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Post by ottawagardener on Dec 19, 2014 7:10:00 GMT -5
Anyone ever do any testing on their creations especially tuberous ones like oca or potato for oxalic acid content and alkaloids respectively? I know you can taste them to a certain extent though they are stories that contradict that when it comes to the 'grey' levels.
Also, how about the chenopods. I am intrigued by Mike's nibbling on C. giganteum. This is a fantastic green and cover crop for me. Adding to its repertoire by selecting for seed production (actually it already produces in abundance) and/or edible flowering shoots appeals to me but I am not sure if it will have higher than considered acceptable oxalic acid content. Yes, eat diversely, you should taste it comments are acknowledged but I'd love to talk about this more in depth.
Also, just generally, for plants, does anyone test for nutrient content beyond proxies like colour?
I know the BRIX is pretty straight forward.
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Post by billw on Dec 20, 2014 14:19:16 GMT -5
With some guidance from Joseph, I have been able to test for oxalic acid content in oca, but I'm not completely satisfied with the procedure yet. To test for oxalic acid, you have to eliminate other acids that may confound the results first. My numbers appear to be too high, which means that there are probably other compounds still in the mix after extracting the malic acid and tartaric acid. So, I have a crude indicator of relative oxalic acid content, but will have to go back to the drawing board to figure out just what else is in the mix and how to extract it first in order to get a better absolute measurement. This will be the problem for many people in testing - not necessarily doing the lab work, but obtaining the knowledge necessary to design the test. Even if you know how to do the extractions to get down to the compound that you want to test, you may not be able to find any information about the chemical composition of the plant that you're working with. In some cases, that information will be available from academic sources and in others you won't have any choice but experimentation. Some basic info is pretty easy to test for, like moisture content, ash, total carbs, and even crude protein. Testing for mineral content from ash is usually pretty easy. Once you get into organic chem, many of the procedures become more difficult and expensive. Many require test gear that goes beyond and amateur budget. For example, I can do a titration to determine vitamin C content in a white fleshed potato, but for a potato with blue or red flesh it is impossible to determine when the titration is complete by eye, so you need a spectrophotometer. Other vitamins mostly require a well equipped lab. I found the book Food Analysis/Nielsen to be very helpful. If you can find information about which organic acids are present in large portions in Chenopodium, it should be possible to come up with a serial extraction. According to: www.phcogrev.com/article.asp?issn=0973-7847;year=2009;volume=3;issue=6;spage=280;epage=306;aulast=Kokanova-NedialkovaSo, there's a start.
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Post by ottawagardener on Dec 20, 2014 15:10:19 GMT -5
Thank you! That was a great start.
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Post by ilex on Dec 22, 2014 18:15:49 GMT -5
Have you tried meassuring ph of the leaves? Not really an oxalic acid test, but might be an indicator. Worth a try. You can usually tongue test oxalic acid, but you already know that.
Bug preassure can also be a good indicator. If they eat some more than others, bets are they are lower in compounds like oxalic acid.
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