIMMON (DIOSPYROS KAKI) FRUIT: HIDDEN PHYTOCHEMICALS AND HEALTH CLAIMS. Excli Journal, 2015. 14: p. 542-561.
- Parajuli, D., et al., Persimmon peel gel for the selective recovery of gold. Hydrometallurgy, 2007. 87(3-4): p. 133-139.
- Nakajima, A. and T. Sakaguchi, UPTAKE AND RECOVERY OF GOLD BY IMMOBILIZED PERSIMMON TANNIN. Journal of Chemical Technology and Biotechnology, 1993. 57(4): p. 321-326.
- Growers, C.R.F. Persimmon. 1996 [cited 2016 January 25].
- Giordani, E., et al., Selected primary and secondary metabolites in fresh persimmon (Diospyros kaki Thunb.): A review of analytical methods and current knowledge of fruit composition and health benefits. Food Research International, 2011. 44(7): p. 1752-1767.
- Hagerman, A.E., Tannin Chemistry, in Tannin Handbook2002, Miami University.
- Morton, J.F. Fruits of Warm Climates. 1987 [cited 2016 January 25].