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Russula virescens

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RUSSULA VIRESCENS
Russula virescens (Schaeff.) Fr., Anteckn. Sver. Ätl. Svamp.: 50 (1836).

CARATTERISTICHE MORFOLOGICHE
CAPPELLO: 5-15 cm, compatto e carnoso, prima arrotondato poi convesso ed infine spianato; cuticola asciutta, opaca, separabile dal cappello solo lungo il margine, quasi sempre rotta in screpolature o areole poligonali, di colore verde-azzurrognolo o verde-oliva, colorazione che in qualche esemplare giovane può mancare; margine ondulato e liscio.
LAMELLE: fitte e fragili, scarsamente aderenti al gambo, forcate al margine, biancastre, spesso con macchie brune.
GAMBO: 2-8 x 2-6 cm., prima pieno poi spugnoso, pressoché cilindrico, a volte con macchie brune. La superficie si presenta un po' rugosa e forforacea nella parte alta.
Carne: soda, fragile e bianca. Frequentemente é preda di larve, specialmente nel periodo estivo. Odore: poco percettibile e lievemente fruttato negli esemplari giovani, leggermente sgradevole (come di "pesce") negli esemplari essiccati (ugualmente commestibili). Sapore: mite, dolce ed aromatico, come di nocciola.
SPORE: bianco-crema in massa.

HABITAT: fungo che cresce in estate-autunno, solitario o in gruppi, specialmente nei boschi di latifoglie, di rado nei boschi di conifere.
COMMESTIBILITA': la Russula virescens è considerata la migliore tra le Russule commestibili, insieme alla Russula cyanoxantha. A detta di molti è uno dei funghi più buoni in assoluto. Eccellente sia cruda che cotta. E' uno dei pochi funghi al mondo che è possibile consumare crudo senza correre rischi unitamente all'Amanita Caesarea ed alla Fistulina Hepatica.
Specie simili:
A parte alcune specie congeneri (come ad es. la Russula cutefracta var. pelterei, o Russula cyanoxantha var. pelterei) può risultare piuttosto pericolosa la confusione con alcune forme della Russula olivacea, che notoriamente è un fungo molto polimorfo: difatti chi ha l'abitudine di consumare la virescens cruda, rischia di avvelenarsi seriamente.
Amanita phalloides (mortale) per via del suo colore verdino e poiché spesso un'Amanita viene raccolta dagli inesperti troncandone di netto la volva, ossia eliminando il più evidente carattere distintivo tra un'Amanita ed una Russula.

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I COMPONENTI NUTRITIVI (THE NUTRITIONAL COMPONENTS)

The nutritional components of R. virescens mushrooms have been characterized. Fresh mushrooms contain about 92.5% moisture. A 100-gram (3.5 oz) sample of dried mushroom (100 g dw) has 365 kcal (1527 kilojoules). Carbohydrates make up the bulk of the fruit bodies, comprising 62% of the dry weight; 11.1% of the carbohydrates are sugars, the large majority of which (10.9%) is mannitol. The total lipid, or crude fat, content makes up 1.85% of the dry matter of the mushroom. The proportion of fatty acids (expressed as a percentage of total fatty acids) are 28.78% saturated, 41.51% monounsaturated, and 29.71% polyunsaturated. The most prevalent fatty acids include: palmitic acid, 17.3% of total fatty acids; stearic acid, 7.16%; oleic acid, 40.27%; and linoleic acid, 29.18%. Several bioactive compounds are present in the mushroom. One hundred grams (dry weight) contains 49.3 micrograms (µg) of tocopherols (20.0 µg alpha, 21.3 µg beta, and 8.0 µg gamma) and 0.19 milligrams (mg) of the carotenoid pigment lycopene. There are 4.46 g of organic acids per 100 g of dry mushrooms, including oxalic acid (0.78 g), malic acid (2.71 g), citric acid (0.55 g), and fumaric acid (0.23 g). Mushrooms have 22.6 mg/100 g dw of the phenolic compound 4-hydroxybenzoic acid, and 15.8 mg/100 g dw of cinnamic acid.

CHIMICA (CHEMISTRY)

Russula virescens has a limited capacity to bioaccumulate the micronutrients iron, copper, and zinc from the soil. The concentration of these trace metals is slightly higher in the caps than the stipes. A 300-gram (11 oz) meal of fresh mushroom caps would supply 16% of the recommended daily allowance (RDA) of copper for an adult male or female (ages 19–50); 16% or 7.3% of the RDA of iron for an adult male or female, respectively; and 16–22% of the adult RDA of zinc.[51] The mushroom is a poor bioaccumulator of the toxic heavy metals arsenic, cadmium, lead, mercury, and nickel.
Biologically active mushroom polysaccharides have been a frequent research topic in recent decades due to their possible stimulatory effect on innate and cell-mediated immune responses, antitumor activities, and other activities. Immunostimulatory activity, antioxidant activity, cholesterol-lowering, and blood sugar-lowering effects have been detected in extracts of R. virescens fruit bodies, which are attributed to polysaccharides. A water-insoluble beta-glucan, RVS3-II, has been isolated from the fruit bodies. Sulfatedderivatives of this compound have antitumor activities against sarcoma tumor cell lines. RVP, a water-soluble polysaccharide present in the mushroom, is made largely of galactomannan subunits and has antioxidant activity.
Ribonucleases (or RNases) are enzymes that catalyze the hydrolysis of ribonucleic acid (RNA), and collectively they play a critical role in many biological processes. A RNase from R. virescens was shown to be biochemically unique amongst seven edible mushroom species in several ways: it has a co-specificity towards cleaving RNA at poly A and poly C, compared to the monospecific RNases of the others; it can be adsorbed on chromatography columns containing DEAE–cellulose as the adsorbent; it has a pH optimum of 4.5, lower than all other species; and, it has a "distinctly different" N-terminal amino acid sequence. The mushroom contains a unique laccase enzyme that can break down several dyes used in the laboratory and in the textile industry, such as bromothymol blue, eriochrome black T, malachite green, and reactive brilliant blue. Laccases are being used increasingly in the textile industry as environmental biocatalysts for the treatment of dye wastewater.
R. virescens has a ribonuclease enzyme with a biochemistry unique among edible mushrooms. It also has biologically active polysaccharides, and a laccase enzyme that can break down several dyesused in the laboratory and in the textile industry.