The False Morel Mushroom: Intriguing Chemistry and Biological Mimicry.

The false morel, Gyromitra esculenta

False morels are mushrooms that look like morels but which contain a toxin. One of the species, Gyromitra esculenta, for example, is a false morel that is apparently delicious. But if it’s not cooked properly, it can lead to vomiting and diarrhea. On occasion it could even kill consumers by affecting the heart, given that its poison affects nerves which control muscle coordination.

The first problematic compound is gyromitrin, named after the genus of Gyromitra esculenta. There are several reasons why the effects of eating the false morel vary so much, from having no effect to being mortal. For starters, the amount of the toxin can vary greatly from one mushroom to the other. The amount of gyromitrin in false morels can lie anywhere between 40 to 732 milligrams per kilogram of mushrooms (wet weight). Technically, gyromitrin isn’t poisonous in itself until it gets broken down in the stomach into acetaldehyde & monomethylhydrazine(MMH). Presumably not everyone metabolizes it the same way. But when enough MMH is formed, that compound, which coincidentally is a a rocket propellant that spontaneously ignites when it comes into contact with an oxidizer like N₂O₄, reduces pyridoxine and makes it ineffective. That’s a problem because pyridoxine is a form of Vitamin B6, which among other things, is needed to make neurotransmitters. That explains the poison’s ability to stop the heart.

Monomethylhydrazine. Each blue sphere represents a nitrogen atom; grey, carbon and white, hydrogen.
gyromitrin

 

In the 1950s, US pediatricians observed cases of an unusual seizure disorder in young infants. The usual anticonvulsants did nothing to abate the symptoms, but there was a dramatic improvement when vitamin B6 was given to them. Eventually, someone figured out that the babies affected were fed a commercial formula that contained only one-third the vitamin B6 found in other baby formulas. A manufacturing process reduced the pyridoxine content of the synthetic milk, just like mushroom-derived MMH does.

The toxic false morel, Gyromitra esculenta, and an edible true morel mushroom. Source: Wikipedia.

How one prepares the mushrooms also makes an immense difference to how toxic false morels can be. Airdrying is a good preliminary treatment, as that in itself destroys some toxin.  The bulk of the poison is then destroyed by heating. The ‘safest’ way to prepare Gyromitra species is to boil the mushrooms a couple of times (being careful not to inhale any of the vapors, which could contain the volatile toxin). The cooking water has to be thrown out, and then the mushrooms are to be fried in a separate pan. This removes the majority of the monomethylhydrazine.

In the early stages of growth, the true morel not only has the characteristic cavities, brain-like texture and color of the false morel, but it is also more spherical in shape, like its “impostor”. Is it an interesting example of Batesian mimicry, in which an organism, which is not poisonous, has evolved the appearance similar to those of non-poisonous species? The organism without the poison enjoys the benefits of carrying a poison and avoids being eaten but without having to invest the metabolic energy it takes to produce the poison.

Batesian mimicry: on the left is the non-poisonous mimic  Papilio polytes, which resembles the unpalatable Pachliopta aristolochiae (right). Source: Wikipedia

Several sources point out that “this mushroom is still consumed, despite its known carcinogenic properties”. But IARC has classified it as a group 3 carcinogen since 1987, which means that although it has shown some carcinogenic tendencies in some animals, there is no evidence that it causes cancer in humans. It’s best to focus on how to cook them, if one insists on eating them.

Other Sources:

Deficiency Diseases of the Nervous System Joseph Jankovic MD, in Bradley and Daroff’s Neurology in Clinical Practice, 2022

Journal of Chromatography A, 1125 (2006) 229–233. Mehrdad Arshadi and al.  Gas chromatography–mass spectrometry determination of the pentafluorobenzoyl derivative of methylhydrazine in false morel
(Gyromitra esculenta) as a monitor for the content of the toxin gyromitrin

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Romans, Kings, Plagues and Automobiles: Impact on Atmospheric Lead Levels

Source of graphic: GeoHealthVolume 1, Issue 4 p. 211-219
Colle Gnifetti in the Swiss Alps, where the ice core data was obtained

Courtesy of an analysis of 72-meter ice cores extracted from the 4450 meter high Colle Gnifetti in the Swiss-Italian Alps, the above graph reveals changing levels of lead(Pb) in the Earth’s atmosphere. The highest concentration occurred in the mid-1970s. This was about 50 years after refiners started to add tetraethyl lead to gasoline to make engines run more smoothly. Then from 1950 onwards car sales mushroomed, and so did traces of the lead they released. Luckily, by the 1980s, thanks to environmental legislation in both Europe and North America, unleaded gasoline sales rose while those of the toxic metal plummeted. By the 1990s, lead was no longer used in house paint, which caused its concentration in dust to drop. Consequently, as the graph reveals, by the late 1990s lead levels in the atmosphere had started to drop significantly.

Lead pipes

But what was the source of lead in previous years? Lead has been used for a long time to make pipes, coins, roofs, gutters, and cisterns. In the Middle Ages, the compound, lead acetate, was even used as an artificial sweetener. The amount of lead in the environment also tracks silver production because galena, lead’s ore, often lies side-by-side with ores of silver. So whenever lead or silver production peaked, the industrial boost would leave its signature in the atmosphere. In spring, especially, wind carried deposits of the heavy metal hundreds of miles from the mines of England to the Alps.

For example, the data reveals that lead-levels dropped around the year 1170, only to peak a few years later. What happened? For years King Henry II had been in conflict with the archbishop Thomas Becket. Eventually the latter was brutally murdered by the king’s knights. Henry II was excommunicated, people dodged taxes, and mining came to a halt. But when the king atoned for the murder by building many churches, since their roofs and gutters were made of lead, mines were busy and they spewed out more of the pollutant. Corroborating evidence comes from records of the spike in taxes on mines in the Peak District and at Carlisle in England.

From the New Yorker

What caused the most dramatic drop, around the year 1350? The lowest level in the last two thousand years coincided with the shutting down of lead and silver mines at the peak of the Black Death. Another drop in lead concentrations occurred in the mid 1400s. This time, production of the toxic metal plummeted during the The Great Slump, an economic depression in England lasting from the 1430s to the 1480s. The third sharpest drop in the amount of lead occurred in the late 1800s. This was related to the fact that in 1878, a fall in the price of lead and a general world economic depression caused smelting to slow down at some mines and come to a complete halt at others.

In the past, only economic disasters, murders or plagues could lower emissions of lead, and only temporarily. Now we could do it rationally and with a more lasting effect.

Sources:

Next-generation ice core technology reveals true minimum natural levels of lead (Pb) in the atmosphere: Insights from the Black Death. GeoHealthVolume 1, Issue 4 p. 211-219 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GH000064

Lead pollution in ancient ice cores may track the rise and fall of medieval kings. Science. 30 March 2020 Ann Gibbons. https://www.science.org/content/article/lead-pollution-ancient-ice-cores-may-track-rise-and-fall-medieval-kings

https://www.bbc.co.uk/bitesize/topics/zrfm7yc/articles/zmc6m39

Spaghetti Science

Ever run out of soup noodles and relied on breaking up spaghetti into small 1 to 2 cm pieces? That’s what I just did, and I never realized how many 1-2 mm fragments are generated with each and every break. In fact some bits were even smaller than a millimeter. I realized it by fluke because I was breaking the spaghetti with my hands inside a strainer, and the “dust” trickled through the sieve’s 3 mm holes, decorating the counter top. Here’s what it looked like.

It turns out that this has been common knowledge. Scientists have looked into it as well. According to a Smithsonian article,

To break it requires bending it into a bow shape. Eventually the force of the bend snaps the rod in the middle where it is most curved. But the physics doesn’t end there. That break releases energy back down the pieces of spaghetti in a “snap-back” wave or vibration. There’s enough energy in those waves to break off smaller lengths of pasta.

Jason Daley August 16, 2018

If you first twist the spaghetti, apparently, the “twist wave” travels faster than the snap, dissipating its energy. And the spaghetti breaks cleanly. But it would have taken a lot of impractical twisting in my case, given that I broke each strand several times while clumping several strands together to break them faster.

What goes on when spaghetti cooks? The chemistry part.

There are basically two parts to the process occurring between 55 and 85 oC. Water moves into the starch granules, causing them to expand. But for the pasta to fully cook, its protein has to react. If you have egg noodles, an insoluble network of egg and flour proteins form, trapping the swelling starch granules. A pH of 6, according to molecular gastronomist, Herve This, helps the proteins bind the starch even more firmly. One year I had my students test this notion by acidifying the boiling water with a tablespoon of lemon juice. Surely, enough it prevented the pasta from becoming sticky.

What if you have regular noodles? The same thing happens to the starch. But heat converts the flour’s globular proteins into relaxed chains. If overcooked the chains don’t trap the expanding starch, and its amylopectin diffuses out. As it clings to the surface of different strands, it binds them together. You end up with messy lumps of spaghetti.

Oddly, it never takes me the 10 minutes of recommended cooking time. Five seem to be sufficient to create a slightly al dente spaghetti. What’s also noteworthy is how the same recipe but different shapes of pasta creates a different taste, probably because of the role that texture plays in taste and because different shapes have different surface to volume ratios. Thus varying amounts of sauce cling to each noodle.

Recent research (2021) at the University of Parma in Italy confirmed that pasta is a medium to low-GI food, (glycemic index = GI). That’s related to the fact that the starch granules remain trapped in the network, and so they are not completely hydrolyzed in the small intestine. The GI was lowest for those pastas that were enriched with legumes or other plant based products.

Sources:

Herve This. Molecular Gastronomy. Columbia University Press. 2006

Exploratorium. Soaking Pasta. https://www.exploratorium.edu/food/soaking-pasta

Jason Daley. Physics Reveals How to Break Spaghetti Cleanly In Two. Smithsonian. 16/08/2016

Giuseppe Di Pede and al. Glycemic Index Values of Pasta Products: An Overview. Foods 202110(11), 2541; https://doi.org/10.3390/foods10112541