Mushroom growers have seen the light as more and more farms investigate the use of indoor light to enhance vitamin D content, following the lead of Dole and Monterey Mushrooms.

Plant pathologist Gary Schroeder, mushroom director for Dole, Kennett Square, Pa., saida two-millisecond flash of a xenon bulb is all it takes to give mushrooms 100% of the recommended daily value of vitamin D, currently 200-400 IU (international units) for adults.

A standard 3-ounce serving of white mushrooms provides about 4.5% of the daily value, making mushrooms the only naturally occurring plant-based source of vitamin D.

If scientists convince the federal government to increase the recommended daily value, Schroeder said it won’t pose a problem.

“If FDA says everybody needs 1,000 units, we can change the settings of our machine within about three minutes to deliver several flashes of light and have 100% of the new daily value,” said Schroeder.

Dole’s 6-ounce packages of portabella caps and slices are exposed to the light as they move along a packaging line.

“It’s like putting mushrooms in the sun,” Schroeder said, “and it adds a little shelf life.”

Monterey Mushroom Inc., Watsonville, Calif., has outfitted all its plants to pack the Vitamin D product, introduced just over a year ago in Sacramento. Vice president Joe Caldwell expected to roll it out to all East Coast customers by Aug. 1.

“Out technology is a little different than Dole’s,” Caldwell said.

“We’re still exposing the mushroom to natural light, but we use a softer, low voltage light source so we can do it for whites as well as browns.”

Monterey is selling washed and sliced whites and browns along with portabella caps and sliced, Caldwell said, and smaller quantities of whole 8-ounce whites and baby bellas.

“Vitamin D is very stable, even in cooking and freezing,” said Caldwell, “and we see 80% retention over two weeks. It’s a wonderful item as opposed to other nutrients.”

Highline Mushrooms, Leamington, Ontario, says it is about to become the first Canadian farm to launch vitamin D-enhanced mushrooms.

“We’ll be launching with 6-ounce portabella caps and sliced portabellas,” said chairwoman Elizabeth O’Neil.

“The nutritional facts table on each package will show that consumers can get their daily requirements of vitamin D, along with all of the other great nutritional properties of mushrooms.”

Ostrom Mushroom Farms, Olympia, Wash., is working on its own version of enhancing mushrooms with the sunshine vitamin, said Fletcher Street, director of marketing and sales.

Ostrom’s redesigned sliced portabella package should hit shelves in late fall or early 2011.

“It’s probably one of the most exciting innovations in the mushroom industry for a long time,” Street said.

“The equipment is readily available, but working it into your operation system is really challenging, which is probably why we all haven’t done it overnight.

“You’ve got to figure out how to get the mushrooms under the light so they’re exposed properly without damaging the mushrooms.”

Once Ostrom rolls out its products, Street plans to invite local media to the farm to see the process in action.

“We don’t want people to think we’re injecting our mushrooms with syringes,” she said.

Move over selenium

Mushroom’s superfood status continues to grow with new research finding yet another powerful antioxidant called ergothioneine.

Researchers at the Pennsylvania State mushroom research laboratory found that mushrooms contain significant levels of ergothioneine, which has antioxidant properties as a scavenger of strong oxidants.

Being heat-stable, it’s present in raw and cooked mushrooms.

Of the agaricus varieties, portabella and crimini mushrooms have the most ergothioneine, followed closely by white mushrooms. Exotic mushrooms such as maitake, oyster and shiitake have the highest amount.

Schroeder said it looks like mushrooms are the best source of this potential disease fighter.

“The science is not yet understood,” Schroeder said.

A new website,, brings together mushroom research reports from around the world, said Brittany Stager, marketing manager of Mushrooms Canada.