The researchers found that white button mushrooms, the most commonly consumed kind in the U.S., have about 12 times more of the antioxidant than wheat germ and 4 times more than chicken liver, the previous top-rated ergothioneine sources based on available data. Until the Penn State researchers developed their testing approach, known as an assay, there was no method employing the most sensitive modern instrumentation and analytical techniques to quantify the amount of ergothioneine in fungi. The researchers say that their assay can be used for other plants, too, not just mushrooms.
Joy Dubost, doctoral candidate in food science, who conducted the study, says, "Numerous studies have shown that consuming fruits and vegetables which are high in antioxidants may reduce the risk of developing chronic diseases. Ergothioneine, a unique metabolite produced by fungi, has been shown to have strong antioxidant properties and to provide cellular protection within the human body." Dubost detailed the new assay and the amounts of ergothioneine in the most common and exotic mushrooms typically available in U.S. food stores in a paper presented today (Aug. 31) at the 230th American Chemical Society meeting in Washington, D. C. Her paper is Identification and Quantification of Ergothioneine in Cultivated Mushrooms by Liquid Chromatography-Mass Spectroscopy. Her co-authors are Dr. Robert B. Beelman, professor of food science; Dr. Devin G. Peterson, assistant professor of food science, and Dr. Daniel J. Royse, professor of plant pathology.
The Penn State researchers found that among the most commonly consumed mushrooms, portabellas and criminis have the most ergothioneine, followed closely by the white buttons. A standard 3-ounce USDA serving of these mushrooms, about the amount you'd put on a cheese steak or mushroom-topped burger, supplies up to 5 milligrams.
The exotic mushrooms have even more ergothioneine. The same standard serving size of shiitake, oyster, king oyster or maitake (hen of the woods) can contain up to 13mg in a 3-ounce serving or about 40 times as much as wheat germ.
Dubost notes that the levels of ergothioneine do not decrease when the mushrooms are cooked.
In developing their new assay, the researchers adapted an assay used to quantify the amount of ergothioneine in bovine ocular tissue. They used high performance liquid chromatography (HPLC), a UV-VIS detector and mass spectroscopy, instruments normally used in analytical chemistry.
The Penn State Experiment Station and Mushroom Endowment Fund supported the study. The Mushroom Council and NutriCore Northeast are supporting the Penn State's team's continuing research in this area.