Tremella fuciformis, the snow fungus, an edible jelly fungus

Tom Volk's Fungus of the Month for January 2006

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 Dried Tremella fuciformis, from an Asian food store

It's January in Wisconsin, and January means snow! Since we can't find mushrooms here this time of year, we have to make do with mushrooms we've collected and preserved for the long cold winter. My kitchen is filled with dried and frozen mushrooms. However, if we've had a bad mushroom year, we can go to the store and buy some mushrooms! In most stores you can find a wide variety of fresh cultivated specialty mushrooms, such as Agaricus bisporus, shiitake, Oyster mushrooms, Hericium (the pom pon mushroom, a.k.a. the bear's head tooth fungus, Lion's mane, monkey head, or the icicle mushroom). and enoki. There are, of course, canned versions (yuk) of Agaricus bisporus in every store as well. In almost every large grocery store you can find dried shiitake, Oyster mushrooms, morels, and King boletes. If you live in a large enough city, you can visit an Asian foods store, where you can find a huge variety of dried and preserved mushrooms, including Agaricus blazei, Volvariella, netted stinkhorns and our fungus of the month, Tremella fuciformis, the snow fungus.

This month's fungus is in fact Tremella fuciformis, the snow fungus, sometimes called the silver ear fungus, the snow ear fungus or simply the white jelly fungus. The name "snow fungus" likely comes from its white color and more-or-less snowball-shaped appearance. It is edible and considered a delicacy in China and Japan. It does not have very much flavor, but the texture is very interesting, soft but crunchy at the same time. It's kind of rubber, but not in a rubber band sort of way. There are many ways to prepare this odd mushroom. It can be sautéed in olive oil and butter, just like a regular mushrooms (after rehydration, of course). Like all mushrooms, I prefer to have them browned and just starting to get crispy. I just had some for lunch, with eggs added to make an omelet, and it was delicious. A more traditional way of preparing this fungus is as a dessert! First, boil it slightly to rehydrate the fungus, drain off the excess water, and soak overnight in a sugary solution. My favorite way to do this is with the "heavy syrup" from canned "cling peaches in heavy syrup." then serve as a dessert, either with or without the peaches. Again, it's the texture that's very interesting. I like it, but it does get quite mixed reviews when I feed it to my students.

Tremella fuciformis, rehydrated from dried cultivated specimens

The snow fungus has been eaten for centuries in China, where it is considered to have significant medicinal properties, having been used against tuberculosis, high blood pressure, and even the common cold! From my other pages you may recall other fungi used in Oriental medicine, including Ganoderma lucidum (Reishi or Ling Zhi), Auricularia auricula-judae (the wood ear mushroom), Trametes versicolor (the turkey tail fungus), and various species of Cordyceps. There has been significant work by "western" medicine to corroborate the claims of Asian herbalists. This work with regard to Tremella is reviewed in a paper (Sergey V. Reshetnikov, Solomon P. Wasser, Ina Duckman, and Katherina Tsukor 2000. Medicinal Value of the Genus Tremella Pers. (Heterobasidiomycetes) (Review), International Journal of Medicinal Mushrooms 2:345-367.). They have attributed the medicinal effects of Tremella to the polysaccharide (long chain sugar derivatives) content of the mushrooms, especially acidic heteropolysaccharide glucuronoxylomannans. There seems to be some antitumor properties attributable to the stimulation of the immune system by these polysaccharides. In the abstract of their paper, these Israeli and Ukrainian researchers state:

"Tremella species also stimulate vascular endothelial cells; possess pronounced antiradiating effects; stimulate hematogenesis; demonstrate antidiabetic, antiinflammatory, hypocholesterolemic, antiallergic activities; and show hepatoprotective effects. Tremella glucuronoxylomannan can be recommended to improve immunodeficiency, including that induced by AIDS, physical stress, or aging, and to prevent senile degeneration of microvessels, maintaining better blood perfusion conditions in vital organs"

As I've stated preciously, most of these effects come from long-term consumption of the fungus. In the west this has spawned an entire "nutraceutical" industry. In this synergism between nutrition and pharmaceutical factors, the benefits are far different from either factor alone. I believe that these nutraceuticals are worthy of much more research.

Tremella fuciformis, from Wisconsin Before this mushroom could be cultivated, it had to be collected in the wild. In addition to that problem, wild versions of the fungus are rather small, only about the size of a golf ball. That, being coupled with its relative rarity, meant that only royalty or the very rich could afford to buy it. Since it was found growing on wood in nature, it was assumed that this fungus was using the wood for its nutrition. However, for many centuries Tremella eluded cultivation. So why can't it be cultivated on wood, like shiitake, Oyster mushrooms, the pom pon mushroom, or enoki? In the absence of wood, this species tends to grow as a yeast, adding another problem for potential cultivators, who threw out the subcultures as contaminants, thinking they had one of several hundred species of yeasts, such as Saccharomyces cerevisiae (the bakers' and brewers' yeast) or even Candida albicans. Eventually, studies in fungal ecology revealed that Tremella species are mycoparasites! This means that they don't eat the wood, but they eat another fungus that eats the wood. In this case, the host fungus is Hypoxylon archeri, one of the black Pyrenomycetes, related to Daldinia concentrica (carbon balls) and Xylaria polymorpha (dead man's fingers), all of which are wood decay fungi. It is possible that Hypoxylon archeri is not parasitized by the Tremella, but rather breaks down the wood into a form that can be used.

The process is relatively easy once you know the ecology of the growth. First the substrate is prepared, usually sawdust supplements with bran and some sort of grain, such as millet. This substrate is put into special plastic bags and sterilized. After cooling, the mycelium of Hypoxylon archeri is inoculated into the substrate and allowed to grow for a few weeks, at which time the Tremella culture is inoculated. After additional growth, the bags are put under fruiting conditions (high humidity and the proper temperature). A couple weeks later the snowball-shaped clusters of Tremella are formed on slits or holes cut in the bags. Most of the crop is dried for future sale, since the mushrooms rehydrate to almost exactly the same consistency and flavor as when they were fresh.

As I mentioned in a previous page, there are many other species of Tremella. Perhaps the most widespread in North America is Tremella mesenterica, witch's butter. You can see more pictures of jelly fungi on that page. Remember that jelly fungi have septate basidia that are unlike the entire basidia of "normal" mushrooms.

I hope you enjoyed learning about the snow fungus. It's an different sort of edible fungus with an interesting life cycle. You should try it when you get the chance.

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