Mushroom of the Week: The White Button Mushroom

The common White Button Mushroom is probably the most famous fungal fruiting body of them all.  It is found in virtually every grocery store in the world.  

Eaten raw, or cooked, it is an essential culinary delight, though somewhat flavorless as compared to its wild cousin, Agaricus campestris.  It goes by a huge variety of common names though its accurate species name is Agaricus bisporus with common names including, Pink Bottom, Meadow Mushroom, Swiss or Roman Brown Mushroom, Hot-Bed Mushroom, Field Mushroom or the French “Champignon de Paris.”

So, what is the difference between the varieties of it we see in the stores; the Cremini, Baby Bella and Portobella mushrooms?  

Well, they are all simply “varieties” of the exact same species of fungi.  That means they have different macroscopic features, as well as ages, but still contain the same DNA.  As they say in Thailand, “Same, same, but different!”

Crimini and Baby Bella’s are the same species but slightly different strains than the Portobello. They are harvested when the cap is still closed, or slightly opened, which keeps their flavor a little less intense.  For me, this is a good thing.  Their gills have started to mature and produce spores so they will be less pink and start to get that nice chocolate brown color that Portobello’s have.  

Their flavor is stronger than the white Button Mushroom, but not as strong as their steamroller cousin, the Portobello. Portobellos are large, fully mature Agaricus bisporus.  Their gills are a nice dark chocolate brown and their flavor is nutty, almost meaty, so they work very well as a meat substitute in, for example, a vegetarian hamburger.  Because of their large size they are also quite versatile to be stuffed or grilled and fill up a dinner plate.

If anyone thinks that mushrooms are inconsequential in terms of nutrition, think about that again.  In a large mushroom omelet, the white Button Mushroom provides you about three grams of protein as well as vitamins B1, 2, 3, 5, 6, 9, 12, C and D along with iron, magnesium, phosphorus, potassium, sodium, and zinc.

That’s a lot more than the average vegetable will give you!

White Button Mushrooms are grown in dark warehouses, caves, tunnels, or the catacombs of Paris.  Being decayers, or saprotrophic fungi, they need nutrient rich soil, called substrate, to grow in.  They are a second stage decomposer meaning that they do not decay the substrate directly like Shitake or Oyster mushrooms do, but require bacteria and other fungi to break the substrate down first.  This is a form of composting, and not just decomposing, because essential bacteria are involved.

Growing the common Button Mushroom is a six-stage process.

First, they make long rows of organic material about six-feet-high and let bacteria digest it for a week or two.  These piles heat up like anyone’s back yard composting bin would do.  They are turned and aerated while the bacteria produce ammonia, and the material starts to soften up and hold a lot of water.  This stage pasteurizes the soil and kills anything that could contaminate the spawn.  This is also why some people often turn and aerate their home composting bin, to keep the temperatures down and allow the gases to escape so they don’t end up with nice dark but completely sterile soil.

Second, they move the substrate to trays to allow it to cool a bit further and flush out the ammonia vapors.  The microbes that survive this process convert the remaining ammonia into protein, enriching the substrate.  All the ammonia must be gotten rid of in the end or it will kill the Agaricus mycelia once it is introduced into the substrate.

Third, the substrate cools further and the mushrooms are introduced having been started at a separate facility on sterile grain.  Growers can get all sorts of subtle varieties of Agaricus strains.  Those that produce white, off-white, cream, or brown capped fruiting bodies.  The heat and humidity are controlled to keep things moist and warm, but not hot.  So are the carbon dioxide levels.  A week and a half to three weeks will pass as the mycelia grow throughout the substrate.

Fourth, an inch or two of topping soil is added which locks in the soil moisture and spurns the beginning of the growth of the fruiting bodies called “pining.”  This takes only a few days to occur, and high humidity and very little light are the key to this stage.

Fifth, the temperature is decreased as are the levels of carbon dioxide and the mushrooms begin to grow.  This takes about two to three more weeks.

Six, the huge dense flushes of fruiting bodies grow to maturity in cycles of about three to five days each.  The substrate is exhausted after about three to five flushes of fruiting bodies have been produced from it and it can be recycled once again or used as garden compost.  Most Button Mushrooms are picked while their caps are still closed and attached to the stem, hence the term “button.”  

The complete process can take about three and a half months.

For any of the forms of the White Button Mushroom, other than the overpowering Portobello, I suggest sautéing them initially on a low temperature with a cover on the pan.  This allows them to sweat and cook without needing to add excessive oils or fat.

As they start to dry out, I add butter and uncover the pan so they can finish cooking and singe a bit.  A slight crispness, with a good bit of salt, on most mushrooms really brings out their flavor.  Try making an omelet with some prepared mustard mixed into the eggs, some grated gruyère cheese, crisp sautéed Button Mushrooms, salt, pepper, and a touch of tarragon.  And, voilá!