Friday, June 8, 2012

Don't be an Alice

In Lewis Caroll's Alice in Wonderland, Alice found that taking a bite out of a mushroom would make her grow very tall; the other side made her shrink.  At one level, this is a childrens' tale, or at another it could be argued to be about taking hallucinogenic drugs.

Unfortunately, if you don't know what you are doing when it comes to eating mushrooms, you can wind up taking a different kind of trip - to the hospital or the mortuary.

There are many mushrooms (fruiting bodies of fungi) that can be eaten.  At this time of year in New Zealand, the mornings are often damp and we see mushrooms and toadstools popping up all over the place.  In my opinion, field mushrooms, Agaricus campestris, have a much better, stronger flavour than cultivated mushrooms bought from the supermarket.  They are a delight to collect and eat and I have spent many hours walking around our small farm searching for these delicacies.

But how can you tell if a mushroom is safe to eat?  My grandfather told me that you should cook them in cream and eat them on toast for supper.  If you woke up in the morning, they were edible!  This is NOT the way.  Neither is peeling and cooking a way of making mushrooms safe - the toxins of many poisonous fungi, such as the Amanitas are not destroyed by heating. 

The only safe way to know if a mushroom is edible is to have a good knowledge of their appearance and where they are found.  There are guides to help you identify mushrooms and toadstools, but to the untrained eye, many different species look the same.  If you aren't sure, don't eat!

Even the terminology is open to interpretation.  Strictly, the word ‘mushroom’ refers only to the genus Agaricus.  The cultivated mushrooms sold in the supermarkets are usually the white buttons of Agaricus bisporus, though we do see other varieties, such as the large browns. The word 'toadstool' is then used to describe any other fruiting body with a cap and stem that appears different from Agaricus, often implying that it is poisonous.

I took the following from an ABC report that followed the death this week of a Chinese visitor to Australia who appears to have eaten Death Cap (Amanita phalloides) toadstools:

History:

  • Death cap mushrooms are considered the most poisonous in the world and one is enough to kill an adult human.
  • At least six people have died and at least 12 made sick from eating death cap mushrooms in Australia in the past decade.
  • Death caps have been involved in the majority of deaths around the world from mushroom poisoning, including that of Roman emperor Claudius.

Appearance:

  • Death cap mushrooms are similar in appearance to several species of edible mushrooms commonly used in cooking, such as paddy straw mushrooms and Caesar's mushroom.
  • Death caps may be white but are usually pale green to yellow in colour, with white gills and a white or pale green stalk up to 15cm long. (See image below from Wikipedia)
  • The entire mushroom is poisonous and cooking or peeling the mushroom does not remove toxicity.

Symptoms:

  • Death caps are said to taste pleasant and symptoms can occur six to 24 hours after consumption.
  • Initial symptoms can include abdominal pain, diarrhoea, vomiting, hypotension and jaundice, followed by seizures, coma, renal failure and cardiac arrest.

Habitat:

  • Death cap mushrooms can be found in parts of south eastern Australia, particularly ACT and parts of Victoria.
  • They are commonly found near established oak trees and some other hardwood trees and are most common during later summer to early winter after heavy rain or irrigation.
  • It is thought death caps were introduced to Australia with the importation of different hardwoods.

Treatment:

  • Death caps are extremely poisonous and if consumed it is a medical emergency.
  • Anyone who suspects they have eaten a death cap should seek immediate medical attention and where possible take a mushroom sample for identification.  
There are approximately eight toxins in A. phalloides, the major ones being α-amanitin and β-amanitin, which inhibit RNA polymerase.  This prevents protein synthesis, resulting in the death of cells.  The liver is usually the first organ to be damaged, often irreparably, and later the kidneys.
Picture of Amanita phalloides from Wikipedia:  http://en.wikipedia.org/wiki/Amanita_phalloides


Have a look at Peter Valda's comments on mushrooms and toadstools:

http://www.burkesbackyard.com.au/1997/archives/27/in_the_garden/gardening_tips,_books,_techniques_and_tools/mushrooms_and_toadstools


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