<<Disclaimer: Verify this information before applying it to your situation.>>

Since the issue of gluten in mushrooms has popped up a couple of times
recently, I thought I'd check into this a bit more. 

 

I have grown mushrooms (shiitake, oyster, ganoderma) in the past, and am
familiar with how mushrooms are produced and how they grow. To confirm my
understanding, I spoke to the Quality Assurance manager at the Royal Oaks
facility for Monterey Mushrooms in Watsonville, California. 

 

Agaricus bisporus (button mushrooms, crimini, portabella) grow on a layer of
peat moss over the composted wheat straw, the only way the mushrooms could
come into contact with the wheat is by dust from other parts of the
operation somehow getting into the grow room and settling on the mushrooms. 

 

The mushrooms form on top of 4 inches of peat moss that is layered on top of
the wheat straw substrate. They do not push up through the substrate; only
the mycelium comes into contact with the substrate. The mushrooms themselves
never come into contact with the actual wheat straw. They are just the
fruiting body (reproductive/spoor producing part) of the mushroom "plant"
(mycelium) which has colonized the substrate (where the wheat straw is).  

 

The growing and harvesting are done in climate-controlled indoor rooms where
the air in the growing rooms is filtered, so dust from the wheat straw is
unlikely to come into the facility where the mushrooms grow.  The three
areas of the farm, composting, pasteurization, and fruiting, are all
separated by distances of 1/8 mile. The mushrooms, once picked, are in
closed facilities for all but about two minutes of transfer time. 

 

Unless the mycelium somehow manages to take gliadin protein from the wheat
in the substrate and deposit it unchanged into the fruiting body (which to
my understanding is not possible), I don't see how mushrooms could contain
wheat protein.

 

Shiitake are always grown on wood. They won't grow on straw. Oysters grow on
straw, but I wouldn't worry about it because of the reasons listed for
agaricus; the mushrooms themselves don't come into contact with the
substrate.

 

The QA manager said he'd have someone get back to me with more info, so if
you have further questions on this, let me know and I'll ask them when they
call back.

 

Pam


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