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roughbarked
Jackaroo
Joined: 23 Jan 2009
Posts: 301
Location: not far from the Black Stump.
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 Posted: Mon May 11, 2009 4:53 am Post subject: |
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Thank you Peter.
There should be more stated about such things. Comprehension about what we eat is paramount to avoiding illness.
For example there are several types of plant we may call spinach. Some have more oxalates than others.
Did I see someone say oxalis was clover?
First thing when tasting anything new. Take only a tiny portion and place it mouth and await a reaction.
The nectar from Eremophila flowers.. is sweet but beware.. it often contains ants.
Grevillea robusta nectar has never killed me but then such things take a fair bit of harvesting to get a decent amount.
Much better if you happen to know an Aboriginal whom actually engages in walkabout and living off bush foods. In that regard I am lucky.
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_ Any plant will grow from a single bud if you can replicate the required circumstances. |
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Thomas B
Dinkum Sheila
Joined: 04 Jan 2009
Posts: 159
Location: Canberra
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| Posted: Mon May 11, 2009 8:58 am Post subject: |
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Does anyone know the identity of the other plant toxins in Alocasia. After all, calcium oxalate crystals may hurt your mouth and gastrointestinal tract, but I doubt they could kill on their own. Apparently toddlers have died from eating the plant. These toxins apparently coat the surface of the crystals.
Also in Cherikoff's "The Bushfood Handbook" there is some misinformation about this plant. He suggests that the rhizome, after pounding and pureeing to break the calcium oxalate crystals, will be a calcium rich food. True, it will be rich in calcium, but still in a totally useless insoluble form. |
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PeterHardwick
Dinkum Sheila
Joined: 17 Jun 2006
Posts: 158
Location: Nightcap Ranges, NSW
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| Posted: Mon May 11, 2009 9:41 am Post subject: |
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| roughbarked wrote: |
| There should be more stated about such things. Comprehension about what we eat is paramount to avoiding illness. |
Couldn't agree me more. When it comes to broader popularization of wild food knowledge we need to have very specific toxicology information.
| roughbarked wrote: |
For example there are several types of plant we may call spinach. Some have more oxalates than others.
Did I see someone say oxalis was clover? |
ID confusion is an ongoing issue in amateur areas. Wild food professionals have to be ahead of the game, and be able to point-out the confusing species to newcomers.
| roughbarked wrote: |
| First thing when tasting anything new. Take only a tiny portion and place it mouth and await a reaction. |
Yes, and before that make sure nothing is eaten if its not thoroughly researched and identified as safe before hand. Even if its in mouth there's a risk that some toxins could pass through the mucous membranes in the mouth.
| roughbarked wrote: |
| Grevillea robusta nectar has never killed me but then such things take a fair bit of harvesting to get a decent amount. |
Again, the problem is the cyanogenetic glycosides in the flower itself and the allergy risk.
| roughbarked wrote: |
| Much better if you happen to know an Aboriginal whom actually engages in walkabout and living off bush foods. In that regard I am lucky. |
Thousands of years of use are a sure-bet for safety. The trouble is that seemingly "insignificant detail" might be very important and "get lost in translation" into popular Western culture. Aboriginal people do traditionally drink Grevillea nectar straight from the flower (more often via dunking the flowers in coolamons) - but the risk is with interpreting that as being safe for all Grevillea's - which it's not. And more uncertainty exists with the hybrid cultivars.
Also, it's worth noting that traditional safety information in one region might not apply to another region - because of possible phytochemical variation in the same species from to region. Just to keep us on our toes.
Last edited by PeterHardwick on Mon May 11, 2009 10:10 am; edited 2 times in total |
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PeterHardwick
Dinkum Sheila
Joined: 17 Jun 2006
Posts: 158
Location: Nightcap Ranges, NSW
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| Posted: Mon May 11, 2009 10:06 am Post subject: |
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| Thomas B wrote: |
| Does anyone know the identity of the other plant toxins in Alocasia. After all, calcium oxalate crystals may hurt your mouth and gastrointestinal tract, but I doubt they could kill on their own. Apparently toddlers have died from eating the plant. These toxins apparently coat the surface of the crystals. |
Thomas B, I'm reasobaly confident that you are right - that there is more to Alocasia toxicity profile than calcium oxalates, and I will get back to you on this with references when I track them down. But I think the primary assumption is that the toddler deaths is mainly caused by suffocation from throat swelling as a reaction to oxalate crystals.
Also, on Banksia toxicity - I'd be careful there as well, because I have a recollection on noticing some suspect benzaldyhyde type aromas in some species probably indicating cyanogentic glycoside. |
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PeterHardwick
Dinkum Sheila
Joined: 17 Jun 2006
Posts: 158
Location: Nightcap Ranges, NSW
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| Posted: Mon May 11, 2009 12:20 pm Post subject: |
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Just a correction on what I wrote before on warrigal greens, Tetragonia tetragonoides: the acrid flavour in raw warrigal greens IS likely to be calcium oxalates and not saponins; but the soapy beany flavour more likely to be saponins. So I'd suggest that there's two types of compounds picked up in the flavour of raw warrigal greens - which seem to be reduced by cooking.
By the way, even though oxalates may be present in warrigal greens, after 200 hundred years of use - there's been no recorded incidence of poisoning. That's why it's considered generally safe. From that, one would assume that the calcium oxalates (and saponins) in raw warrigal greens are reasonably harmless with occasional use. However, there is a soluble oxalate portion in there as well - and that could be a worry if one was eating too much raw warrigal greens. Hence, it's preferable to blanch warrigal greens.
Also, it would be reasonable to assume that the east coast strain of warrigal greens is fairly safe because it's one of the collections that was taken by Cook and Banks back to England, and subsequently distributed world-wide known as 'New Zealand Spinach'. Probably the NZ and Aus strains are very similar because the seed easily migrates on ocean currents.
However, with Hibiscus heterophyllus we have an incidence of poisoning and a warning from Aboriginal elders with regards to toxicity with over-use as a medicine - and no long term use as a vegetable by non-indigenous people.
It's likely that there's different proportions of soluble and insoluble oxalates between warrigal greens and H.heterophyllus.
Last edited by PeterHardwick on Wed May 13, 2009 12:26 pm; edited 3 times in total |
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eataust
Jillaroo
Joined: 11 Sep 2005
Posts: 999
Location: Tarago, NSW
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| Posted: Mon May 11, 2009 5:30 pm Post subject: |
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| PeterHardwick wrote: |
By the way. These been a bit of confusion with one of the earlier postings on this thread - where I'm quoted as writing a post (which was actually written by Eataust), supposedly quoting Thomas B (actually quoting me). And my original thread disappeared.
Gremlin's got into the thread. Hopefully it will get sorted soon
Cheers, Pete. |
I have had a look - I do have moderator rights in this thread - but while I can see what's happened, I'm not sure HOW. Essentially, a post I was making, which has lots of quotes in it, got edited into Peter's post, rather than added as a new post. Moderators can do that, but they need to click the correct button to do it, and it's located waaaaay away from the "reply to this post" button. You'd know if I actually did edit the post, because it would say "This post edited by a moderator".
Unfortunately, I don't know that there's a way to retrieve Peter's original post at this stage. I'll need to chat to the expert - Rimbaud - and see.
Sorry for the inconvenience!
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eat australia: grow it, find it, eat it: http://blog.eataustralia.info
Bushfood books - see my "website". |
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PeterHardwick
Dinkum Sheila
Joined: 17 Jun 2006
Posts: 158
Location: Nightcap Ranges, NSW
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| Posted: Tue May 12, 2009 11:34 pm Post subject: |
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Eataust, thanks for the insight on the forum gremlins.
Just reflecting on the cases of plant poisoning that I directly know of, and the toxin type responsible: two incidents of soluble oxalate poisoning (mega-dosing on raw spinach while fasting, and Hibiscus heterophyllus); three incidents of Alocasia oxalate crystals causing severe irritation of mouth and throat; two incidents of cyanogenetic glycoside poisoning (candlenut and Hicksbeachia pinnatifolia); one incident of alkaloid poisoning from Solanum aviculare; and an unknown toxin involved with a mass poisoning from Milletia megasperma when someone got the bright idea of putting the seed into bread.
Fortunately, none of these incidents were fatal. |
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PeterHardwick
Dinkum Sheila
Joined: 17 Jun 2006
Posts: 158
Location: Nightcap Ranges, NSW
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| Posted: Wed May 13, 2009 11:50 am Post subject: |
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Thomas B, coming back to your question on detoxified Alocasia potentially being a good source of calcium. The understanding of the absorption of calcium oxalates seems to be an active point of discussion in nutritional research - de Vries 1996: "Calcium is irreversibly bound to oxalic acid, so a food with an oxalate/Ca2+ ratio of 1 would not be a good calcium source, although it is a rich source of calcium."
However, more recent research on some poor old lab rats (Haines et al 1999) came to a new conclusion: "Thus, calcium bound as a small, neutral, calcium salt such as calcium oxalate does not have to be dissociated prior to absorption." Further: "These results alter our current understanding of calcium bioavailability from foods and therapeutic agents."
Ok, so now it turns out that insoluble calcium oxalate can be absorbed whole, but how does that provide calcium nuitritionally if it's still bound with oxalate - doesn't it just add to the total load of calcium oxalates in the blood that normally flush-out via urine when low amounts are involved?
And just to highlight that calcium oxalates are not readily destroyed via cooking, research (Savage et al 2006) on boiling or baking taro leaves shows that it made no difference to the calcium oxalate levels, but boiling reduced the soluble oxalates by 36%. One could also extrapolate this to warrigal greens.
By the way, be very careful of net medical references - a lot of internet sites on oxalate poisoning don't even seem to differentiate on the most basic level between soluble oxalates causing hypocalcaemia and the seperate effect of insoluble calcium oxalate crystals causing irritation.
Anyway, I'm done on calcium oxalates.
Cheers, Pete. |
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PeterHardwick
Dinkum Sheila
Joined: 17 Jun 2006
Posts: 158
Location: Nightcap Ranges, NSW
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| Posted: Thu Jun 04, 2009 3:17 pm Post subject: |
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I've just been viewing some more of these bush survival DVDs and material on Youtube, and it's much worse than I initially realized.
In one of the DVDs the "wild food expert" picks a flower head of Billygoat weed, Ageratum spp. (either A.houstonianum or A.conyzoides), and says something to the effect I don't know what this is, but it passes my edibility test, and proceeds to eat it.
The big problem is that Billygoat weed Ageratum is known to by very poisonous, containing a suite of toxins, including pyrolozidine alkaloids, coumarins and triterpenes.
The poisoning from Ageratum can be slow acting, causing necrosis in vital organs over time - including in the liver, lungs, stomach or kidneys.
Needless to say, the so-called "universal edibility test" promoted in the DVDs - supposedly being a way to work-out if an unknown plant is edible - is totally flawed because it only works on a window of 8 hours of self-observation - whereas toxins like triterpenes and pyrolozidine alkaloids can take many weeks or months before the onset of symptoms occur.
Anyway, I'm somewhat in shock that anyone could promote Ageratum as a wild food. |
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Thomas B
Dinkum Sheila
Joined: 04 Jan 2009
Posts: 159
Location: Canberra
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| Posted: Sat Jun 06, 2009 5:44 pm Post subject: |
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Peter, I was wondering if you know exactly what happened to the person who suffered after eating Solanum aviculare. It would be interesting to know the side effects of these alkaloids, for which the plant is actually farmed in Russia for the manufacture of contraceptives. |
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PeterHardwick
Dinkum Sheila
Joined: 17 Jun 2006
Posts: 158
Location: Nightcap Ranges, NSW
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| Posted: Sun Jun 07, 2009 12:29 pm Post subject: |
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Thomas, I can't remember all the details on S.aviculare poisoning - but I agree that it would be worth documenting. It sounded severe - but not sure if they were hospitalised. |
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